bluuebunny/crossref_metadata_2025 huggingface dataset:
Developments in Laboratory Evaluation of Sewage Sludges Dewaterability
Authors: Lotito V. , Mininni G. , Spinosa L. , Lore F.
Published: May 2018

Literature review shows that particle size distribution, water distribution and rbeological properties can play an important role in the evaluation of dewatering performance. Following a previous study on relationships between Theological parameters and filterability parameters, work has been addressed to the understanding of the influence of particle size and water distribution on specific resistance to filtration.

Tests were carried out on different types of sludge (raw, digested, conditioned). Two substantially different techniques for measuring the particle size distribution were used, showing that the mechanical technique (sieving) resulted in larger particle sizes than the optical (laser diffraction). Results showed that particle size distributions play a role in describing sludge filterability.
Progress in Characterization of Sludge Particles
Authors: Friedrich E. , Friedrich H. , Heinze W. , Jobst K. , Richter H.-J. , Hermel W.
Published: May 2018

The studies aimed at examining the influences of the particle size distribution and surface charge on the behaviour of sludge in dewatering. It was possible to show that defined size dispersions of sludge particles as well as surface charge are necessary to reach better dewatering results and that the found correlations were independent of the type of sludge and the sewage treatment plant (Friedrich et al., 1990 and 1991). Based on laser diffraction measurements to determine panicle size distribution it was found that it was necessary to set a specific proportion between fine and large sludge particles in order to produce the best possible dewatering results and to get the required shear resistant flocs. To characterize the surface charge of the sludge particles various measuring methods were used. Determining the zeta-potential is a suitable means to describe the kinetics of degradation process in the sludge.
Whey Disposal: Recovery of Nutrients for Animal Feeding
Authors: Guirguis N. , Brosnahan C. , Hickey M. W.
Published: May 2018

It has been estimated that over 50% of whey production world wide constitutes a pollution problem to the environment. A proportion of the work carried out to make use of whey nutrients has not been commercially viable. A simple process has been developed, at the laboratory and pilot plant scales, resulting in a complete recovery of nutrients from whole whey or whey fractions for animal feeding and no further waste or effluent is generated. The economics of the proposed process rely on efficient use of inexpensive ingredients (or waste materials, from other agricultural sources) to overcome the high cost of dewatering and drying.

Using this approach a number of products are possible. In the first product bentonite is used to precipitate whey protein which can be processed into a dry protein concentrate for use in intensive animal, poultry or fish production. This product compares favourably with conventional protein supplements such as meat and bone, soybean, or fish meal. The deproteinised whey, (mainly lactose and minerals) arising from this process, is concentrated and mixed with a carrier to produce a second product for ruminants that can compete with hay or grains. Further, whole whey may be used in a similar process.

Animal feeding trials with sheep and dairy cattle have demonstrated advantages of the developed whey products over conventional feed supplements for wool growth, live sheep export or milk production.
Feasibility of Anaerobic Sewage Treatment in Sanitation Strategies in Developing Countries
Authors: Alaerts G. J. , Veenstra S. , Bentvelsen M. , van Duijl L. A.
Published: May 2018

Sanitation strategies in the growing cities may aim at protection of shallow groundwater, public health protection, removal of oxygen-consuming substances andre moval of nutrients. It is shown that anaerobic treatment of municipal waste waterin UASB type reactors has become afeasible treatmentoption in those strategies. This study investigates the merits of the technology for on-site management of black and grey waste water, and for off-site centralised treatment. At on-site scale where effluent is leached into the ground, anaerobic reactors offer no advantage over cheaper leaching pits. At larger centralised scale, anaerobic reactors have performed well and reliably over longer periods. Post-treatment may be required, but the total treatment is financially advantageous in warm climates; if land cost is low long-retention ponds may be more attractive, however. In addition, the technology's characteristics open the possibility to develop “intermediate” solutions at township-level based on low-cost (shallow and small-bore) sewerage and reactors for communities of typically 100 up to 1000 households. Sludge, produced in lower quantity, dries easily. Pathogen removal is limited, and biogas production only a minor asset.
Treatment of a Domestic Wastewater with UASB Reactors
Authors: Gnanadipathy A. , Polprasert C.
Published: May 2018

