bluuebunny/crossref_metadata_2025 huggingface dataset:
Control of Activated Sludge Bulking: From the Lab to the Plant
Authors: Pujol R. , Boutin P.
Published: May 2018

Activated sludge bulking often occurs in French wastewater treatment plants. Precise identification of filaments and better knowledge of their ecophysiology helped to clarify their re1ations with the operational conditions of plants. Effective techniques were therefore developed for control. The “mixing zone” is suitable for many cases of bulking ocurring in extended aeration plants (the most common type in France). A test method was developed to provide the elements for dimensioning the system. Unreserved cooperation between the owner of the plant, the manager, the SATESE (Service of technical aid to wastewater treatment plant managers) and specialized laboratories is required to implement such measures. Some cases, about which CEMAGREF was consulted, were examined; three of them are detailed and reasons for success or fai1ure are analysed. Seeking funds for the works too often leads to excessive delays.
Urban Stormwater Reduction and Quality Improvement through the Use of Permeable Pavements
Authors: Pratt C. J. , Mantle J. D. G. , Schofield P. A.
Published: May 2018

Construction details are given of an experimental permeable pavement, comprising four separate sub-base sections containing different stone or crushed rock. Sub--base drain effluents have been monitored for discharge volume, flow rate and water quality parameters on the four sections. Preliminary results are presented which indicate that usefu1 volume and flow rate reductions may be obtained via permeable pavements, and that water quality may be enhanced by sedimentation and other treatment processes occurring within the pavement. Effluent quality may be improved as compared with that discharged from the usua1 impermeable highway surfaces in similar residentia1 areas.
Environmental Hazard of Eight Chemicals Present in the Rhine River
Authors: Halfon Efraim , Bruggemann Rainer
Published: May 2018

In this paper we rank the environmental hazard of eight chemicals, Disulfoton, Dinitroorthocresol, Propetamphos, Thiometon, Parathion, Etrimphos, Metoxuron and Fenitrothion found in the German section of the Rhine River. Five attributes related to the toxicity, physico-chemical characteristics and fate are used to rank the chemicals. Results by two ranking methods show that these chemicals can be divided into two groups, the most hazardous include Dinitroorthocresol, Propetamphos and Parathion, and the least hazardous include DisuHoton, Thiometon, Etrimphos, Metoxuron and Fenitrothion.
Experimental Studies on Biological and Chemical Oxidation of Dispersed Oil in Seawater
Authors: Literathy P. , Haider S. , Samhan O. , Morel G.
Published: May 2018

With an understanding of the different physical, chemical and biological weathering processes, a series of laboratory experiments were conducted to describe biological and chemical oxidation processes at realistically low concentrations of physically and chemically dispersed oil in seawater by incubating living and sterilized samples spiked with oil alone, oil-dispersant mixture and dispersant alone, under light and dark conditions. Biological oxygen demand and photosynthetic oxygen production were characterized by the variation in dissolved oxygen, whereas the degradation of oil and dispersant was followed by the variation in total extractable matter and surfactant concentration, respectively. Gas chromatography, infrared and fluorescence spectrophotometry were used for the characterization of the petroleum and its degradation compounds.

Biological oxidation was considered the major process in the living seawater sample incubated in the dark, and chemical oxidation, i.e., photo-oxidation, in the sterilized seawater sample exposed to light. In the early stages of each experiment, biodegradation of the physically dispersed oil progressed faster than the chemically dispersed one due to the concurrent degradation of the dispersant and the limited assimilative capacity of the seawater. The n-alkanes, mono- and dicyclic aromatic compounds showed significant biodegradation and limited photo-oxidation, whereas polycyclic aromatics were mainly photo-oxidized. Photo-oxidation was stimulated in the chemically dispersed oil. Synergistic degradation was observed when biological and chemical oxidation progressed simultaneously.
Relation Between Redox Potential and Oxygen Levels in Activated-Sludge Reactors
Authors: Heduit Alain , Thevenot Daniel R.
Published: May 2018

The importance of dissolved oxygen level in determining the platinum electrode potential in activated sludge has been clearly demonstrated by current-potential curves plotted at different oxygen concentrations.

Tests have been carried out, in the laboratory and in full scale treatment plants,to define the relationship between the platinum electrode potential at equilibrium (Eh) and the dissolved oxygen [O2] concentration in the activated sludge. These two parameters obey a law of the form Eh = a + b log [O2]. The measured values of coefficents a and b differ widely to those found from the oxygen reduction reaction in water (a = 0.8 V at pH 7 and b = 15 mV per decade).

Factors a and b mainly depend on the sludge loading, the aeration conditions and the sludge concentration. Using non–polished stationary platinum ring electrodes, the following values of a. were obtained (at pH between 7 and 7.6) : + 410 mV/NHE for sludge aerated for several hours without feeding, + 265 mV/NHE for over-aerated/low-loaded sludge (Cm = 0.2 kg BOD.kg MLVSS−1. day−1) and + 180 mV/NHE for high-loaded activated sludge in plug-flow system (Cm = 1 kg BOD.kg MLVSS−1.day −1). Factor b would seem to lie between 55 and 65 mV when the sludge is continuously aerated without feeding.At low loads with excess aeration, it lies between 70 and 90 mV. When the medium is slightly septic at low dissolved oxygen concentrations (insufficient daily aeration time, high sludge concentration or aerators shut down for too long periods), factor b increases and can reach 200 mV. In the same way, at high loads, factor b can become 150 mV.

