Method and system for water purification by culturing and harvesting attached algal communities

A floway for cleansing water of pollutants is presented that has an upstream weir wherein water to be cleansed is admitted, a downstream weir wherefrom water is discharged, and curbs extending between the weirs for retaining water along the sides. The bottom surface is specifically textured conducive for growing a bed of algae to form an algal turf thereon. The algae bioassimilates pollutants from the water and is harvested periodically by a vacuum system having a notched, rotating nozzle at the intake end. An ultraviolet reactor positioned at the downstream end is used to degrade volatile organic compounds. In addition, the water surface is disturbed to change the angle of incidence of light and focus additional light energy on the algae.

BACKGROUND OF THE INVENTION 
The removal of chemical contaminants from wastewater and ground water has 
become an important problem in restoring ecological balance to polluted 
areas. It is known that some algal species are capable of absorbing heavy 
metals into their cell walls, thus reducing their toxic effects. Algae can 
also take up nutrients that may be present in overabundance, such as 
potassium and nitrogen, thus providing a remediating ecosystem. The system 
used to effect this uptake is known as algal turf. A further advantage to 
this technique is that the enriched algae can be harvested and used as 
animal feed, thus returning the nutrients to the food chain. 
Algal turf can potentially be used for a variety of applications. For 
example, the turf can be used to replace the biological or bacteriological 
filters in aquaria. As mentioned above, algal turf can be used to remove 
nutrients and other contaminants from polluted waters. Finally, by 
harvesting the algal mass, various process technique can be used to 
produce biomass as an energy source such as methane or ethanol, as a 
fertilizer or as a human or an animal food additive or supplement, 
cosmetic or pharmaceutical. 
Studies in algal turf production are known in the literature. For more than 
20 years, tropical reefs have been acknowledged to be among the most 
productive of natural systems. For example, in Lewis, "Processes of 
Organic Production on Coral Reefs," pp. 305-347, 52 Biol. Rev. (1977), 
production values as found, for example, on p. 312 therein, indicate that 
coral reefs are among the highest producers in primary production values 
for pelagic, benthic, and terrestrial ecosystems. 
Notwithstanding the values demonstrated in some earlier literature, recent 
efforts have demonstrated that those estimates of reef primary 
productivity were conservative. The mean reported value, 10.3 Gc/m.sup.2 
/day should be contrasted to values ranging from 19.2 to 32.7 Gc/m.sup.2 
/day in a 1980 study referring to St. Croix reefs. Such recent studies 
have demonstrated that algal turfs in conjunction with wave surge have 
been identified as the primary source of most reef productivity. The 
latest large-scale pilot plants in fresh water agricultural irrigation 
waters algal turf scrubbers or periphyton scrubbers with variable wave 
energies have repeatedly demonstrated production averaging 35 g/m.sup.2 /d 
with peaks well over 40 g/m.sup.2 /d. 
Within this technology it has been known that the removal or severe 
reduction of wave surge motion can reduce primary productivity, subtle 
manipulation of sometimes very light wave energies of various patterns 
across the growing surface can fine tune the performance of periphyton 
filters or algal turf such that a desired speciation of algal turf can 
dominate, and thus specific forms of a particular pollutant can be more 
effectively removed. In some areas such as reef systems, a typical daily 
cycle of oxygen concentration in a reef microcosm can be greatly affected 
by wave surge action. Reef production is accurately measured only near 
oxygen saturation, since atmospheric exchange is a factor at higher or 
lower oxygen concentrations. When a wave generator used in such reef 
microcosm devices is stopped, given the same current, light, and nutrient 
levels, net productivity is nearly zero. The lack of an oxygen spike when 
the wave generator is restarted indicates that greatly reduced production 
is a real factor as opposed to an apparent condition because storage has 
not occurred. 
Algal turf techniques have been disclosed in U.S. Pat. No. 4,333,263, 
issued to Adey, entitled "Algal Turf Scrubber," which issued Jun. 8, 1982, 
and the present inventor's U.S. Pat. No. 5,131,820, entitled "Low 
Pressure, Low Head Buoyant Piston Pump for Water Purification." 
Additionally, within the reported research in this technology there is a 
body of literature dealing with algal techniques for waste recycling, 
oceanic farming, or the like. Contemporary research can be grouped in two 
distinct categories: those utilizing macro algae and those using 
planktonic algae. In the first group, macro algae reports dealing with 
waste recycling or the like can be found in Ryther et al., "Physical 
Models of Integrated Waste-Recycling Marine Polyculture Systems," 
Aquaculture, 5, 163-177 (1975); California Institute of Technology, 
Graduate School Project "Evaluating Oceanic Farming of Seaweeds As Sources 
of Organics and Energy, "U.S. Department of Energy, Division of Solar 
Technology, Contract E (04-3)-1275; and Washington State Department of 
Natural Resources, Project "Aquaculture of Seaweeds on Artificial 
Substrates," U.S. Department of Commerce, Contract R/A-12. In the case of 
planktonic algae, Goldman et al., "Relative Growth of Different Species of 
Marine Algae in Wastewater-Seawater Mixtures," Marine Biology, 28, 17-25 
(1974); Karolinska Institute, "Investigation of an Integrated Aquatic 
System for Storing Solar Energy in Organic Material," Namnden for 
Energiproduktionforskning, No. 53 3065 062; and State of Hawaii Natural 
Energy Institute, "Energy from Algae of Bioconversion and Solid Waste," 
Hawaii State Government, demonstrate the status of contemporary research 
using that type of algae. 
In either case, research to date has not utilized wave surge motion as 
discussed herein to enhance the exchange of metabolites between algal 
cells in the water medium. Also, these known research techniques have not 
recognized the criticality of macro algae size, vis-a-vis the shading of 
one cell by another. Accordingly, such techniques are not suitable for 
optimum biomass production, and the propensity of removing nutrients and 
other contaminants from polluted waters is severely limited. 
Utilized in conjunction with this invention are micro algae of the major 
groups of benthic algae. In such algae, the use of attached algal turfs, 
wherein the simple algae all or most cells are photosynthetic, demands 
critical attention to wave surge motion. By optimizing such surge motion 
together with harvesting techniques, metabolite cellular-ambient water 
exchange is optimized, and continuous shading of one cell by an adjacent 
cell is prevented. 
Algal turf growth can be achieved in an aqueous environment by providing a 
suitable vacant area in which spores may settle. The first colonizations 
are usually microscopic diatoms, which are then rapidly dominated by the 
turf species. In accordance with the present invention, the harvesting of 
such turfs must occur before they are overgrown in turn by the larger 
macroalgae or macrophytes. This keeps production rates at a high level and 
minimizes predation by grazing microorganisms. The rate of harvesting is 
dependent on light levels, temperature, water culture nutrient 
concentration, micronutrient concentration, and surge action. Immediate 
regrowth of the algal turf will occur if the vacant surface or substrate 
is sufficiently coarse to allow a filamentous base of the algae to remain 
following harvesting. Typically, such a substrate can be a plastic screen 
having screen grid dimensions in the range of approximately 0.5 to 5 mm, 
or other highly textured surfaces. 
In the past, harvesting was accomplished by simply scraping the algae off 
the surface, but this often served incompletely to remove portions of the 
algae and allow these fragments and particles to be discharged into the 
water system, whereby the nutrients previously incorporated into plant 
mass or otherwise trapped were dislodged, decomposed, broken into small 
pieces, and flushed back into the waterway upon restart of process design 
flow rates. It was to improve upon the procedure of growing, harvesting, 
and processing the algae and other trapped particulates and organisms on a 
large scale (acres or more) and construction of facilities in an 
economical fashion, across various geological surfaces with low bearing 
pressures, which optimize growing conditions for the algal or paraphytic 
community and allow effective removal of bioassimilated or trapped 
pollutants after they have been taken up from the water, that the present 
invention was developed. 