This study investigated a feasibility of employing pilot-scale upflow anaerobic sludge blanket (UASB) reactors to treat a domestic (or relatively low-strength) wastewater. Four 30-1 UASB reactors, each with a 0.15-m inner diameter and 2-m height were used in this study which was conducted at an average ambient temperature of 30°C. Three reactors were inoculated with different types of seed sludge, namely: sludge from a facultative waste stabilization pond, anaerobically digested sludge and sludge from a UASB reactor treating a distillery wastewater. The fourth reactor was started without inoculum and was studied for possible self inoculation. Domestic wastewater was mixed with a stock glucose solution to increase the influent COD concentrations to about 600 mg/l. All four reactors were started with a hydraulic retention time (HRT) of 24 h, and this HRT was later reduced to 12, 6 and 3 h, consecutively, corresponding to the organic loading rates (OLR) of 0.4-0.6, 0.9-1.4, 1.8-2.8 and 3.6-6.0 kg COD/(m3.d), respectively.

At the highest OLR or shortest HRT, there was about 90% removal of the influent COD in Reactors 1-3 while the methane (CH4) production rate was found to be 150 N1/kg COD removed with a methane (CH4) content of 75%. Reactor 4, without inoculation, could not develop sufficient amount of biomass to withstand the high OLR and its performance deteriorated at the HRT of 3 and 6h. The scanning electron microscopic (SEM) examinations of the sludge floc revealed the predominance of Methanothrix-like bacteria in all reactors. The experimental results obtained have suggested a technical feasibility of employing UASB reactors to treat domestic wastewaters. The facultative waste stabilization pond sludge and anaerobically digested sludge were found to be suitable inoculum sources for the UASB reactors treating this low-strength wastewater.
Dewatering Characteristics of Oily Sludge
Authors: Tay Joo-Hwa , Jeyaseelan S.
Published: May 2018

Proper sludge conditioning facilitates better dewatering of sludges. Sludge conditioning techniques required for different sludges bigbly depend on the properties of the sludges. Dewatering characteristics of oily sludges were studied for different degrees of oil content in sludge with lime as sludge conditioner. The optimum dosage of lime was found to range from 6% to 10% to yield favourable characteristics of the sludge for better filterability. Also the established correlations between the combinations of dewatering characteristics, such as specific resistance, capillary suction time, cake solid content and filter yield provide means of quick indication for the nature of the sludges.
Elimination of Nitrogen and Phosphorus from Sludge Liquor
Authors: Wedi D. , König E.
Published: May 2018

Sludge handling and dewatering results in an additional load on biological wastewater treatment. Especially for the process of biological phosphorus removal, high phosphorus release during anaerobic sludge treatment is expected. In this study the reduction of phosphorus and nitrogen load from sludge liquor in different pilot scale tests was performed. The processes examined here are P-precipitation with salts of aluminium and iron, as well as pH-controlled precipitation with lime. For nitrogen removal this process can be extended to air stripping at high pH-values. The combined MAP (magnesia-ammonia-phosphate)-precipitation of ammonia and phosphorus was subject of the study, too. At proper applications of the different processes P and N removal could be attained.
Biochemical Methane Potential of Municipal Solid Waste (MSW) Components
Authors: Owens J. M. , Chynoweth D. P.
Published: May 2018

The biochemical methane potential of several MSW fractions was determined in order to compare extents and rates of their conversion to methane. Based on MSW samples analyzed, the methane yield of MSW was estimated to be as high as 0.20 m3 kg−1 VS added, which indicates that more than 50% of the VS in MSW can be destroyed in anaerobic processing. Yard waste fractions of MSW can be expected to exhibit a high variability in yields due to the variety of plant materials which can be included. While some yard waste components, such as grass, exhibited yields as high as 0.21 m3 kg−1 VS, yields for mixed yard waste were much lower, in the range of 0.14 m kg−1. The make-up of the paper fraction can strongly affect the methane yields of MSW due to variations in methane yields of different paper classes. Bleached kraft papers, regardless of coating, exhibited maximum methane yields of 0.37 m3 kg−1 VS, indicating complete conversion. Unbleached kraft paper found in corrugated box-board exhibited a yield of 0.28 m3 kg−1 VS, while newsprint exhibited yields as low as 0.08 m3 kg−1 VS. Inks used in newsprint did not lower methane yields over unprinted newsprint. The paper used in food packaging was highly biodegradable and its degradation was not affected by polymer coatings when samples were finely ground. These results provide a data base on extent and rates of the major biodegradable organic components of MSW and should be considered when contemplating anaerobic bioconversion of MSW.
Anaerobic Digestion of Olive Oil Mill Effluent Pretreated and Stored in Municipal Solid Waste Sanitary Landfills
Authors: Boari G. , Mancini I. M. , Trulli E.
Published: May 2018

Sanitary landfills of municipal solid waste (MSW) might be used to reduce the storage volume required at plants giving year-round treatment of olive oil mill effluent (OME). A landfill in the methanogenic stage could act as an anaerobic filter and reduce the pollutional load of the OME while also acting as a temporary storage tank.