These results demonstrate the importance of dissolved oxygen concentration in the mechanisms which determine the metal electrode potentials in activated sludge. They also illustrate the role that other electroactive species play in the process. The type and concentration of these species depend on parameters such as the sludge loading, the overall oxygen supply, the aeration sequence and the sludge concentration.
A Unified Method of Estimating Longitudinal Dispersion in Estuaries
Authors: Park J. K. , James A.
Published: May 2018

A procedure was developed to estimate the rate of longitudinal dispersion from the observed data and verified by applying it to both the narrow, partially-stratified estuary and the wide, well-mixed estuary. It was found that the dispersive flux is not proportional to the longitudinal salinity gradient (dS/dx) in estuaries and is most closely related to velocity, the advective flux and (dS/dx)2 rather than dS/dx. The results obtained from the procedure showed that negative longitudinal dispersion can occur especially in flood tide. It was investigated whether the dispersion coefficient estimated from observed salinity data can be applied to the prediction of a water quality, such as dissolved oxygen, BOD, ammonia or temperature. The observed dispersion coefficients were successfully applied in a water quality model.
An Optimization Study of the Planning of Water Pollution Control for Majiagou Stream in Harbin, China
Authors: Gong Yang , Peishi Qi , Baozhen Wang , Jun Sui
Published: May 2018

A study on the optimization planning of water pollution control for Majiagou Stream in Harbin was carried out. Four water pollution control options were considered. The option regarded as most feasible, both technically and economically, involved the construction and operation of a wastewater treatment works with a capacity of 150,000 m3/day on the upper reach of the stream. The effluent would be discharged into the upper reach of Majiagou Stream and would be used as a water source for the stream, while an interceptor sewer was to be constructed on the lower reach of the stream to collect wastewaters in the lower reach basin and transport them to a centralized wastewater treatment plant.

An optimization study of the relationship between the sewerage interceptor and the sewage treatment plant on the upper reach was conducted. In this study, a comprehensive water pollution control plan, including the sewerage system, sewage treatment plant, and the use of treated wastewater as a water source for Majiagou Stream, was considered as a systematic problem in which many factors were taken into account. Cost-benefit analysis was carried out for both the sewage treatment plant and the interceptors by means of empirical regression equations and diagrams in which various curves showed the relationships between the important factors.
The Development of Operator Training in the Republic of South Africa
Authors: Cormack R. H. , Lewis N. J. , Barnard J. J.
Published: May 2018

As part of the campaign to protect the Republic of South Africa's limited water resources, legislation has been drawn up stipulating the number and calibre of operators to be employed on a water care works. The registration and classification of both works and their operators will provide essential information for the refining and expansion of present training provisions.

Four new courses in water and wastewater treatment have been approved for inclusion in the National Technical Certificate system.

A preliminary training strategy is outlined and some anticipated improvements and modifications to be made in the years ahead are given.
Realising the Value of Research
Authors: Critchley R. F. , Anspoks V. P. , Greaves F. E. , Matthews M. G.
Published: May 2018

The aim of any research or development activity is to acquire benefit. There are many potential pitfalls preventing correct targeting of effort into the most beneficial areas or preventing full implementation of a proven idea. Some suggestions are presented, on the basis of practical experience in North West Water Authority, on how to achieve the value potentially available from a successful research investigation. In particular, the importance of active communication through reports, newsletters and seminars; stimulating demand through identifying key sites and carrying out on-site demonstrations; and providing adequate resources to enable take-up.
Measuring the Biological Effects of Pollution: The Mussel Watch Approach
Authors: Bayne B. L.
Published: May 2018

The Mussel Watch approach to environmental monitoring is briefly described and the potentials for various biological measurements to complement the normal practice of chemical determinations are discussed. Some of the available “biological effects techniques” are illustrated by reference to a recent practical workshop at which they were tested. Certain shortcomings in the approach are considered, but the conclusion reached that wider application of available biological techniques would benefit coastal environmental quality assessment.
Sewage Sludge Disposal: Current and Future Options
Authors: Bruce A. M. , Davis R. D.
Published: May 2018

Sewage sludge is an inevitable product of all conventional sewage treatment processes. Disposal of sludge in an economic and environmentally-acceptable manner is becoming generally more difficult. Sludge quantities are rising and disposal options decreasing. Disposal will increasingly require positive and careful management. There are four basic destinations for sludge - agriculture, other types of land, the sea or minor outlets. Treatment methods are available for the production of nine basic types of end-product to suit particular disposal requirements. The new EC Directive will regulate sludge to agriculture and will require that all sludge to farmland is treated unless it is immediately buried under the soil.