SUMMARY OF THE INVENTION 
In accordance with this invention, a form of waterway is utilized, the 
bottom surface of which waterway is provided with a screen or other 
growing substrate conducive for growing a bed of algae to form an algal 
turf. This waterway is referred to as an algal turf floway, as it has a 
significantly longer flow distance and less wave surge action in some 
cases than in previously disclosed systems. The system elements permit a 
wide variety of algal turf or paraphytic communities with more flexible 
filtration capabilities than previously disclosed methods. By causing 
water from a lake, pond, river, or other waterway to flow over the algal 
turf, the water is cleansed to a sufficient degree that it can be 
reintroduced into the waterway in greatly improved condition. 
A longer floway than used in previously disclosed systems is desirable in 
that it promotes a hitherto unrealized benefit, a precipitation process, 
to be exploited that does not occur naturally. Previously used systems 
relied primarily on bioassimilation of the algae to remove pollutants. 
During the growth cycle, the algae consume carbon, which is provided by 
decaying material, the supply of which is never exhausted. With a longer 
floway and repeated harvesting, decaying material is removed, and the 
algae utilize other sources of carbon, such as bicarbonate. This causes a 
rise in pH, which in turn causes a precipitation of phosphorus and other 
compounds from the water. Aeration or addition of water to be treated 
returns the pH to normal levels. 
In the course of describing and claiming this invention, the term "algal 
turf" is to be construed not only as the filamentous algae, but the 
periphytic mat or community of matter that is allowed to or caused to 
exist with the filamentous algae. The latter includes but is not limited 
to: filamentous algae rooted by holdfasts on a surface; ephitic or 
clinging plants and animals that grow or are caused to grow from, or in 
the presence of, the filamentous algae, and the particulate matter trapped 
or otherwise detained in the course of manipulation of previously 
described elements; and/or all matter that can be removed from the floway 
via the harvesting process. 
Another term used herein that is to be construed in a broad way is "mature 
algal turf." By mature algal turf is meant the algal turf at a time or 
range of times at which its production reaches a point where, owing to 
size, development, or other reasons, a significant portion of the 
community comprising the algal turf becomes unstable physically and is 
released from its attachment and moves undesirably from its captive 
growing area such that it cannot be harvested. In many instances, the 
algal turf matures in seven to fifteen days, but the invention is not 
intended to be limited to this number of days. 
Another term utilized herein that is to be construed in a broad way is 
"sector." By sector is meant a lateral division of floway surface in its 
longest direction, whereby the algal turf of a selected longitudinal 
sector is harvested by means of laterally adjustable equipment. It is 
preferred that an even number of longitudinal sectors be selected on a 
floway such that travel both to and from a given point can accommodate the 
harvesting of algal turf. 
Still another term that is to be construed in a broad way is "curb." By 
curb is meant a divisional ridge of various height that serves many 
purposes such as structural support, division of algal turf treatment 
areas, as well as dispersed distribution of loads to underlying strata 
such as soft soil. The word "beam" may be interchangeably used to describe 
the curbs. Although the curbs may have constant elevation, causing a 
differential dimension between top of curb and sloped growing surface, a 
constantly sloping curb is preferred, mimicking the elevation of the 
floway such that there is no change in dimension from curb to floway from 
one place to another along the floway. This constant dimensional 
relationship is preferred to reduce or eliminate the need for elevational 
changes in the location of the intake plenum means used for removing 
mature algal turf from its growing surface. 
As will be seen hereinafter, for large-scale efforts the algal turf farm 
may be subdivided longitudinally into various floways, such as by 
separating walls extending substantially the entire distance between the 
means for admitting water into the floway at the upstream end, or inflow 
weir, and the means for discharging treated water at the downstream end, 
or outflow weir. Both weirs are movable between open and closed positions 
so that water can be admitted, held for preselected time intervals, and 
discharged when desired. Additionally the floways are divided into a 
number of sectors (two in the case described) that serve in description of 
the harvesting. Such an arrangement makes it possible for the algal turf 
floway to operate on a continuous basis, with the algal turf continuing to 
grow in some sectors during the time the algal turf in another sector is 
being harvested in a dewatered state. 
As is known, algal turf possesses the highly advantageous ability of being 
able to take up, precipitate, adsorb, or otherwise trap undesirable 
nutrients, contaminants, or minute particulate matter contained in the 
water, and to incorporate such nutrients into their plant mass and promote 
a periphytic community of superior particulate trapping ability. 
Accordingly, by causing the water to be treated to flow in a prescribed 
manner over the algal turf, the undesirable nutrients and pollutants can 
be removed from the water, with the treated water thereafter being 
permitted to flow back into the lake, marsh, or other waterway or basin in 
a greatly improved condition. 
A basic configuration of the algal turf floway, over which the water to be 
cleansed is caused to flow continuously (except for short durations at 
harvest), comprises an upstream weir, a downstream weir, and means 
defining the curb or sidewalls of the floway, also known as beams, for 
retaining water within the sides of the floway. Typically a first canal or 
pipeline brings water from the waterway to the location of the upstream 
weir such that predictable quantities of water can flow over or through 
the upstream weir and into the floway. After flowing over the algal turf 
for a suitable distance, the cleansed water then flows over the lower 
weir. There can be intermittent notched diversion tabs to trap filamentous 
algae and particulates as well as enhance mixing and prohibit 
channelization of water flowing down the floway between the inflow and 
outflow weirs. These tabs are rigid enough to accomplish the previously 
described tasks, but flexible enough so as not to require special 
consideration or repositioning of the vacuum intake during harvest. A 
second canal or pipeline is utilized to receive the water flowing over the 
lower weir, which second canal then delivers the cleansed water back into 
the lake, pond, river, or other such waterway. 
In particular sites the inflowing water may have an undesirably low pH. 
With the addition of calcium phosphate to the inflow water, as shown 
diagrammatically in FIG. 9, this situation can be remedied, while at the 
same time adding phosphorus, a primary nutrient for the growing algae, on 
the culture surface. An exemplary reaction for such a process is: 
EQU CaHPO.sub.4 +HX --&gt;CaX+H.sub.2 PO.sub.4 
Of course, the specific stoichiometry depends upon the composition of the 
waste stream. Calcium phosphate salts are useful because they are not 
soluble in water at circumneutral and alkaline pH values. It is likely 
that the phosphate salts CaHPO.sub.4, Ca.sub.10 (PO.sub.4).sub.6 
(OH).sub.2, and FeNH.sub.3 PO.sub.4 would be the most useful, with the 
iron salt having the added advantage of providing both nitrogen and 
phosphorus to the algal turf species. 
The advantage of using such salts is that these substances remain solid 
until reacting with an acidic waste stream. Their products reduce acidity 
while simultaneously providing nutrients required by the algal turf 
species. Calcium can react with metal ions to chemically precipitate a 
portion of the metals in the waste stream. The extent of calcium 
precipitation of metals will depend upon the pH, calcium concentration, 
and metal concentration. 
A suitable bottom surface is provided for the floway that is conducive for 
the growing of an algal turf thereon. This bottom surface may comprise 
plastic membranes and films, concrete, asphalt, or naturally occurring 
geologic features. These surfaces preferably have a suitable texture to 
provide protection from overharvesting, which can occur on smooth surfaces 
when the holdfasts are undesirably removed along with the mature algal 
turf. Conversely, there should not be voids in the surface such that 
organisms can find suitable domicile and undesirably eat and excrete algal 
turf as well as reproduce in numbers that limit the productivity of the 
algal turf communities ability to remove pollutants. There may, however, 
be small rodlike appendages in all or a part of the floway extending from 
the growing surface to slightly above the water surface to catch 
broken-off algal turf and reduce channeling. These remain on the surface 
during harvest and do not hamper the harvesting process. Examples of these 
surfaces may include, but are not limited to, rock formations, metals, 
wood, plastics, fiber-reinforced plastics, glass, ceramics, soils, woven 
or processed natural fibers, and higher-order plants. 