In the present work, a lysimeter in pilot scale was used to simulate a cell of a sanitary landfill. It was filled with MSW screened by a 80 mm mesh sieve mixed to municipal sludge. Results show that when OME was spread on the top of the lysimeter at a loading rate not exceeding 0.4 kgCOD/d/m3 of reactor steady methanogenic activity was maintained in the layers of refuse and a 70% removal of COD was obtained in the OME leachate collected. Higher loading rates reduced methanogenic activity and COD removal efficiency. Nevertheless, the OME collected from the bottom of the landfill was more easily treated by anaerobic digestion than was the raw OME.
Semi-Dry Thermophilic Anaerobic Digestion of Fresh and Pre-Composted Organic Fraction of Municipal Solid Waste (MSW): Digester Performance
Authors: Mata-Alvarez J. , Cecchi F. , Pavan P. , Bassetti A.
Published: May 2018

The paper presents the results coming from about 2 years of experimentation carried out in a pilot plant digesting fresh and pre-composted mechanically sorted organic fraction of municipal solid waste (MS-OFMSW) in the thermophilic range of temperature (55°C). The process is studied using both substrates at different hydraulic retention times (HRT) and organic loading rates(OLR) in semi-dry conditions, reaching very stressing situations (HRT=6d, OLR=19.9 KgTVS/m3d). Results show the advantage of digesting fresh MS-OFMSW at low HRT (6/8 days), whereas at higher HRT (>12 days) yields improve using pre-composted MS-OFMSW.
The Treatability of Chromium Tannery Wastes
Authors: Kabdasli I. , Tünay O. , Orhon D.
Published: May 2018

Leather processing industry wastewaters contain several conventional pollutants as well as micropollutants. Conventional pollutants can be effectively treated although considerable treatment comprised of several stages is required. However, the potential of conventional methods to remove COD and micropollutants has not been fully explored. The purpose of this paper is to investigate the extent of COD removal by conventional methods. Experimental studies are conducted using raw wastewaters of industries applying chromium tanning to cattlehides and sheepskins. Biological treatability after pretreatment by chemical coagulation is assessed using a lab-scale continuous activated sludge system. Results indicate that chemical coagulation produces wastewaters with a COD of around 2000 mg/l almost independent of raw wastewater quality. Activated sludge operated at 0.17 g BOD5/g MLSS.d loading is found to provide limited nitrification and almost complete BOD5 removal while the COD could only be reduced to around 500 mg/l. The residual COD identified using a newly developed experimental approach shows that it cannot be reduced lower than 300-550 mg/l.
Innovative Two-Stage Process for the Recovery of Energy and Compost from the Organic Fraction of Municipal Solid Waste (MSW)
Authors: Kayhanian M. , Tchobanoglous G.
Published: May 2018

An innovative system for stabilizing the organic fraction of municipal solid waste (OFMSW) has been documented on a pilot scale at the Civil Engineering Department of the University of California at Davis. The system involves the combined methods of high-solids anaerobic digestion and aerobic composting for the recovery of energy and the production of compost from the OFMSW. The performance of the high-solids anaerobic reactor was monitored for three mass retention times. The anaerobic digester was operated under extreme as well as normal conditions. The performance of the aerobic compost unit was monitored based on the physical and chemical characteristics of the final humus by-product. In general, the combined process was very stable at a 30 d retention time and is capable of removing essentially all of the biodegradable fraction of the organic fraction of MSW. A biogas production level of up to 6 liters per liter of active volume of reactor was achieved. The process stability and gas production decreased slightly when the retention time was reduced to 15 d. The output from the second stage is a fine humus-like material with a thermal content of about 14.80 MJ/kg.
Anaerobic Treatment of the High Strength Wastes from the Yeast Industry
Authors: Çiftçi T. , Öztürk I.
Published: May 2018

This paper presents the full-scale anaerobic treatment results from a fermentation plant producing baker's yeast from sugar beet molasses. The process of baker's yeast production generates high strength industrial effluents with a chemical oxygen demand (GOD) of 10 000-30 000 mg/liter. In addition to the sugar containing substances sulphur and nitrogen containing substances are added to the batch processes to promote cell growth and to control pH. This results in rather high concentrations of sulphate 0000-2700 mg/l) and ammonia (400-900 mg/l) in the wastewater.