Sludge to agriculture (grassland or arable) is subject to soil metal limits and to the need to minimise the risk of disease transmission. Sludge to landfill is subject to increasing constraints, particularly on physical stability. Sludge to sea is still practised by the UK but is closely controlled by Government licence and a requirement for monitoring. Minor outlets such as oil production, protein extraction etc are only at the experimental level. A computer program (WISDOM) provides a means of evaluating the short/long-term viability of alternative treatment and disposal options to identify the most economic and environmentally-acceptable strategy on an objective basis.
Simultaneous DO Control and Respiration Estimation
Authors: Holmberg Ulf , Olsson Gustaf , Andersson Bengt
Published: May 2018

The oxygen uptake rate (or respiration) is a crucial variable in the operation of an activated sludge plant. A method has been developed and tried in full scale to estimate the respirat ion while controlling the dissolved oxygen. The strategy allows a simultaneous tracking of the respiration rate and the oxygen transfer rate. This has not been possible to do in earlier methods. The control strategy is dual in the sense that the control signal, the air flow rate, is used both to control the DO concentration and to excite the DO dynamics sufficiently to allow the parameters to be estimated. The excitation is introduced automatically by a relay feedback resulting in an oscillation of the DO around its set point. Tuning of the relay gain makes then a nice compromise between fast tracking and accurate control. The dual controller and estimator has been tested during a limited series of experiments in full scale at the Malmö Sewage works in Sweden.
Automation of Batch Wastewater Treatment Systems Using Programmable Logic Controllers
Authors: Alleman James E. , Sweeney Michael W. , Kamber Dennis M.
Published: May 2018

Total automated process control of a full-scale wastewater treatment facility was successfully achieved using a programmable logic controller. This facility includes three (3) sequencing batch reactors, three (3) downflow pressure filters, and two (2) ultraviolet disinfection units. The control system routinely manipulates 68 equipment items within the plant, as well as continuously monitoring the operational status of all such equipment. The controller also handles emergency startup/shutdown conditions, cycling of redundant equipment items, and equipment failure situations. In addition, telephone→modem communication with the controller can be obtained to facilitate remote system evaluation and troubleshooting. National recognition of the engineering design excellence and innovation applied to this unique automated facility was recently awarded by the American Consulting Engineers Council, with its designation of this plant as one of the top ten engineering projects within the United States for 1986.
Instrument Triplication in Sewage Treatment
Authors: Burns J. M.
Published: May 2018

One of the main problems with the introduction of automation is the poor performance of same instrumentation. One possible way of improving this situation is through triplication of the instruments (that is the use of triple active redundancy). This approach should give improvements in data availability, accuracy and help identify instrument faults. Reliability theory may be used to show that gains in availability of up to 10% are possible, but if the basic instrument availability is less than 50%, then triplication will actually decrease the overall availability. The dissolved oxygen instruments at Witney STW (Thames Water) have been triplicated. Individual instruments were found to have an availability of 90% giving a theoretical triple availability of 97%. The overall availability measured was only 92%, mainly because the failures were not always random and independent. Uncertainty in the data was reduced by 40% because of the effect of averaging but drift detection was not as successful as hoped due to the presence of significant short term jitter in the DO readings. The cost of triplication can be significant in both extra hardware and extra maintenance. In the light of these points some comparisons are made with other methods of improving reliability.
Control of Polymer Addition for Sludge Conditioning: A Demonstration Study
Authors: Campbell H. W. , Crescuolo P. J.
Published: May 2018

The need for automatic control of sludge conditioning systems resulted in the development of the sludge conditioning controller (SCC). The fundamental concept behind the SCC and the development of the commercial prototype are described in the paper. The final phase of the program involved demonstrating the operation of the SCC at a full-scale dewatering plant. The SCC was installed on a two metre belt press, dewatering anaerobically digested sludge. The evaluation was conducted by comparing the results of historical manual operation with those achieved on the same press under automatic SCC control. Analysis of the data indicated that an average 24% polymer saving could be achieved by the automated system. The paper also describes the practical problems that were encountered during the installation of the control system.
Automation and Optimisation of Centrifuge Sludge Dewatering
Authors: Schrank Gunter , Murren Clive
Published: May 2018

The dehydration of sewage treatment plant sludges has become one of the major problems in the treatment of waste Water. Very high costs, especially those of flocculation additives, increasingly call for optimisation of this phase of the process. Taking the dewatering of sludge by centrifugation as an example, two different approaches can be considered: mechanical excess sludge thickening without the use of additives and the dehydration of sewage sludge with use of chemical additives. A prerequisite of any automation is the reliable acquisition of data of the parameters required for control. Continuous measurement of the concentration of suspended solids in the sludge that is to be dewatered, of sludge flow and of the turbidity of the clear phase (centrate) leaving the centrifuge, make it possible to design several methods of effective control.
Optimisation of Aeration Efficiency: A Design Procedure for Secondary Treatment Using a Hybrid Aeration System
Authors: Thomas V. K. , Chambers B. , Dunn W.
Published: May 2018

The fine-bubble diffused air (FBDA) system of aeration is most efficiently operated in low rate activated sludge systems. The aeration technique is, however, subject to poor oxygen transfer efficiency and diffuser clogging under increased loading conditions such as are experienced close to the tank inlet in plug-flow systems. Mechanical, surface aeration systems, though apparently less efficient, do not suffer from these disadvantages. The ideal aeration tank configuration, for optimum aeration efficiency is therefore:–inlet anoxic zone–completely mixed surface aerated zone–plug-flow, fine-bubble diffused air zone with tapered aeration–clarification tanks.