It has been demonstrated that an important relationship exists between the 
texture of the bottom surface and the colonization and harvesting 
efficiency of the algal turf system. Specifically, characteristics to be 
considered include texture amplitude and geometry, the spacing of textural 
elements in both the longitudinal and transverse directions, and the 
pattern, roughness, height, and distribution of the elements. Various 
textural elements can be used in combination, and such patterns tailored 
to the needs of a particular site, including the slope of the floway, the 
desired channeling patterns of flowing water, and the design of the 
harvesting apparatus. 
It is known that the cleansing function provided by the algal turf is 
assisted by having the lower algal turf filaments flashed with light, for 
this greatly assists the photosynthetic action of plant cells covered by 
algal turf or of organisms growing on top of them. To this end, a suitable 
means at a location adjacent the upstream weir is utilized for creating a 
variable surging action. This means is actuated periodically to cause a 
wave to pass substantially across all or part of the length of the floway. 
This surge can in some water systems serve to promote growth of more 
diverse types of algal turf, such as filamentous algae, on which other 
epiphytic or attached plants and animals can thrive. The surging can cause 
the algae to separate and articulate, thereby exposing more of the 
filaments to sunlight. 
Means are also provided for shading a portion of the water surface for 
providing at least two sectors, one subject to available solar 
illumination and the other shaded. This permits a variety of algal turf 
conditions, and thus a variety of cleansing environments. 
The surge can take place at different rates and magnitudes. Surges at least 
once per minute, but preferably approximately four to eight times a 
minute, can, in certain water systems, serve in a highly effective manner 
to stimulate the growth of specific species groups, leading to the 
optimization of the pollutant uptake ability of the algal turf. At some 
places on the floway the surge may not be readily detectable or even may 
be dissipated to the point where it is not detectable. 
In order to enhance the light intensity impinging on the algae, means may 
be used to disturb the water surface, changing the angle of incidence of 
the light on the water. By increasing the refraction-to-reflection ratio, 
additional light can reach the turf, improving growth. 
After a number of days of growth, the algal turf matures, and growth starts 
to slough off algal turf. Nutrients and pollutants incorporated into the 
algal turf begin to be rereleased into the water being treated. To harvest 
the algal turf actively, it is necessary periodically to remove and 
effectively to dispose of the relatively mature algal turf in order to rid 
the lake basin or other waterway of these undesirable pollutants. In other 
words, unless the mature algal turf is harvested in an effective manner, 
it is possible for the nutrients already taken up by the algal turf to 
find their way back into the waterway. Accordingly, it is an important 
purpose of this invention to utilize a highly improved system for removing 
the algal turf from the growing substrate to which it is attached, without 
resorting to a scraping effort that might well be counterproductive. 
Means are therefore provided for harvesting the algal turf, which is at 
least five days old, in a dewatered but wet state with almost all 
associated matter, except algal turf roots or holdfasts. This algal turf 
is removed in a manner not permitting any significant portions of the 
mature algal turf to remain in a dislodged and broken down condition such 
that it is flushed over the lower weir, and thence back into the waterway 
after harvest. 
The preferable means for harvesting the algal turf involves the use of a 
vacuum system that will remove substantially all of the mature algal turf, 
thus avoiding the situation often encountered in large-scale operations 
when utilizing a scraping action, where portions of the mature algal turf 
often remain and thereafter find their way back into the waterway. 
The vacuum intake plenum of the present invention comprises an orifice 
adjustable in elevation as well as positioning within a specific floway 
sector, such that the algal turf can be removed from that longitudinal 
sector. The lateral movement of this vacuum intake plenum can be 
accomplished by various means. As an alternative, a plurality of fixed 
vacuum intake plenums can be used for accomplishing the harvesting. 
The vacuum intake plenum in a specific embodiment may be equipped with a 
rotating brush/scraper element for removing algal turf bodies, leaving the 
roots or holdfasts behind. Compressed air and/or water can be sprayed at 
high pressure with or without the brush/scraper to dislodge certain 
micrograzers. The brush/scraper can have notches on the bottom edge, and 
these notches can be alternated so that only a partial harvest is effected 
on a part of the floway. Such an alternating pattern of notches can keep 
undesirable micrograzers under control, preventing an overpopulation of 
the growing surface, which would result in the micrograzers eating the 
algae and excreting the contaminants back into the water. 
In one form, the brush/scraper element rotates to dislodge the turf from 
the surface. A variety of designs and materials for this element, as well 
as a range of rotational speeds, have been tested to optimize harvesting 
efficiency. 
As discussed above, microinvertebrates left behind after harvesting can 
proliferate and consume significant portions of the mature algal turf and 
excrete pollutants previously absorbed by the algal turf. The 
brush/scraper element and bottom surface texture must be optimized to 
permit maximum removal of these organisms. Specifically, the elements are 
designed geometrically to cooperatively enhance destruction of unwanted 
organisms. 
A particular example of such an organism is the midge larva "chironomid, " 
a linear organism that builds a Quonset-hut-like shelter from algae and 
detritus. If the surface bottom texture and brush/scraper are designed 
with a linear geometry oriented transverse to the floway, the chironomid 
shelter is protected from removal by the harvester; however, if the 
elements are nonlinear, effective removal is possible. It has been found 
that air or water spray nozzles can be effective in removing chironomids 
from heavy-textured surfaces. The specific pressures are adjusted to avoid 
damaging the algal holdfasts. 
The present invention additionally comprises a method for controlling an 
undesirable microorganism population level in an algal turf floway. The 
method, which utilizes a floway as described above, comprises the steps of 
growing an algal turf on the bottom surface, the algal turf comprising and 
algal species and the undesirable microorganism population. Such an 
undesirable population may include such species as Chironomids. When the 
water is discharged from the downstream end of the floway, and the mature 
algal turf is harvested, instead of immediately refilling the floway, the 
culture surface is permitted to dry for a time sufficient to significantly 
reduce the population level of the undesirable microorganism but 
insufficient to eradicate the algal species in the algal turf. The length 
of drying time can be tailored to the specific organisms in the culture, 
but generally will range from 1 to 24 hours, depending on the rain 
conditions. 
A system without infestation by microinvertebrates can be managed without 
mechanical harvesting. In this case water flow turbulence causes a 
sloughing off of the mature algae, which are then strained out of the 
water after leaving the floway by means such as a continuous rotary 
strainer. This system, while it cannot offer the performance of the 
mechanical harvester discussed above, is very low maintenance. 
A desirable effect may be attained by constructing floways in series of two 
or more, water from the outlet of a first floway being directed to the 
inlet of a second floway, etc. Between the floways is positioned means for 
cooling the water and/or lowering the pH, preconditioning the water for 
enhanced scrubbing action in the second floway. These means are to treat 
the water entering the second (or subsequent) floway to reach optimal 
growing conditions for the specific culture growing in the floway. 
It has been shown that reseeding the floway surface with a desired species 
or mixed assemblage of plant and/or animal species can enhance the 
regrowth of the algal turf after harvesting and improve the overall 
performance of the system. Such a combination may include a filamentous 
alga and diatoms, which together can grow rapidly and fill the entire 
water column. 
An additional possible element of the purification system comprises means 
for degrading volatile organic compounds (VOCs) that may be present in 
contaminated ground water. In a particular embodiment this means comprises 
an ultraviolet reactor positioned downstream of the outflow weir of a 
floway. Ultraviolet light is known to promote degradation of chlorinated 
hydrocarbons such as trichloroethylene, trichloroethane, vinyl chloride, 
and others. The high oxygen and hydroxyl ion concentrations present in the 
outflow water aid in the removal of VOCs. 
It is therefore an object of this invention to provide an algal turf floway 
having specific textural characteristics capable of being constructed in 
many geologic soil conditions that is able to function in a low-cost yet 
highly effective manner to cleanse the water of a waterway, such as runoff 
to or from a basin, lake, pond, river or the like. 
It is another object of this invention to provide an algal turf floway 
capable of harvest when mature to effect removal of pollutants during this 
purification of the water, the floway designed to effect precipitation of 
contaminants. 
It is yet another object of this invention to provide a surging action in 
all or part of the floway, for causing a more diverse algal turf to 
develop, and to cause the algal turf to be flashed with light 
periodically. The water is also mixed, and physically nutrients and 
particulates are driven into intimate contact with algal cell walls, such 
that bioassimilation through photosynthesis and trapping action will be 
greatly enhanced by the algal turf. 