The treatment plant at Pakmaya Izmit Factory has two different processes: anaerobic first-stage treatment and aerobic second stage treatment. The anaerobic first-stage treatment system includes a buffer tank, an acid reactor, two methane reactors, lamella separators, a gas storage tank and gas burning facilities. The anaerobic reactors were constructed as upflow anaerobic sludge blanket reactors (UASBR) with internal sludge recirculation facilities. The anaerobic reactors have been operating in series mode at mesophilic temperature ranges. Long term Organic Loading Rates (OLR) in the acid, the first and the second stage methane reactors have been averaging 9.8, 8.6 and 3 kg COD/m3·d respectively. Average COD removal is 75 percent in the anaerobic pretreatment stage. Average biogas production is 8000 m3/d, corresponding to a biogas conversion yield of 0.6 m3 per kg COD removed and it is equivalent to a netbioenergy recovery of 40 000 kWh/d.
The Removal of Heavy Metals by Using Agricultural Wastes
Authors: Orhan Y. , Büyükgüngör H.
Published: May 2018

The removal of heavy metals from wastewater using adsorbants such as waste tea, Turkish coffee, exhausted coffee, nut and walnut shells has investigated. Batch studies were conducted at room temperature and adsorption experiments were carried out by shaking 0.3 g of adsorbent with 100 ml synthetic wastewater containing Cr (VI). Cd (II) and A1 (III) metal ions. The remaining concentration of heavy metals in each samples after adsorption at various time intervals was determined spectrophotometrically. Batch studies showed that these adsorbents exhibit a good adsorption potential for A1 (III) metalions. The adsorption ratios of A1(HI) were as 98, 99, 96, 99.5 and 96% for waste tea, Turkish coffee, exhausted coffee, nut and walnut shells, respectively. These results were compared with those obtained using activated carbon as adsorbent. The batch adsorption kinetics and adsorption equilibria were examined and described by a first order reversible reaction and Freundlich isotherm, respectively. The first order rate and isotherm constants have been calculated.
Treatment of Sulfate Containing Wastewaters Using Barium Salts
Authors: Kabdasli I. , Tiinay O.
Published: May 2018

Sulfate treatment especially in industrial wastewaters is gaining importance. Chemical precipitation with barium carbonate is an applicable process for removing sulfate if it proves economically feasible. This paper attempts to evaluate the theoretical basis and limitations of the process. Experiments are run on synthetic and industrial wastewaters to verify and discuss the theoretical predictions. Results indicate that theoretical predictions are accurate enough provided that the mechanisms involved and realistic constants can be defined.
Phosphorus Deficiency Diagnostics in the Eutrophic Rímov Reservoir
Authors: Nedoma J. , Porcalová P. , Komárková J. , Vyhnálek V.
Published: May 2018

In order to assess the occurrence and the degree of phosphorus deficiency, the upper layer (0-2 m) of the eutrophic Římov Reservoir (Czechoslovakia) was sampled from March to October 1990 in one- to three-week intervals. Soluble reactive phosphorus and maximum possible orthophosphate (by Rigler's radiobioassay) concentrations, seston elemental stoichiometry (C/P; N/P), orthophosphate turnover time, and phosphorus deficiency index (= ratio of the primary production to the Vmax of the PO4 uptake) were estimated. Early in spring, during the spring clear-water period, and in the autumn, no indications of P-deficiency were found. Strong P-deficiency was detected in summer (June - September), moderate to strong deficiency also during the spring phytoplankton maximum. The concentration of SRP < 5 µg.1−1 indicates phosphorus deficiency in the Říimov reservoir.
Degradation of Organic Substances in Reservoirs
Authors: Straškrabová V. , Komárková J. , Vyhnálek V.
Published: May 2018

Due to the retention of water in an impoundment, the degradation of easily decomposable organic substances expressed as BOD (“self- purification”) is higher in a reservoir compared to a similar stretch of flowing river. For the same reason, the production of new organic matter by phytoplankton (PP) is also enhanced after impoundment. Data on reservoirs with theoretical retention time (RT) in the range of 1 - 535 days showed that PP reached 9 - 99% of the total input (TI) expressed as BOD (TI = PP + BOD load by inflows). The share of PP increases with increasing RT, decreases with increasing mean depth and depends on the quality of inflows. During 10 years' period, the relation of BOD and PP to bacterial and algal respiration has been examined in a temperate, dimictic, canyon-shaped reservoir. Total budget showed that BOD decrease fluctuated between 70 to 88% of TI, irrespective of the increasing PP during the whole period.
Enhancement of Phosphorus and Nitrogen Removal with a Side Stream Biological Nutrient Removal Process
Authors: Eun Lee Sang , Soo Kim Kwang , Soo Kim Kap , Whoe Kim Chang
Published: May 2018