An overall aeration efficiency of 1.5-2.0 kg/kwh is predicted for nitrifying systems, together with an increased diffuser lifetime compared to a conventional FBDA tank. The design procedure is illustrated using parameters for a large UK works. Despite greater civil costs, the reduced running costs and NPC of the hybrid system make it an attractive option when compared to a plug-flow FBDA system or a conventional surface aeration plant.
Sewage Sludge Disposal in Southern California, U.S.A.
Authors: Garber William F.
Published: May 2018

Disposal of sewage solids resulting from wastewater treatment processes has historically been the most difficult and “unsolved” problem in the handling of water-carried wastes in Southern California. Continuing rapid growth combined with Federal laws which essentially prohibit any discharge of sludge to the ocean regardless of net effects upon the land) water and air total environment have exacerbated this problem to an almost critical state. Complex incineration processes directed at producing energy from dried sludge while minimizing negative atmospheric impacts are under construction. Their complexity has resulted in start-up problems related to the short time allowed for design and break-in by Federal Court action. Increased sludge disposal amounts are also resulting from Federal insistence upon full secondary treatment prior to ocean disposal regardless of net environmental impact. Four large facilities were examined: the Sanitation Districts of Los Angeles and Orange Counties, the City of San Diego and the City of Los Angeles. Differing approaches to disposal have been chosen with landfills receiving most sludge at the present and incineration planned for most in the future. Description of the current practices with the amounts of solids to be disposed of and the current costs are outlined.
Recent Advances in Mechanical Dewatering of Digested Sludge
Authors: Knight Earl W.
Published: May 2018

The present sludge processing operations at the District consist of heated anaerobic digestion, dewatering by centrifugation, and air drying. A critical unit operation in the overall sludge processing train is the mechanical dewatering step. Typically, sludge dewatering by the District's existing centrifuges produces a cake having a solids content of 15%. Four different types of mechanical sludge dewatering machines were evaluated in a pilot test program to determine if these machines could produce cakes having greater solids contents than that produced from the existing centrifuges. The machines tested were two modified versions of the conventional horizontal solid bowl centrifuge design, a screw press, and a diaphragm filter press. The two modified centrifuges produced cakes having average solids contents of 20% and 29.4%, respectively; the screw press produced a cake having an average solids content of 17.5%, and the diaphragm filter press produced a cake having an average solids content of 29.4%. Based on the pilot test program, a test evaluation program was conducted using full-scale centrifuge machines of the modified designs. The preliminary results of this test program confirmed that centrifuges can produce a cake with a solids content approximately equal to or greater than 30%.
Full-Scale Experience with Sludge Treatment at the Vienna Sewage Works
Authors: Thomas Ruggenthaler Peter
Published: May 2018

The sewage treatment plant at Simmering, Vienna, has been operating since June 1980, together with the ‘EbS' plant for sludge treatment and disposal. This latter consisted of centrifuges, grinder dryers and fluidised bed incineration but due to difficulties with the grinder dryers it has never operated efficiently. Accordingly trials have been done using improved centrifuges and filter presses to increase the dry solids content of the cake fed to the incinerators without using the grinder dryers. It was found that all systems tried were an improvement on the existing but that the best result was achieved using a Centripress on preheated sludge conditioned by polyelectrolyte. The plant was converted to this system in 1987 and results of full-scale operation as well as test results are given in the paper.
Conversion of Sludge to Oil: A Novel Approach to Sludge Management
Authors: Campbell H. W. , Bridle T. R.
Published: May 2018

Experiments at the Wastewater Technology Centre have shown that low temperature conversion of sludge to oil represents a promising alternative to sludge incineration. A 1kg/h bench-scale reactor produced oil yields ranging from a low of 13% for an anaerobically digested sludge to a high of 46% for a mixed raw sludge. Char yields ranged from 40 to 73% at the optimum operating temperatures. Preliminary results from a 40 kg/h pilot plant were similar to those obtained on the bench-scale system with the same sludges. The economics of the conversion process are compared with those for incineration. The impact of the “sludge to oil” technology on the design of sludge management systems is also discussed.
Phosphatase Activity of Water as a Monitoring Parameter
Authors: Matavulj M. , Bokorov M. , Gajin S. , Gantar M. , Stojilković S. , Flint K. P.
Published: May 2018

The biological monitoring of water saprobity and trophic degree primarily involves the study of qualitative and quantitative composition of organisms present in the water. Although relatively satisfactory as an indicator of the water's organic load, the counting of bacteria is often an unreliable parameter. Due to their polyenzymatic nature, which enables flexible adaptation to new and different physico-chemical conditions of their habitats, microorganisms respond quickly to trophic degree change, but faster by changing the level of their enzyme activity, than by changing the number of cells. On the basis of these findings, the enzyme activity of microbialaquatic biotopepopulations is suggested in recent literature as an additional indicator of the degree of organic load in the water.