It is still another object of this invention to provide for the effective 
harvesting and removal of mature communities of algal turf in a dewatered 
but wet state by a vacuum pickup having a nozzle end tailored to optimize 
harvesting. 
A further object of the invention is to provide a method of reseeding 
specific algal species following a harvest. The species are selected to 
enhance the proliferation of at least one alga chosen for its efficacy in 
removing contaminants from a given site. 
Another object of the invention is to provide a system that does not 
require mechanical harvesting, but rather utilizes specific algal species, 
water turbulence, and filtering to remove sloughed-off mature algae. 
An additional object of the invention is to provide ultraviolet irradiation 
of the outflow water for degrading chlorinated hydrocarbons such as 
trichloroethylene. 
It is yet another object of this invention to provide a power-driven 
harvester device designed to roll along continuous grade beams or curbs 
that maintain a consistent flatness of surface or slight slope. 
It is another object of this invention to provide a floating barge to 
collect the algal turf harvest product as well as deliver the harvester 
from one floway to the next. The barge may have additional processing 
equipment on board to effect specialized biomass preparation as needs 
arise. 
It is a further object to provide a discharge hose onboard the power-driven 
harvester for conveying harvest slurry back to a holding barge or storage 
area, for greatly reducing storage requirements and lightening the wheel 
loads of the harvester on the support surface. 
It is another object of this invention to provide a water-impervious 
growing surface for prohibiting water saturation of the underlying soft 
soil, which can cause great reduction in the bearing capacity of the soil. 
It is an additional object of this invention to provide intermittent 
diversion means along the floway to limit flow channelization. 
It is yet a further object to raise the pH of incoming low-pH water to 
enhance algal growth. 
It is yet another object to intensify light impinging on the algal surface 
by disturbing the water surface. 
It is an additional object to improve the scrubbing effectiveness by 
placing two or more floways in series. 
These and other objects are satisfied by the present invention, a floway 
involving a growing surface of suitable texture for optimal algal turf 
production, located between a spaced pair of curbs, upon which algae can 
grow and form an algal turf, with a periodic surge of water being caused 
to flow along at least part of the floway, so as to increase algal 
metabolism, production, and species diversity, such that nutrients and 
pollutants contained in the water will be taken up, and particulates 
contained in the water trapped. 
The objects of this invention are also met with the method of the present 
invention for the purification water by natural means, utilizing algal 
turf grown on a suitable growing surface disposed between parallel, 
spaced-apart curbs, which algal turf is harvested, when mature, by the use 
of a harvester arranged to travel the length of such curbs, upon which 
harvester a vacuum intake plenum is utilized, with the disposal of the 
harvested algal turf being accomplished in such a manner as to prevent any 
entry of the algal turf into a waterway. 
These and other objects, features, and advantages will be more apparent 
from the drawing.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
With reference to FIG. 1, an algal turf farm 1 is located adjacent a form 
of waterway created for the continuous purification of water. A number of 
algal turf floways 2 are provided in which communities of algal turf grow 
under suitable conditions. Each floway 2 has an upstream end 302, a 
downstream end 304, a length 306, and a width 308. 
In one embodiment, each algal turf floway 2 is 22 feet wide and 750 feet 
long, these dimensions being linked to treatment parameters for one 
particular water system. The invention is not intended to be limited to 
any particular size or configuration of an algal turf floway. In general 
it has been found that the floway should be at least as long as it is 
wide. 
The length 306 of the floway 2 has also been shown to affect the 
performance efficiency of the system. As discussed, a longer floway that 
is frequently harvested has a limited supply of carbon to be 
bioassimilated from decaying material. When the algae then turn to other 
forms of carbon, such as bicarbonate, the pH of the system rises, and 
phosphorus and other compounds precipitate out from the water, permitting 
further cleansing action. The pH of the system may then be returned to 
normal levels with the use of aeration or an addition of ambient water to 
be purified. 
An exemplary floway length 306 would range between 100 and 10,000 feet, and 
a width from 1 to 50 feet, although these numbers are not meant to be 
limiting. 
As will be seen hereinafter, the invention may also be practiced on the 
scale of an algal turf farm 1 divided longitudinally into floways 2 by the 
use of separating walls or curbs extending substantially the entire 
distance from inflow weir 3 to outflow weir 4. Further, each floway may be 
regarded as being divided into sectors 5, as is to be seen on the left 
side of FIG. 1. 
In accordance with this invention, a harvester 22 moves along each of the 
floways 2, one floway at a time, with a vacuum pickup arrangement having a 
brush/scraper at the end for harvesting the mature algal turf in only one 
half or sector 5 of the floway during movement of the harvester 22 in one 
direction, and then for harvesting the algal turf in the other half or 
sector 5 during movement of the harvester 22 in the return direction. The 
details of the harvester 22 will be discussed in detail in connection with 
FIGS. 4a and 4b. 
One advantage of a divided farm is that harvesting of mature algal turf can 
take place in one floway that has been dewatered. Such is accomplished by 
virtue of the placement of an inflow weir dam 6 and removal of outflow 
weir sluice gates 7, which greatly diminishes flow and allows gravity to 
dewater but not dry the algal turf while full flow is continuing in other 
sectors. This practice greatly enhances the harvester performance with 
minimal water collection and greatly reduces algal turf processing effort. 
As shown in FIG. 1, the algal turf floway 2, over which the water to be 
cleansed is caused to flow continuously, may comprise an upstream or 
inflow weir 3, a downstream or outflow weir 4, and curb means defining 
sidewalls 8 of the floway. The sidewalls 8 may also be referred to as 
beams or curbs. A variety of sidewall 8 constructions is illustrated in 
FIG. 2a-e, having surfaces 100,200,300,400 and curb types 102,202,302,402. 
The sidewalls 8 are of consistent height so as to form the support for a 
harvesting vehicle mounted on wheels. The sidewalls are of sturdy 
construction and in some cases have relatively wide bases, so that they 
can distribute harvester loads over soft soils and not become displaced 
during use, even though supported over relatively low-bearing-capacity 
soils. A consistent spacing is used between each adjacent pair of 
sidewalls, so that the harvester 22 can travel therealong during the 
harvesting of mature algal turf. 
The upstream or inflow weir 3 can be of adjustable height, so that the flow 
of water over the weir can be carefully controlled. In addition, the 
inflow weir 3 may utilize articulation, such as, but not limited to, 
notches 9 placed at the top of the inflow weir so as to have a favorable 
effect upon the surging or spillage characteristics of this weir. As 
previously mentioned, the flow of water across the inflow weir 3 is 
preferably reduced just prior to and during harvest by placement of an 
inflow weir dam 6, and removal of outflow weir sluice gates 7, at the time 
the mature algal turf is to be harvested, so as to greatly reduce the 
water component and weight of the harvest wheel loads. 
A suitable bottom surface or growing surface 10 for the floway is conducive 
for the growing of an algal turf thereon (FIGS. 5a and 5b). This surface 
can be of a wide range of materials as long as the texture is such as will 
enable algal holdfasts (roots) to remain after harvest, while possessing 
the characteristics of compatibility with the harvest procedure, being 
able to withstand ultraviolet light, and being usable as a growing surface 
for an acceptable length of time. There can be rodlike pins spaced 
intermittently or in patterns extending from the growing surface to just 
beyond the water surface for catching dislodged algal turf. However, the 
surface should not be of such a nature as to permit algae-eating organisms 
to remain after harvest, for should such organisms reproduce in large 
numbers, their excretion of digested biomass would limit filtration 
efficiency. 
As may be seen in FIG. 2a and 2b, it is typically preferable to use 
materials such as high-strength polyethylene (HSPE) plastic or other 
plastic liners 100 in soft soil areas, as well as natural limestone 
formations, concrete, asphalt, asphalt/rubber, and polymer combinations. 
Note also FIGS. 2c, 2d, and 3. Again, these materials are exemplary and 
not meant to be limiting. 