Bench scale experiments and pilot plant studies (20 m3/day) on a side stream biological nutrient removal process (P/L process) were conducted for 3 years using primary effluent of two different sewage treatment plants as influent. The phosphorus removal efficiency was always higher than 90% resulting in an effluent T-P concentration lower than 0.5 mg/l while total nitrogen removal efficiency of the P/L process was less than 50%. However, total nitrogen removal efficiency could be improved to 88% with some modification of the process.

The presence of nitrate nitrogen higher than 2 mg/l in the phosphorus stripping tank significantly reduced the phosphorus release in the stripping tank. Phosphorus content of the sludge in the aeration basin was about 30% higher than that of the phosphorus stripping tank, however, phosphorus content in the aeration basin could become higher by recycling portions of the phosphorus rich supernatant to the aeration basin to utilize the phosphorus uptake capacity of the sludge in aerobic conditions more efficiently and also to reduce the alum requirement.
The Effects of a Secondary Carbon Source on the Biodegradation of Recalcitrant Compounds
Authors: Lu C. J. , Tsai Y. H.
Published: May 2018

The effects of the addition of a secondary carbon source on the biodegradation of a chlorinated phenol were studied with a series of batch reactors. The biodegradability of chlorinated phenols was shown to follow the decreasing order: phenol > 2,4-DCP > 4CP > 2,4,6-TCP > 2CP > 3CP by the unacclimated microorganisms. The addition of a secondary carbon source may enhance or retard the biodegradation of a recalcitrant compound. The presence of a relatively easily biodegraded compound, such as 2,4-dichlorophenol, enhanced the biodegradation of a less chlorinated but recalcitrant compound, such as 2-chlorophenol. The enhancement of the removal efficiency of 2-chlorophenol was proportional to the concentration of 2,4-dichlorophenol. Monochlorophenols, such as 2-chlorophenol, 3-chlorophenol or 4-chlorophenol generally retarded the biodegradation of the relatively more highly chlorinated phenols, such as 2,4-dichlorophenol or 2,4,6-trichlorophenol.
Upflow Anaerobic Sludge Digestion in a Phase Separation System
Authors: Lin Hsin-Yi , Ouyang Chaio-Fuei
Published: May 2018

This paper aims to expand the knowledge about methods for improving the rate of solids hydrolysis, volatile acid formation and methane gas production. It studies the effects of phase separation and operational modes on the performance of the process. Two systems were investigated. The two-phase system consisted of a CSTR acid-phase digester and an upflow methane-phase digester, the one-phase system comprised of an upflow anaerobic digester. In order to provide optimal contact conditions and recycle liberated indigenous enzymes or cell biomass fractions, continuous recycling of the effluent sludges to the sludge bed of the reactor was used.

In general, the nonbiodegradable portion of the substrates contained in the mixed sludges was found to be about 45% on the basis of TVS. The TVS reduction of the two-phase system was 53%, this is higher than in the one-phase system. Methane production rate and methane content were 0.351 l/g TVS added and 66.6%, respectively.
Research on the Characteristics of Start up and Operation of Treating Brewery Wastewater with an AFB Reactor at Ambient Temperatures
Authors: Yongming Liang , Yi Qian , Jicui Hu
Published: May 2018

The purpose of this study was to evaluate the efficiency and feasibility of treating brewery wastewater with an Anaerobic Fluidized Bed(AFB) reactor at ambient temperatures of about 25°C. Results from nearly one year of tests have demonstrated that the reactor has a volumetric loadings rate of 27-30kgCOD/m3.d with 2.5 h of hydraulic retention time (HRT). The COD removal rate can reach 85% or more under stable operating conditions. The average production rate of biogas was 0.45m3/kgCOD removed, of which the CH4 content was 72%. In addition, the formation mechanism of the biofilm was analyzed, the measures of rapid start up of the reactor was investigated. The operational characteristics of the AFB reactor were also discussed.
A Wastewater Treatment System for an Industrialized Pig Farm
Authors: Chin Kee Kean , Ong Say Leong
Published: May 2018