The results obtained by investigation of the phosphatase activity in samples from natural and artificial water accumulations and flowing waters in Vojvodina Province, having different eutrophic degree, suggest the measurement of the level of water enzyme activity as an additional biochemical indicator of saprobity degree. At the same time, on the basis of long--term measurement of the water phosphatase activity, compared to classical categorizations based on qualitative and quantitative composition of organisms present in the water, classification of surface freshwater s into quality categories according to the level of enzyme (phosphatase) activity of water is proposed.
Content of Heavy Metals in Some Fish Species in the Section of the Danube Flowing through Vojvodina
Authors: Pujin V. , Djukic N. , Maletin S. , Obradovic S. , Kostić D.
Published: May 2018

The content of 11 heavy metals (Al, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, Sr, Zn) was analysed in certain tissues and organs in 12 fish species in the river Danube, Vojvodina (Yugoslavia). The studied selectivity of accumulation of heavy metals varies in these fish species. Most of the heavy metals were deposited in higher concentrations in the intestines than in the muscles. However, this ratio was just the opposite in piscivores.
Nutrient Input and Trophic Status of the “Neue Donau”, a High-Water Control System along the River Danube in Vienna, Austria
Authors: Dokulil M. T. , Janauer G. A.
Published: May 2018

The system “Neue Donau” functions as a control system for high waters of the river Danube and is an important recreational area for many people. Water quality and trophic status of the water body is thereforeof prime importance. The high nutrient concentrations of the river Danube (P-tot 238±41µg/l, N-tot 2.53±0.78 mg/l) reach the system via groundwater seepage. Present conditions in the basin of Neue Donau are,as a result of this nutrient in-flux,eutrophic to hypertrophic. Average values during the summer period have declined from 366 µg/l total phosphorus to 78 µg/l, and from 86 µg/l chlorophyll-a tol7µg/l between the years 1985 and 1988. However, a dam which is planned in the river at Vienna will permanently raise the water level of the river thus increasing the the groundwater flow in the direction to the Neue Donau and therefore the nutrient input which will enhance trophic conditions in the impoundment. Since macrophytes play an important role in one part of the system macrophyte management together with measures along the river are some of the suggested strategies to keep the system Neue Donau at acceptable trophic conditions and good water quality.
Effects of Warm Wastewaters from Thermal Power Stations on Ecosystems of the Sava and the Velika Morava, Tributaries of the Danube
Authors: Janković D. V.
Published: May 2018

Investigations were conducted over several years, from 1977 to 1989, into the effects of warm wastewaters from thermal power stations on ecosystems of the Sava and the Velika Morava, tributaries of the Danube in Yugoslavia. The thermal power stations (TPSs) were the ‘Morava' TPS, situated near Svilajnac on the River Morava, and ‘Nikola Tesla A and B' TPSs near Obrenovac on the River Sava. These rivers also receive industrial and urban wastewaters along their whole length. The temperature differences between the river waters abstracted and the wastewaters returned to the rivers were from 8 to 15°C. In the areas influenced by these warm wastewaters, greater heterogeneity of ichthyofauna and faster growth and maturation of fish were observed. These were considered to be positive effects. Due to the periodic washing out of TPS coal ash repositories which are located in the riparian areas, concentrations of sulphates, phosphates, and nitrates have been increasing in the Morava, which may have negative effects on the aquatic communities. High ambient temperatures in the summer, during periods of low water and reduced oxygen content in the polluted river conditions, also had negative influences on the water ecosystems. The warm wastewaters from the thermal power stations could be used in aquaculture, which would decrease the thermal pollution of the rivers during summer lower water periods.
Risk Management of Accidental Water Pollution: An Illustrative Application
Authors: Pintér J. , Benedek P. , Darázs A.
Published: May 2018

A general risk assessment and management approach is proposed for analyzing and controlling (accidental) environmental pollution events. This concept is illustrated by a simplified case study, describing hypothetic point-source toxic pollution of the river Danube and its effect on the downstream bank-filtered well system. The numerical example indicates the viability of the suggested approach, highlighting also the necessary information base of environmental risk studies.
Assessment of the Potential for in Situ Biotreatment of Hydrocarbon-Contaminated Soils
Authors: Morgan Philip , Watkinson Robert J.
Published: May 2018