FIGS. 5(a) and (b) illustrate a series of textural elements designed for 
use on bottom surface 10 of a floway. Each of these exemplary textures is 
used to optimize the purpose and population of an individual floway 
system, as well as the growing conditions. 
Typically a first or inflow canal 11 is utilized for bringing water from 
the waterway to be cleansed to a location adjacent the upstream or inflow 
weir 3. The inflow canal 11 can be unlined, or alternatively it may be 
lined with a plastic, wood, steel, or concrete liner, or a grout-filled 
mat or sheet pile system. In an alternate embodiment, a pipe or other 
means of conveyance may be used to bring water to the weir 3. The effect 
of moisture on soil characteristics and the availability of materials and 
skilled labor are usually the factors considered in the selection of these 
options. 
The substrate under growing surface 10 may be selectively dewatered by 
suitable dewatering pumps 21, which automatically pump water collected at 
subsurface intakes to surface locations to maintain moisture of subsurface 
soil. 
With regard to the water from the waterway to be purified, in some 
instances, water flows by gravity to the inflow canal 11 at a location 
adjacent the upstream or inflow weir 3, but in other instances, it is 
necessary to utilize a pump 12 and suitable piping 13 in order that 
predictable quantities of water can be provided at outlet 14 to the 
location adjacent the upstream or inflow weir 3. The pump 12 is preferably 
a centrifugal or axial flow pump, but the design of the pump is not of 
particular consequence to this invention. 
In particular locations, such as a Department of Energy site in Butte, 
Montana, inflow water can have extremely low pH values (here pH.about.2). 
At such low pH levels algae cannot grow. The addition of calcium phosphate 
to the water either prior to or immediately after entering inflow weir 3 
serves the dual purpose of raising the pH and adding nutrient phosphorus 
for the algae's consumption. 
After flowing over the algal turf floways 2 for a suitable distance, the 
cleansed water then flows over the outflow or downstream weir 4. Acond or 
outflow canal 15 receives the water flowing over the outflow weir 4, which 
second canal then delivers the cleansed water back into the lake, pond, 
river, or other such waterway. 
Because of the nature of the algal turf community, it is highly desirable 
to cause the water to be purified to pass in surges over all or part of 
the algal turf. One method to create such surges by the use of a 
periodically operating lightweight, buoyant piston as described in the 
present inventor's U.S. Patent No. 5,131,820. Here in FIG. 1, a 
wave-making device 16 in canal 11 is placed at the upstream end of the 
floway or growing surface, immediately upstream of the upstream weir 3, as 
well as in other inflow canals 11 such as in the canal at the top of FIG. 
1. 
As shown in FIG. 1, the wave-making device 16 may comprise a cable or cord 
17, which moves several floating volumes 16 that displace water and create 
a wake 18 when actuated in the general direction C-D of the cable or cord, 
similar to that from a boat. The cord is actuated by a power-driven wheel 
25 that has a means of alternately rotating clockwise and counterclockwise 
while wrapping the cable 17, causing float 16 to disturb the water, 
creating wave surge 18. By this arrangement, a suitable disturbance 18 is 
created in the inflow canal water surface, which translates into a 
desirable surging articulation of water entering each floway 2. 
Although a particular speed of operation is not to be taken as a 
limitation, it is desired that a surge of water pass over the algal turf 
of the floways at least once per minute, but more preferably the surge of 
water passes over the algal turf at least once every 15 seconds. These 
waves of water result in a desirable form of surge action, with the water 
passing over the inflow weir 3, causing nutrients to flow over and be 
driven into intimate contact with the algal turf. This enhances nutrient 
uptake by the algal turf through bioassimilation, and trapping by the 
algal turf. 
The preferred surging device is designed to articulate the water and affect 
the growth of certain and varying algal turf species that may dominate a 
portion of the growing area. Consequently different filtration objectives 
may support different surge rate and strength variations, and these 
variations can be manipulated to tune the algal turf floways to suit the 
water filtration objectives. 
For example, algae in high surge zones can tolerate greater flow variations 
such as a 1-10x increase over minimum algal turf community sustenance 
levels. This type of environment stimulates the proliferation of 
filamentous algae that are generally better suited to removal of reactive 
nutrients and pollutants. 
Water in low surge zones is capable of supporting more fragile plant 
assemblages as well as diatom proliferation and attachment. These areas 
are not as stable in variable flow environments, but they display optimal 
particulate trapping ability. The present invention is of sufficient 
breadth that various techniques may be utilized as are appropriate in a 
selected instance for a given water system filtration requirement. 
The preferred height differential between the inflow 3 and outflow 4 weirs 
is dependent upon the length 306 of the floway and the speed of water flow 
that is desired. The normal weir differential is in the range of 1 to 20 
inches, but this is not intended to be a limitation. In some locations, 
such as in a fallow field during harvesting, algal turf can be grown in a 
flooded location where virtually no slope is present and to a large degree 
the weir elevation differential is dependent on water flow rate. 
There is a desirable range of water depths 308 in the floway that is 
required to maximize the device performance. As an example, algae are 
rooted on substrate support algal plant canopies and epiphytic (clinging) 
plants and other organisms attached to plants that will grow to fill 
between 0.5 and 6 in. and up to 12 in. depth of watering. 
So while the desired depth of water in the floway is from 1 to 3 in., 
tolerances for the process have been shown to work satisfactorily up to 6 
in., and depths to 12 in. are acceptable in some places. The desired range 
of depth of water is from a minimum of approximately 1/8 in. up to 
something on the order of 6 to 12 in., as previously described, with the 
particular range of depths being brought about by a suitable manipulation 
of the weirs. 
As will be understood by those skilled in the art, water treatment occurs 
while the water is moving across the algal turf, at which time the 
pollutants come in contact with the algal turf or are otherwise trapped by 
organisms in the periphytic mat. Algal turf is a diverse and stable 
community with respect to production in all seasons and comprises many 
organisms, which can include that which is ambient in the water system or 
a modified plant and animal community achieved through inoculation of 
nonambient constituents. 
It is well known that an optimum uptake of nutrients is accomplished by 
algal turf that is from 4 to 25 days old, with it being preferable that 
algal turf that is approximately 7 to 15 days old be regarded as mature 
and therefore removed from the floway. The length of harvest is determined 
by monitoring the quantity of cells falling or sloughing of algal turf off 
the floway surface, and harvesting prior to high slough conditions with 
consideration of expected flow rates. As is obvious, care must be taken in 
harvesting the algal turf, for it is desirable for the remaining algae 
holdfasts to regenerate algal turf quickly. 
As mentioned, the water being purified continues flowing down the growing 
surface 2, in the direction A-B, guided by the sidewalls or curbs 8, and 
thereafter flows over the outflow or outflow weir 4, and thence into the 
second or outflow canal 15. From this canal, the treated water flows back 
into the lake or other waterway. It should be noted that a filter or a 
screen strainer can be utilized along with the intermittent flow diversion 
tabs 19 in conjunction with the outflow weir 4, so that algal turf slough 
may be captured and restrained from the outflow water. For example, 
closely spaced vertical pins 20 or a coarse mesh at the top of the outflow 
weir can hold dislodged algal turf filaments, which then can be gathered 
at harvest time. 
As mentioned when considering prior harvesting methods, mechanically 
scraping the screen or other substrate upon which the algal turf is 
growing often causes portions of the algal turf to be left behind, and 
thereafter carried back into the lake or other waterway. Accordingly, it 
is most important that the harvesting procedure serve effectively to 
remove pollutants absorbed from water and otherwise trapped by algal turf, 
leaving behind only the algal roots or holdfasts. If these pollutants and 
nutrients are to be prevented from re-entering the filtered water, it is 
advantageous to utilize a vacuum system such that large quantities of 
algal turf are entirely removed from the growing substrate, leaving only 
the roots or holdfasts attached to the substrate (FIG. 3a -d). 