A demonstration wastewater treatment plant was built to treat the wastewater from a large, intensive farm with a standing pig population (spp) of 25,000 to establish design and operating parameters. The mean wastewater flow was around 500 cubic metres per day (30 l/spp.d) with a peak flow of around 700 cubic metres per day (35 l/spp.d). Treatment processes used during the study period included primary sedimentation, anaerobic digestion for settled solids and an anaerobic lagoon for the treatment of the settled raw wastewater and the discharge from the anaerobic digester. The steady state BOD and COD of the anaerobic lagoon were 1,520 and 3,630 mg/l respectively as compared to the mean BOD and COD respectively of 10,200 and 28,900 mg/l of the raw wastewater. Although close to 80% treatment efficiency was achieved further treatment was necessary to meet the effluent standard of 250 mg/l COD.
Disinfection of Virus in Water by Active Oxygen Species
Authors: Hamada Akira , Hakoda Masafumi , Utsumi Hideo
Published: May 2018

Identification of the species of active oxygen generated in water by chlorination or ozonation was carried out by the spin trapping method using DMPO as the spin trap agent with ESR spectrometry. On chlorinating with NaOCl solution (15 mg/litre), typical ESR signals for DMPO-OH adduct were observed. Increasing the concentration of NaOCl, however, caused complex spectra to appear. The addition of thiourea or D-mannitol, as a radical scavenger, did not significantly affect on the intensity of the signals. On ozonation, two radicals, DMPO-OH and an unknown radical, were always observed. These results indicate the generation of several radicals in the solution treated with NaOCl and ozone.

An interaction of the polio virus with ♦OH was also studied. The preliminary test showed that the ♦OH generated by Fenton's reaction slightly disinfected the virus. Precise tests changing the concentration of active oxygen and the reaction condition are currently in progress.
Oxygen Supply Method Using Gas-Permeable Film for Wastewater Treatment
Authors: Suzuki Y. , Miyahara S. , Takeishi K.
Published: May 2018

Gas-permeable film can separate air and water, and at the same time, let oxygen diffuse from the air to the water through the film. An oxygen supply method using this film was investigated for the purpose of reducing energy consumption for wastewater treatment. The oxygen transfer rate was measured for the cases with or without biofilm, which proved the high rate of oxygen transfer in the case with nitrifying biofilm which performed nitrification. When the Gas-permeable film with nitrifying biofilm was applied to the treatment of wastewater, denitrifying biofilm formed on the nitrifying biofilm, and simultaneous nitrification and denitrification occurred, resulting in the high rate of organic matter and T-N removal (7 gTOC/m2/d and 4 gT-N/m2/d, respectively). However, periodic sloughing of the denitrifying biofilm was needed to keep the oxygen transfer rate high. Energy consumption of the process using the film in the form of tubes was estimated to be less than 40% of that of the activated sludge process.
The Development of Rural Water Supply in the Province of Fayoum, Egypt
Authors: Rahman Abu Hamed Abdel , Sannen A. M. H.
Published: May 2018

The paper provides a case study of rural water supply in Fayoum. First, the present state-of-affairs is described and analyzed with respect to production, consumption and coverage. A water balance is drawn up and the projected trends up to the year 2000 are indicated. Nearly full coverage has been achieved already but still more than 50% of the population is served by public standposts. Considerable demand for house connections is apparent. Based on the present trend it is expected that by the year 2000, 75% of the population could be served by private connections, provided sufficient production capacity becomes available.

Secondly, the focus is on organization and finance with special attention to cost recovery. Estimates for present billing efficiency and the Unaccounted For Water (UFW) percentages are provided. With the perceived trend in the growth of house connections and decline of public taps there is ample potential to reduce UFW, provided an efficient billing and fee collection system is introduced and leakage is controlled. With the reduction of UFW by “technical” measures half of the cost recovery target can be achieved. The other half has to come from tariff increases.