Enhanced insitu biotreatment is a recent technology for the cleanup of contaminated soil and ground water but it has not yet been tested for many contaminants. This report describes the assessment of three hydrocarbon-contaminated sites, one contaminated with crude oil, one with lubricating oil and one with gasoline, with respect to their potential for biotreatment. All locations were permeable, sandy soils which contained low concentrations of extractable inorganic macronutrients. Degradative microbial populations were present, although their numbers were reduced in the most highly contaminated portions of the soil. Hydrocarbon analysis demonstrated that vertical penetration of contaminants into the soil was poor for the crude oil but had occurred at the other sites. There was some evidence that biodegradation at the crude and lubricating oil-contaminated sites may have occurred. The available data suggested that biotreatment of the lubricating and gasoline-contaminated sites by the provision of inorganic nutrients and oxygen to the soils might prove viable. However, it was found that the addition of inorganic nutrients resulted in an inhibition of mineralisation in the soils.
Behavior of Aquifers Concerning Contaminants: Differential Permeability and Importance of the Different Purification Processes
Authors: Gibert J.
Published: May 2018

Contaminants in transit through groundwater systems cross different types of rocks, each one with different water-bearing characteristics. It is imperative to understand the behavior of different aquifers (porous or karstic) concerning contaminants and the relative functions and mechanisms of major processes in a given system before planning remedial measures. From the surface systems to groundwater four main types of filter can be considered. They intervene most often simultaneously and the interactions are very strong. The activities of the different filters lead us to the concept of permeability, which varies according to the efficiency of the filter, ranging from the most impermeable porous aquifers to karstic aquifers. Among major processes we have chosen to consider three groups: retention, selfpurification and dilution and to discuss their importance and their rate of change. We focus more specifically on the problem in karstic systems. An example concerning nitrate profiles in a French karstic system is given, showing an increase of nitrate concentration in the epikarstic zone due to the impact of agriculture. Very few studies on karstic system contamination are mentioned because the processes controlling contaminant cycling inside the karst are as yet not very well understood.
Coagulation as Pretreatment of Food Industry Wastewater
Authors: Rusten B. , Eikebrokk B. , Thorvaldsen G.
Published: May 2018

Jar-tests, pilot-plant and full-scale experiments on chemical pretreatment of food industry wastewater have been performed. The objectives were to find maximum removal efficiencies, suitable coagulation and flocculation agents, and the optimum process design. The results showed that the wastewater composition greatly influences the maximum removal efficiencies and also the conditions for optimum coagulation and flocculation. Optimum pH depends on the chemical agent and the actual dosage used. With proper pH-adjustment, addition of either 0.10-0.15 mg FeCl3-6H2O/mg COD, or about 0.20 mg Al2(SO4)3.18H2O/mg COD, was sufficient to obtain good removal of organic matter. Maximum removal efficiencies of 67-90 % total COD were achieved, depending on wastewater composition.
Pretreatment of Poultry Processing Wastewater in a Pilot-Scale Anaerobic Filter
Authors: Harper S. R. , Ross C. C. , Valentine G. E. , Pohland F. G.
Published: May 2018

Wastewater from a typical poultry processing plant in the southeastern U.S.A. was treated on site with a pilot-scale anaerobic packed-bed reactor. The reactor had a working volume of 3.2 m3, was filled with 15-cm diameter polyethylene random-pack media, and was operated at 35°C with a retention time of 21 hours and at a loading rate of 2.8 kgCOD/m3d−1. Under these conditions, treatment efficiencies were sufficient to meet typical surcharge-free municipal discharge requirements, with effluent soluble COD of 440 mg/L, soluble BOD5 of 190 mg/L, fats, oil and grease (FOG) of 10 mg/L, and total suspended solids of 140 mg/L. Results from pilot operation are compared to those of previous laboratory-scale studies, where similar results were obtained with less than half of the hydraulic retention time. Differences in treatment on pilot vs. laboratory scale were largely due to differences in wastewater variability and reactor operation. Recommendations for future studies to reduce the costs of treatment, including emphasis on types of low-cost packing, amounts of packing media, and heating requirements are presented.
Pretreatment of Textile Processing Wastewaters
Authors: Tünay O. , Tameroǧlu O. , Baykal N. , Afşarünal F. , Ödemiş E.
Published: May 2018

In this paper, the pretreatment approaches in the textile processing industry are discussed and two case studies which have been carried out in two textile processing plants are delineated. Case studies include the phases of process and pollution profiles, treatability study, conceptual design and evaluation of one-year actual treatment plant performances. One of the treatment schemes applied was chemical coagulation while the other was activated sludge. Therefore a comparison of two main types of pretreatment has been realised. Results indicate that biological treatment is more efficient and reliable in terms of organic matter removal as compared to chemical coagulation. Comparisons of cost of initial investment, cost and ease of operation, and sludge production are also made and discussed.
The Stratified Facultative Lagoon for the Treatment and Storage of High Strength Agricultural Wastewaters
Authors: Schulz T. J. , Barnes D.
Published: May 2018