Depicted in FIG. 1 is a harvesting barge 24 that not only serves to collect 
and store the considerably heavy harvested algal turf slurry and transport 
it via the outflow canal to a collective storage location, but also is 
equipped with means of lifting and moving the harvester from one floway to 
another floway so that harvesting can be executed on multiple floways with 
one harvester vehicle. The details of the barge 24 will be discussed at 
greater length hereinafter. 
It has been mentioned that an algal turf harvester 22 moves along beams or 
floway tracks in the harvesting of the algal turf. These beams or rails, 
one of which is depicted in FIG. 2a, are also known as the floway track 
grade beams 102. The beams are placed at a consistent spacing and serve to 
distribute harvest load to soft soil 112 over a wide area and reduce 
settlement and rutting by heavy wheel loads encountered with harvesting 
equipment. The beams also provide an anchor or attachment for the sides of 
the membrane 100 for algal turf growing area, as will be noted in FIG. 2a. 
These beams range in base width size from 12 to 72 in. for spacings of 10 
to 40 feet, and can be wider in larger applications. These beams are 
assembled such that they can be structurally contiguous via prestressed 
tension reinforcement strands 104 and structural splices 106 to the extent 
that harvester wheel loads do not cause high bearing pressure at beam 
splice points. 
Also shown in FIG. 2a is a fusion weld 110 of this plastic membrane 
material, with such a weld being commonly performed with equipment such as 
MUNCH tool Type U ii or Type E sold in the United States through Polyflex 
Corp. 
FIG. 2b shows a second method of attaching the edge of a membrane to the 
beam whereby a ringlet and flashing 150 as typically used on building roof 
parapet details is installed and has the advantage of venting such that 
gases that can build up under the membrane may be allowed to escape to the 
atmosphere. The grade beams or curbs are composed of precast, pretensioned 
high-strength concrete such as typically used in building construction and 
designed under standards of the Precast Concrete Institute and other 
organizations (see FIG. 2a). It may be advantageous in some conditions to 
utilize a means of maintaining the distance between or gauge of the 
concrete beams such as a tie strand or beam running perpendicular to the 
grade beams below the membrane. This concrete element is structurally 
sized by those skilled in the art after consideration of detailed site 
conditions, specifically soil-bearing capabilities and loading parameters. 
These parameters can vary with the moisture range of the submembrane soil, 
so for this reason the design of canals 11 and 15 should be strongly 
considered on analysis of this system. To control the soft soil moisture 
content further, dewatering pumps, or well points 21, are employed, as 
mentioned in conjunction with FIG. 1. These pumps are placed at intervals 
according to previously described issues, and serve to maintain a specific 
moisture content of soil, by pumping water from the submembrane area to 
the membrane surface, such that the conditions that support grade beams 
with stability may be safely maintained. Neither a specific size or 
configuration nor this method of soil moisture maintenance is intended to 
be limiting, as conditions are rarely the same in any two locations. 
The harvester 22 may be utilized either with a floway of the type depicted 
in FIGS. 1, 2a, and 2b, or in a more elaborate floway arrangement of the 
type depicted in FIGS. 2c, 2d, and 2e, which will be discussed 
hereinafter. 
The algal turf growing surface 62 may, for example, be a 60 mil 
high-strength polyethylene liner with heavy texture similar to that 
manufactured by Polyflex Corporation or Gundle Corporation and typically 
deployed for 20 years in containment of landfills or hazardous waste 
facilities. 
With reference to FIGS. 2c-e, it will be noted that these figures delineate 
other means and materials that can be used in the construction of floways. 
FIG. 2c shows a membrane scheme whereby HDPE (high-density polyethylene) 
200 is spread over finely graded soft soil 12, and a ditch is made to 
accept the end of membrane 200. The soil excavated fills trench 14, and a 
membrane-covered curb 202 is formed by fabric 200 and soil piled at edges 
of the floway. This type of floway requires a harvester that will span the 
soil formed curb and move on large rubber tires that bear directly on the 
soil some short distance outboard of the soil formed curb. Such rubber 
tires are common on agriculture equipment. In alternate embodiments, a hot 
asphalt rubber spray may be used on the membrane with reinforcing fibers, 
and also an aggregate texture surface may be used for the liner fabric. 
The schemes represented by FIGS. 2d and 2e are suitable only for 
higher-range subsoils conditions, natural or manmade. FIG. 2d is a simple 
asphalt growing surface 300 typically used for road pavement with an 
asphalt curb 302. This assembly is installed over a higher-strength stable 
compacted fill 304 in accordance with standard practices of the pavement 
industry. FIG. 2e shows a reinforced concrete growing surface 400 and a 
reinforced concrete curb 402 that act in the same basic capacity as the 
previously described asphalt scheme detailed in FIG. 2d. Both schemes 
delineated in FIGS. 2d and 2e would accept either type of harvester 
wheels. 
What is referred to as the vacuum intake plenum (or intake nozzle or 
pickup) is desirably between 1 and 6 in. wide and 2 and 50 feet in length 
with multiple pickups utilized on wider floways, and is preferably 
configured such that vacuum principles are employed to lift the wet algal 
turf off the growing surface (FIG. 3a-c). This is accomplished (FIG. 3a) 
by passing the orifice of the intake plenum 33 across the wet algal turf 
34 such that the harvest slurry 37 passes into close proximity with the 
orifice, and the algal turf is caused to be dislodged and moved by ambient 
air 38, passing to a low-pressure area 39. The air flow in cubic feet per 
minute is between 25 and 25,000, and the vacuum pressure is between 2.5 
and 250 in. of water, as measured in accordance with standards in the 
industry. The algal turf must come very close to (2 in. or less) or 
actually touch the orifice of the vacuum intake plenum to be adequately 
removed and conveyed. 
As shown in FIG. 3b, the orifice of the vacuum intake plenum may utilize a 
flexible scraper or brush to accommodate irregularities in the growing 
surface. A desirable harvesting action is achieved by the addition of a 
rotating scraper/brush 502 (see FIGS. 6a,b), which contacts the growing 
surface and serves to dislodge the algal turf. A notched scraper/brush 504 
(FIG. 6c) can be incorporated to provide a thinning-type harvest, the 
notch size and distribution being tailored to remove a desired amount of 
mature algal turf. Different notching patterns can be used in different 
harvests so that microinvertebrate populations can be controlled, while at 
the same time the average algal filament age can be extended beyond the 
basic harvesting interval of the floway. This thinning effect permits the 
filtration of the algal turf floway to remain more stable immediately 
after harvest. 
The notch depth 506 determines the amount of thinning and algal turf 
removed, the remaining, unharvested turf referred to as the "residual crop 
tissue mass." Exemplary notch widths are from 0.25 to 12 in., with a 
spacing 508 of 0.25-12 in. A notch width of 1 in. with a 1 in. spacing is 
particularly suitable for the filamentous communities, the 1 in. channels 
having been found to provide an optimal width for efficient distribution 
of water flow, mitigating the effects of major channelization of the 
periphyton growth. This notching also has the advantage of providing ample 
space between strips of residual crop tissue mass, which quickly 
reproduces back into the void, and thus enhances postharvest regrowth. In 
additional embodiments, multiple scrapers can be used with various 
notching arrangements, and they can be articulated in a direction 
perpendicular to the direction of harvester 22 travel (FIG. 6a). 
Another variable is the direction of rotation of the scraper/brush. In a 
particular embodiment, it has been found to be advantageous to rotate the 
scraper/brush in a direction counter to the direction of harvester travel. 
This direction serves to lift the material to be harvested into the vacuum 
stream of the harvester, which facilitates harvesting. 
The pattern of eddy currents induced by harvesting with a notched 
scraper/brush 504 has the further advantage of causing a desirable mixing 
effect, which allows a particular contaminant increased opportunity to 
contact the algae. It may be appreciated by one skilled in the art that 
the speed of the water flowing down the floway changes the resonant 
frequency, size, and rotational speed of the eddies. Thus the actual size 
and depth of the channel zone of harvest will depend on several factors, 
such as algal turf community, water speed, depth, harvest interval, and 
complex dynamic conditions that may be created by changing the residual 
crop tissue mass, speciation, or dominance of the algal turf community. 