Experience is drawn from the Netherlands-supported Fayoum Drinking Water and Sanitation Project (FADWS) which started in 1990.
Anaerobic Treatment of Domestic Wastewater in Small Scale UASB Reactors
Authors: Bogte J. J. , Breure A. M. , van Andel J. G. , Lettinga G.
Published: May 2018

A survey was made on the feasibility of on-site anaerobic treatment of domestic wastewater from small scale emissions in The Netherlands. Three 1.2 m3 UASB-reactors (Upflow Anaerobic Sludge Blanket) were tested in different rural locations. The survey made clear that the efficiency of the process is highly dependent on the reactor temperature. Below 12 °C purification was predominantly based on settling, while above 12 °C microbial degradation of organic matter increased. Efficiencies for the removal of total COD and BOD of two of the reactors ranged between 33 and 60%, equalising well performing septic tanks. In one of the reactors the average production of biogas, with a methane content of 78%, was 67 liters per day. Complete transformation of volatile fatty acids (VFA) into biogas was achieved during 3 to 4 months a year at temperatures above 15 °C. In this period, during the second year of operation, the average efficiencies for COD and BOD removal were 60 and 72% respectively, while the maximum gas production reached 300 liters per day. In the latter period the mineralisation rate exceeded the input rate of organic matter, resulting in a decrease of settled material in the reactor. The possibility of high efficiencies during summertime in The Netherlands and the positive results of similar experiments in Indonesia and Latin America lead to the conclusion that anaerobic digestion is a promising process for the (pre-)treatment of domestic waste water in (sub)tropical countries.
Assessment of the Performance of Oxidation Pond System for Wastewater Reuse
Authors: El-Gohary F. , Abdel Wahaab R. , El-Hawary S. , Shehata S. , Badr S. , Shalaby S.
Published: May 2018

A study has been conducted to evaluate the performance of an aerated oxidation pond system in a village in Egypt. It comprises an anaerobic pond (AP), an aerated facultative pond (AeP) and a maturation pond (MP). The assessment involved an intensive programme of sampling and analysis of raw wastewater, unit process contents and unit process effluents.

Field studies indicated a wide fluctuation in the BOD5 load applied to the STP. It ranged from 64 to 290 g BOD5/m3.d, with an average value of 146 g BOD5/m3.d. This, however, did not affect physico-chemical characteristics of the final effluent. Residual COD, BOD & SS were around 99 mg/l, 32 mg/l & 66 mg/l, respectively. Although faecal coliform removal was around 98.9%, yet residual count was still high. Also, significant decline in both parasitic eggs and protozoal stages has been recorded.
Impact of the Reuse of Domestic Waste Water for Irrigation on Ground Water Quality
Authors: Farid M. Samir M. , Atta Samir , Rashid Mohamed , Oude Munnink Josefien , Platenburg Ruud
Published: May 2018

Egypt planned to reclaim large areas in both the Eastern and Western desert fringes of the Nile Delta with an increasing use of sewage effluent from Greater Cairo. The Gabal el Asfar farm which has been irrigated with raw to primary treated sewage effluent for a period of seventy five years was selected as a pilot area to investigate the groundwater quality. This farm covering 3000 feddan (1250 ha), is located in the sandy area northeast of Cairo.

The main objective of the study was to assess the impact of agricultural application of sewage effluent on groundwater quality. Observation wells were constructed and field and laboratory measurements were carried out in and around the Gabal el Asfar area. The water balance and mass balances have been assessed. The study yielded useful recommendations to decrease the impact on groundwater quality and possible risks in Gabal el Asfar, concerning 1) type and amount of pollution from sewage effluent, 2) design criteria to control possible spreading of pollutants, and finally 3) the use of groundwater in the area. The following comprises the main conclusions:*Irrigation with sewage effluent had a positive impact on salinity of the initially brackish groundwater. On the contrary, groundwater quality is negatively affected from sewage effluent with regard to nitrogen contents (ammonium and nitrate), phosphate, heavy metals and faecal coliforms.*The drinking water limit for nitrate is sometimes exceeded. Moreover, faecal coliforms are found in water from all shallow handpumps in the area. The general suitability of the groundwater is therefore limited while the use of handpumps for drinking water purposes should be avoided. High boron contents of sewage effluent indicate a risk for crops sensitive to boron.*The accumulation of heavy metals and phosphorus in the soil adversely affects the soil system.*Pretreatment of sewage effluent in Gabal el Asfar should be improved to limit the pollution of the aquifer. Industrial discharge in sewage effluent should be avoided.*Groundwater recharged by sewage effluent is mainly collected by drains in or at the borders of the area, so spreading of pollutants out of the area is largely controlled.
Removal of Toxic Metal Ions from Solutions Using Industrial Solid Byproducts
Authors: Zouboulis A. I. , Kydros K. A. , Matis K. A.
Published: May 2018