A research and development programme at The University of New South Wales and a large intensive piggery located on the outskirts of Sydney, Australia, has culminated in the successful commissioning of an odour control process for the storage and treatment of wastewaters from the piggery. The stratified facultative lagoon utilises surface aeration of an otherwise anaerobic lagoon to provide a non-odorous cover for the anaerobic contents. The process has filled a need in the pig industry for a non-odorous cost effective alternative to conventional treatment systems, prior to wastewater re-use or disposal by land application. Critical design parameters include lagoon depth, specific energy input and aeration system design. Mean removal efficiencies of biochemical oxygen demand of 75 per cent have been achieved consistently. The development of the process was facilitated by the use of wastewater redox potential testing to indicate the likely presence of odorous compounds in the liquid on the surface of the lagoon and in the surrounding atmosphere. Surface redox potential readings (Eh) greater than −76 mV resulted in non-odorous operation of the process.
New Process for Physico-Chemical Pretreatment of Dairy Effluents with Agricultural Use of Sludge Produced
Authors: Kárpáti Á , Bencze L. , Borszéki J.
Published: May 2018

A combined physico-chemical process is suitable for the effective pretreatment of dairy effluents, achieving almost complete removal of fat, and considerable reduction of protein content. The specific cost of COD removal using the process is only half or a third of that using aerobic biological methods. Depending on the chemicals used, further treatment or, in certain cases, agricultural utilization, of the sludge is possible. In addition, the components remaining in the effluent have low molecular weights, are easily degradable, and are very favourable as nutrients in municipal aerobic post-treatment. Investigation of the sludge showed that it did not contain any pathogen organisms and therefore its application on land is recommended. Laboratory and field experiments have shown that, with agricultural use of the sludge, increased plant growth and grain production were achieved.
Successful Dewatering Experience at Hyperion Wastewater Treatment Plant
Authors: Horenstein Bennett K. , Hernandez Gerald L. , Rasberry Gary , Crosse John
Published: May 2018

The City of Los Angeles has developed a diversified sludge management program since cessation of the ocean disposal of sludge in November 1987. At the heart of this program is the centrifugal dewatering of digested sludge at the Hyperion Wastewater Treatment Plant. The experience gained from the dewatering process includes: centrifuge startup problem solving, optimization of the dewatering process, polymer testing, struvite monitoring and control, and waste activated sludge dewatering parameter development.
Oxygen Utilization Rate as a Control Parameter for the Aerobic Stage in Dual Digestion
Authors: Messenger J. R. , de Villiers H. A. , Ekama G. A.
Published: May 2018

From a study of the performance of the autothermal thermophilic aerobic stage (45 m3) of a full-scale dual digestion plant, operated with pure oxygen, it was found that: (1) VS and/or COD removal are poor parameters for estimating biological heat generation; (2) the biological heat generation is proportional to oxygen utilized at 13.0 MJ/kgO, a value which conforms closely to that obtained from bioenergetics and thermodynamics, (3) the maximum biological heat generation rate was limited by the maximum oxygen utilization rate of the sludge (OURbio), and (4) because the aerobic reactor is oxygen limited, the temperature could be completely and instantaneously controlled with oxygen feed rate up to OURbio; (5) CO2 generation in the vent gas was 0.68 mol CO2/mol O2 utilized instead of 1.0 usually assumed.
Studies on Microbial Leaching of Heavy Metals from Municipal Sludge
Authors: Tyagi R. D. , Couillard D. , Tran F. T.
Published: May 2018

A comparative study between continuous stirred tank reactor (CSTR) with cell recycle and air-lift reactor was carried out in 30 1 capacity reactors for metal solubilization from anaerobically digested sludge. In CSTR at a residence time of 0.75 day, supplementing the feed sludge with 4 g/l of FeSO4.7H2O, using 20% sludge recycle and adjusting pH of the feed sludge to 4.5 resulted in following metal solubilization : 91% Cu, 94% Zn,, 93% Mn, 67% Cd, 67% Ni, 8% Cr, and 7% Pb. At 0.75 day retention time metals were solubilized to the recommended level in CSTR as well as in air-lift reactor. The treated sludge is easy to filter in plates filter press, centrifugation, or vacuum filter. The sludge nutrients do not seem to be diminished as a result of treatment and separation of solid-liquid. The ammonia-nitrogen fraction seems to be transformed in organic nitrogen. The decontaminated sludge produced has less odour.
Physical Chemistry of the Interface between Attached Micro-Organisms and Their Support
Authors: Rouxhet P. G. , Mozes N.
Published: May 2018

The thermodynamic approach of adhesion and DLVO theory are complementary to predict initial bacterial adhesion; the interplay between short- and long-range forces, respectively, may be due to surface roughness. Due to the influence of electrical double layer interactions, adhesion can be promoted by treatments leading to modification of the cell or support surface properties. Adhesion is influenced by cell-cell interactions, by the cpresence of polymer molecules on the surface and by the composition of the medium.

X-ray photoelectron spectroscopy can be applied to determine the elemental composition of the surface of microorganisms; some information on the chemical functions can also be obtained. The surface composition is related to physico-chemical properties which play a determining role in adhesion and flocculation, in particular the hydrophobicity and the zeta potential.
Biomass Retention in Advanced Anaerobic Reactors
Authors: Albagnac G.
Published: May 2018

Recognition of the advantages of anaerobic wastewater treatment induced the development of high rate processes, i.e. reactors designed to allow an efficient treatment of even diluted streams. The performance of these advanced reactors is mainly dependent on the retention within the reactor of high bacterial concentrations. The prevailing mechanism is either the formation of bacterial aggregates with good settling characteristics, the development of methanogenic biolayers at the surface of inert carriers or both.