As shown in FIGS. 3c and 3d, a bidirectional vacuum nozzle 36 may be 
actuated by a pressurized liquid system or other means that is brought 
into close association with the growing substrate in order that desirable 
quantities of mature algal turf can be more completely removed as 
previously described. 
With specific reference now to FIGS. 4a and 4b, wherein the vacuum pickup 
or vacuum intake plenum is at 40, is shown a preferred embodiment of an 
algal turf harvester 22, designed to roll along beams or rails or curbs 60 
that are placed in a parallel relationship in a direction coinciding with 
the direction of flow of the water through the floways 2. 
The harvester 22 is preferably powered by an internal combustion engine 54, 
although in some instances an electric motor powered by a nearby ground 
installation could be used. As will be noted from FIGS. 4a and 4b, the 
engine 54 is operatively connected to drive a hydraulic pump 56. The 
hydraulic pump 56 serves to supply highly pressurized fluid for driving 
the harvester movement drive motor 58. The drive motor 58 is suitably 
connected to the wheels 59 designed to drive belt tracks 61 such that they 
move along the beams or rails 60. 
Both directions of harvester travel are used to vacuum harvest the algal 
turf; that is, the harvester operates bidirectionally. Directional change 
of the harvester as well as other adjustments in travel speed and tuning 
the position of vacuum pick up are done by a skilled equipment operator 
who adjusts controls as needed. The wheels 59 are provided with shoulders 
on both sides extending beyond the belt surface to the sides of the beam 
so as to prevent the harvester 22 from becoming derailed. 
The hydraulic pump 56 also supplies highly pressurized fluid for driving 
the pump 48 serving to remove mature algal turf from the floway, and to 
deliver it to an algal turf harvest slurry transfer hose, depicted as hose 
reel 50 in FIG. 4a and 4b. This hose is deployed behind the first sector 
of a given floway, from which algal turf is harvested on the first pass of 
the harvester, with the hose being rewound upon return of the harvester to 
its starting place in that particular floway. FIG. 1 delineates this 
evolution taking place in two passes along a floway, one forward and one 
back, although this two-pass, two-sector floway is not intended as a 
limitation. 
With regard to the means provided by which the harvest vehicle is caused to 
move along the floway rails, FIG. 4a depicts fluid-powered motor 58, which 
rotates a shaft drive system with intermittent low-friction bearings to 
accomplish this conveyance of the harvester. 
Also powered with pressurized fluid supplied from the hydraulic pump 56 are 
vacuum blower 46 and the vacuum pickup 40. Vacuum intake or vacuum intake 
plenum 40, typically of the type depicted in FIGS. 3c and 3d, is a 
bidirectional pickup, comprising a horizontally oriented cylinder with a 
slot at the bottom, although other shapes can be utilized with or without 
rotating or stationary scraper/brushes. The intake 40 is placed such that 
vacuum principles as previously described can be optimized. This vacuum 
intake plenum device or vacuum pickup arrangement causes the algal turf to 
be detached and conveyed from the growing surface to the separator 44. 
As to other pickup details, in the illustrated embodiment, the vacuum 
pickup 40 is equipped with suitable means of actuation both about the axis 
of the cylinder for 10-45 degrees (see FIGS. 3c and 3d) and laterally in 
the direction of the cylinder axis via a track and wheeled mechanism 41 so 
that it can be moved via hydraulic motor and chain from one side to the 
other side of the harvester, in order that the algal turf community on 
both sectors of a given floway can be harvested. This is also referred to 
as the relocation mechanism of the intake plenum. It is to be noted from 
FIG. 4a and 4b that a ghosted location 42 is used to indicate the movement 
of the intake plenum or vacuum pickup 40 that is possible in accordance 
with this arrangement. 
The cross-sectional area of the separator 44 is considerably larger than 
the area of the duct from the pickup 40, and this causes a drop in air 
velocity, which effects the separation of the liquid algal turf harvest 
slurry from the air previously conveying the slurry. The air continues to 
the vacuum blower 46 through the duct shown and is exhausted upward 
through the blower outlet 47. The blower 46 is visible in FIGS. 4a and 4b 
and may, for example, be a Chicago Blower model Lo 15 single-inlet, 
self-cleaning, reverse-inclined, radial tip, heavy-duty, vacuum blower, 
which is driven by a suitable hydraulic motor. There are many other 
manufacturers, types, and sizes of suitable blowers that may be utilized 
on the harvester 22, and such blowers could be powered by various means. 
The harvest slurry picked up by the vacuum pickup or intake plenum 40 
enters the separator 44, which separates air from the algal turf harvest 
slurry. The slurry then falls by gravity to the cone-shaped bottom 45 of 
the separator (FIG. 4b). From this location the slurry is conveyed by pump 
48 into the harvest slurry transfer hose stored on hose reel 50. This hose 
reel is configured with a swivel fitting 49 at the inlet such that it can 
effect transfer of algal turf harvest slurry from pump 48 during 
deployment and rewinding evolutions. The hose reel 50 may have an indexer 
52 to ensure orderly placement of the hose on the reel, and the reel is 
equipped with a pressurized fluid or other means of restraint 55 from 
unwanted movement during flow variation of pump 48 or movement of the 
harvest vehicle along the floway path and to wind the hose back on the 
reel during the return pass back to the harvest starting point at the 
outflow weir as previously discussed. 
The end of the hose 52 is plumbed to a harvest barge 24 or to a similar 
storage or processing location some varying distance from the moving 
harvester. This collection point can optionally be equipped with a suction 
pump to enhance flow through the transfer hose. 
The harvest barge 24 may be operatively utilized upon outflow canal 15 
(FIG. 1). The harvest barge 24 may serve many purposes, such as to contain 
and convey the considerably heavy algal turf harvest through buoyant means 
to a collection site and to make possible a relocation of the harvester 
from floway to floway such that one harvester can harvest a large number 
of floways. Additionally, on-barge processing of algal turf, such as 
further dewatering, drying, and packaging for specialized uses, may be 
carried on in many instances. Such uses include soil additives, 
fertilizer, human food, animal feed, cosmetic and pharmaceutical products, 
and related industrial products. 
A remotely powered motor via reeled cable or a motor generator set could be 
used in lieu of the engine hydraulic combination to drive components on 
the harvester. 
The moving harvester 22 with an onboard spool of hose can feed out hose as 
the harvester moves along a floway to collect the algal turf harvest from 
the growing surface. By the use of the harvester, the operator can remove 
mature algal turf from one half of the width of the floway 2 during 
initial travel in one direction, and then remove mature algal turf from 
the other half of the floway during the return trip. The invention is not 
limited to a floway being divided into only two longitudinal sectors, for 
four or six or possibly even larger number of sectors could be utilized. 
The hose may be fed out as the harvester moves away from the barge, and 
then retrieved on the return trip, as the harvester moves back toward the 
barge. It is undesirable for the hose to be deployed over an unharvested 
floway sector, as this would break up and dislodge the algal turf, 
effecting harvest completeness. 
As previously discussed, the harvesting barge serves not only to collect 
and store the heavy harvested algal turf slurry and transport it via the 
outflow canal to a collective storage location, but it is also equipped 
with means of lifting and moving the self-powered harvester from one 
floway to another floway so that harvesting of algal turf can be 
accomplished on multiple floways by the use of only a single harvester 
vehicle. 
In normal practice, it is highly desirable in the instance of a large 
installation to subdivide the algal turf farm longitudinally into multiple 
floways, each with at least two sectors. As depicted in FIG. 1, numerous 
floways extend at right angles to inflow canal 11, with an outflow canal 
15 being disposed at the ends of these floways. These individual floways 
can be created by the use of separating walls or curbs extending 
substantially the entire distance between the inflow canal 11 and the 
outflow canal 15. 
Floways may also be constructed in series of two or more (see FIG. 10), 
with the outlet 902 of a first floway 92 in fluid communication with the 
inlet 904 of a second floway 94. Between the floways is positioned a means 
for cooling the water and/or lowering the pH. Such means may comprise a 
coarse gravel filter 96, which would cool water passing therethrough. 