During the past decade information on the biology of methanogenic ecosystems became available at an increasing rate. From a practical point of view it can be stated that the biological conversion of organic compounds to methane is reasonably well understood. However the current knowledge on the aggregation and adhesion of methanogenic consortia remains very limited. In most cases reactor start-up procedures are rather long and appear to be more empirical than rational.

This paper is a brief presentation on the current knowledge of methanogenic aggregates and biofilms. The fundamental aspects of bacterial adhesion and the modelling of anaerobic biofilms growth are presented elsewhere.
Rule of Thumb Modelling of Biofilm Reactors
Authors: Elmaleh S.
Published: May 2018

Biofilm reactors are very complex systems, the modelling of which requires sophisticated kinetic relationships concerning the highest number of species in reaction and computer simulation. In fact, the process engineer needs a rule of thumb method able to predict the output variables after modification of the operational variables. Such a “simplissime” model is derived by considering a plate reactor coated with a biofilm through which the substrates are diffusion transported and eliminated with a zero order intrinsic reaction. When the liquid-biofilm resistance is neglected, conversion depends on one parameter only, the meaning of which can be displayed. Moreover, in many cases, the flow pattern influence can be neglected. This “simplissime” model was shown accurate enough in fitting various experimental data and it can even be used as a design tool.
Danish Experience with Emergent Hydrophyte Treatment Systems (EHTS) and Prospects in the Light of Future Requirements on Outlet Water Quality
Authors: Schierup H.-H. , Brix H.
Published: May 2018

Since 1983 approximately 150 full-scale emergent hydrophyte based wastewater treatment plants (reed beds) have been constructed in Denmark to serve small wastewater producers. The development of purification performance for 21 plants representing different soil types, vegetation, and hydraulic loading rates has been recorded. Cleaning efficiencies were typically in the range of 60-80% reduction for BOD, 25-50% reduction for total nitrogen, and 20-40% reduction for total phosphorus. The mean effluent BOD, total nitrogen and total phosphorus concentrations of the reed beds were 19 ± 10, 22 ± 9 and 6.7 ± 3.2 mg/l (mean ± SD), respectively. Thus, the general Danish effluent standards of 8 mg/l for N and 1.5 mg/l for P for sewage plants greater than 5,000 PE cannot be met by the present realised design of EHTS. The main problem observed in most systems is a poor development of horizontal hydraulic conductivity in the soil which results in surface run-off.

Since the political demands for effluent quality will be more strict in the future, it is important to improve the performance of small decentral sewage treatment plants. On the basis of experiences from different types of macrophyte based and conventional low-technology wastewater treatment systems, a multi-stage system is suggested, consisting of sedimentation and sand filtration facilities followed by basins planted with emergent and submergent species of macrophytes and algal ponds.
Technology Assessment of Wastewater Treatment by Soil Infiltration Systems
Authors: Jenssen P. D. , Siegrist R. L.
Published: May 2018

Infiltration of wastewater in buried soil infiltration systems has been promoted as a low cost, effective alternative for treatment and disposal of wastewater flows from commercial developments and small communities. Unlike many mechanical wastewater treatment systems, soil infiltration systems are subject to complex, far-reaching influences related to natural site conditions and the interaction of wastewater with a dynamic soil and ground water system. As a result, design and performance relationships are not always well defined and systems are often implemented based on local tradition and empiricism. Consequently there is a need for improvement of design criteria especially for large subsurface wastewater treatment systems.

Successful performance starts with thorough site investigations, where large scale infiltration tests or tracer studies might be needed. The hydraulic loading rate is a principal design parameter. An integrated approach for assessment of the hydraulic loading rate based on soil type and wastewater quality is suggested. In general, trench design should be preferred over beds, but rational criteria for selection of optimal geometry is lacking. Purification performance of subsurface wastewater infiltration systems is generally good. Estimates of purification on the basis of soil grain size, soil depth and loading rate can be given.
Modification of Small Activated Sludge Plants to Recycled Systems for Nitrogen Removal and Control of Settling Properties
Authors: Brenner Asher
Published: May 2018

Modification of small activated sludge plants to recycled systems is proposed as a means to improve nitrogen removal and control of settling properties. The modification process involves separation of the aeration basin to anoxic and aerobic zones and addition of internal recycle of mixed liquor from the aerobic to the anoxic zone. This mode of operation may prevent problems of floating sludge in the final clarifier caused by uncontrolled denitrification. In the recycled system, part of the organic carbon is removed under anoxic conditions. Therefore, it may assist in the selection of microbial population with better settling characteristics, since most filamentous microbes have been reported to lack denitrifying ability. The modification considerations and guidelines are discussed based on experimental results obtained from operation of bench-scale recycled units. Influent COD/ammonia ratio, aerobic volume fraction, and recycle rate are shown to be critical parameters in the modification and operation of such systems.