Other means may include a cooling tower or a gas scrubber. Additionally, 
such means may include a biological means for lowering the pH, such as 
bacteria that will absorb excess oxygen and release carbon dioxide, which 
will lower the pH of the water. This filtering preconditions the water for 
enhanced scrubbing action in the second floway 94. 
As mentioned, it is advantageous to restrict inflow during harvesting of a 
given floway 2, so that harvest water content can be minimized. 
It has been found to be beneficial to provide a refuge-type area, or 
seeding channel 97, at the top of the floway 2 (FIG. 8a,b). This area 97 
is harvested less frequently than the remaining portion of the bottom 
surface to allow highly reproductive plants to reseed the growing surface. 
Means are also provided for reseeding the floway surface with a specific 
catalyst species or mixed assemblage of species (see FIG. 8a,b). This 
reseeding has been shown to enhance the growth of the algal turf after 
harvesting, improving the performance of the system. A specific 
combination is a filamentous alga plus diatoms, which together can grow 
rapidly. With reference to FIG. 8, material is added to a seeding channel 
97 located adjacent inflow weir 973 in floway 98, which has a bottom 975 
sloping downward toward outflow weir 974. Seeding channel 97 is delimited 
at the downstream end by porous reseeding weir 976, having a mesh size 
dimensioned to permit water to flow therethrough. Large clumps of algal 
biomass are retained within the weir 976, while small filament strands and 
algal spores are washed down the floway, where they settle out and attach. 
An exemplary mesh size is 0.25 in. mesh, with a 0.7 in. pore size. 
An algal seed stock may also be added to the floway surface following 
harvesting to enhance treatment efficiency and maintain species diversity 
or a dominance of a particular species. This reseeding can be accomplished 
from the harvester itself. 
In order to provide different growing environments for the algal turf, an 
anaerobic digester 95 is provided (see FIG. 1), typically adjacent the 
upstream end of the floway 2. A first portion 952 has a first depth 308 
that is sufficient to promote aerobic growth. 
A second portion 956 is adjacent the upstream end and has a second depth 
958 greater than the first depth 308 that is sufficient to promote 
anaerobic growth. 
In use, water is admitted into the floway by the inflow weir 3 and is 
permitted to flow over the algal turf. The bottom surface first portion 
952 of the algal turf serves as a means for aerobically bioassimilating 
pollutants from the water to be treated, and thereby cleanses the water 
thereof. The bottom surface second portion 956 of the algal turf serves as 
a means for anaerobically bioassimilating pollutants from the water to be 
treated, and thereby cleanses the water thereof. Finally the water is 
discharged from the ouflow weir 4 in a cleansed condition. 
Quite advantageously, the arrangement illustrated in FIG. 1 enables mature 
algal turf in one section to be harvested by shutting off the water 
thereto, while permitting the water to continue to flow through the other 
sector or sectors. The multisector arrangement thus makes it possible for 
the algal turf farm to operate on a continuous basis, with growth 
continuing in all the other floways during the time that the algal turf in 
one or more floways is being harvested in a dewatered state. As should now 
be apparent, in accordance with one embodiment of this invention, the 
intake plenum means are movable laterally on the harvester, so as to be 
selectively positionable in any of several possible positions. Because the 
floway may be regarded as divided into a plurality of longitudinal 
sectors, as the harvester moves along the curbs and over the floway, 
mature algal turf can be harvested from a selected longitudinal sector of 
the floway, as determined by the lateral positioning of the intake plenum 
means. On the return trip, the mature algal turf can be harvested from a 
different longitudinal sector of the floway. 
As an alternative to the foregoing embodiment, the intake plenum means may 
involve the use of at least two intake plenums that are disposed in 
laterally fixed locations on the harvester, with each intake plenum being 
relatable to a corresponding longitudinal sector. In order to be able to 
utilize relatively modest vacuum intake means, it may be preferable to 
utilize means for selectively activating these several intake plenums, so 
that not all are operating at the same time. Therefore, as the harvester 
moves along the curbs and over the floway, mature algal turf can be 
harvested from each selected longitudinal sector of the floway, as 
determined by the position of the particular intake plenum. 
When using the laterally fixed intake plenums, it may be desirable for the 
operator to accomplish a slight vertical repositioning of the intake 
plenums, depending on the particular sector being harvested at a given 
time. In this way the proper tolerance can be maintained between intake 
plenum and algal turf growing surface. 
As indicated earlier, it is known that the cleansing function provided by 
algal turf is assisted by having the lower algal filaments flashed with 
light, for this greatly assists photosynthetic action of the plant cells 
covered by turfs of organisms growing on top of them. To this end, a 
suitable illumination means 86 is positioned above the water surface for 
creating a high-intensity source of energy usable by the algae for 
photosynthesis, enhancing growth potential. To capitalize further on this 
additional light energy, means 87 are provided to disturb the water 
surface, permitting the refraction at the water surface to "focus" light 
onto the algae. As can be seen in FIGS. 11 and 12, waves cause additional 
light to enter the water, since light at an angle greater than or equal to 
60 degrees is largely reflected off the water surface, and waves serve to 
change the angle of light incidence at the surface. FIG. 12a shows the 
effect of multiple disturbances on the water surface, with the result of 
interference patterns on the growing surface, the bright bands having a 
greater intensity than light passing through an undisturbed surface. FIG. 
12b shown the effect of a single disturbance on the water surface, again 
focusing light in bands on the bottom. 
Shading means 99 (FIG. 1) are also provided for shading a portion of the 
water surface for providing at least two sectors. A first floway sector 
992 is subject to available solar illumination, and a second floway sector 
994 is subject to shading. The different illumination levels impinging on 
the first 992 and the second 994 floway sectors are conducive for 
promoting different algal turf conditions therein, thereby providing 
different cleansing environments. 
Therefore, in use, water is admitted into the floway 2 by the inflow weir 3 
and is permitted to flow over the algal turf. The algal turf in the first 
sector 992 then serves as means for bioassimilating a first pollutant from 
the water to be treated, and the algal turf in the second sector 994 
serves as means for bioassimilating a second pollutant from the water to 
be treated, thereby cleansing the water of the first and the second 
pollutant. As previously, the water is then discharged from the ouflow 
weir 4 in a cleansed condition. 
A means for degrading volatile organic compounds (VOCs) is also provided, 
positioned, as shown in FIG. 1, adjacent an outflow weir 4. This means in 
a preferred embodiment comprises an ultraviolet reactor 98, shown in FIG. 
7. 
Water exiting from floway 2 flows into inflow manifold trough 982 and into 
the reactor body, which has sides 989 and a bottom sloping downward from 
the inflow trough 982 to the outflow trough 986. The water then flows 
across the bottom surface 984, which in the preferred embodiment comprises 
a textured and rippled TiO.sub.2 foil formed over fiberglass. Finally, the 
water flows into outflow trough 986, and empties out through the drains 
988. Supported above the flowing water between inflow 982 and outflow 
troughs 986 are ultraviolet lights 988 affixed beneath a sealed enclosure 
lamp hood 990. 
In an exemplary embodiment, reactor 98 has a width 981 between 1 and 40 ft, 
a length 983 between 4 and 50 ft, and a sidewall height 985 between 4 and 
60 in. Ripple heights 979 may be between 0.5 and 12 in., and the bottom 
slope 977 between 0.5 and 30%. 
In the foregoing description, certain terms have been used for brevity, 
clarity, and understanding, but no unnecessary limitations are to be 
implied therefrom beyond the requirements of the prior art, because such 
words are used for description purposes herein and are intended to be 
broadly construed. Moreover, the embodiments of the apparatus illustrated 
and described herein are by way of example, and the scope of the invention 
is not limited to the exact details of construction. 
Having now described the invention, the construction, the operation and use 
of the preferred embodiment thereof, and the advantageous new and useful 
results obtained thereby, the new and useful constructions, and reasonable 
mechanical equivalents thereof obvious to those skilled in the art, are 
set forth in the appended claims.