Nowadays the problem of industrial wastes handling and disposal is increasing continuously, as more strict environmental considerations have to be taken into account. In this paper, selected experimental results are presented from our current research in toxic metals removal (e.g. Cu, Pb, As), related to the applications of mineral particles as by-products (red mud, pyrite, dolomite, etc.) for the induced removal of toxic metals from aqueous solutions. These by-products, existing in finely divided form and considered rather as solid industrial wastes, have been used as a cheap solid adsorbent or substrate. Appropriate methods for the subsequent solid/liquid separation were examined, among them flotation. Different parameters were tested and high removals of toxic metals were achieved. In this way, a useful application may be realized for the waste mineral particles.
Dynamic Behavior of Intermittent Buried Filters
Authors: Boller M. , Schwager A. , Eugster J. , Mottier V.
Published: May 2018

Buried filters were investigated experimentally in pilot and full scale as typical on-site treatment for small wastewater flows. The filters were operated by intermittent flushing which causes the water and the pollutant transport through the unsaturated media to be of a highly dynamic nature. Water transport and tracer studies at low and high hydraulic flush loads revealed frequent flushing at low loads to be superior to less frequent flushing at high loads for treatment of the same daily amount of wastewater. These findings were confirmed in a full scale plant through monitoring of the dynamic washout of unoxidized matter in terms of COD and NH4+ after application of different hydraulic loads. The moisture retention capacity of the filter media correlated to the grain size distribution was found to be an important parameter. COD-removal and nitrification rates depend strongly on the oxygen supply to the media. In general, the oxygen diffusion into the media and the air exchange, induced by intermittent flushing, are sufficient. However, when applying relatively large hydraulic loads and coarse filter grains, especially in the range above 1 mm, buried filters tend to larger breakthroughs of unoxidized matter due to short retention times and instantaneous lack of oxygen. Experiments on average treatment performance were carried out and showed that under optimized conditions even wastewaters containing relatively high ammonia contents (150 gNH4+-N/m3) can be fully nitrified when limestone type filter material is used. Full scale operation revealed further that careful pre-treatment (e.g. septic tank) for the removal of most of the suspended solids is necessary to guarantee safe operation.
Wastewater Treatment over Sand Columns – Treatment Yields, Localisation of the Biomass and Gas Renewal
Authors: Guilloteau J. A. , Lesavre J. , Liénard A. , Genty P.
Published: May 2018

Domestic wastewater treatment by infiltration-percolation is a process that is becoming common in France. The aim of this study is to find the depth of biologically active substrate in an infiltration basin by determining the depth of the media colonised by the biomass and by studying oxygen renewal mechanisms. The study using sand columns has allowed simultaneous comparison, on the same profile, of biomass content (ATP), gaseous composition (chromatography) and the variations of the effluent quality (carbon, nitrogen, phosphorus). Down to a depth of 30 cm, removal rates achieved in terms of conventional treatment parameters are very high (COD and SS > 90%, NH4+ ≈ 95%, total phosphorus ≈ 50%). Beyond a depth of 15 cm, the biomass content (expressed in ATP) is ten times less than at the surface, and virtually ceases to develop.

Monitoring of O2 levels points to the need for drying periods in order to ensure natural ventilation of the basins. The primary settling stage must be effective in order to avoid any risk of clogging which would prevent the air from being renewed by diffusion.The length of the drying period must be almost double that of the flooding period to allow the media to recover as much of its treatment capacity as possible.

This study pinpointed the depth of the biologically active substrate at arround 30 cm. The data obtained from this trial project point to the following design criteria: 1.5 m2/p.e. spread over three basins, and a drying period twice as long as the flooding period. The sand depth will depend on the plant's overall water quality objectives: around 0.50 m for the removal of carbonaceous pollution and nitrification of Kjeldahl nitrogen, a greater depth for disinfection purposes.
Coupling of Reed Bed Filters and Ponds: An Example in France
Authors: Liénard A. , Boutin C. , Bois R.
Published: May 2018

The study of wastewater treatment series based on the use of macrophyte beds, in accordance with a design initially developed in Germany by Dr. Seidel, was initiated by CEMAGREF in 1983. The number of plants constructed was deliberately limited and they were subject to regular assessments and improvements. It was thus shown that only reed bed filters that were drained and alternately fed, were able to handle a pollutant load of the order of 80 g COD m-2 day-1 with satisfactory treatment reliability over a period of several years. The Gensac la Pallue plant, in the Charente department, is original since it combines this type of filter in the first treatment stage with three microphyte ponds designed with a low theoretical residence time of 21 days (compared with the usual residence time of 30 days in tertiary treatment). The whole treatment series only occupies an effective surface area of approximately 6 m2 per p.e. (about 1 m2 and 5 m2 for filters and ponds respectively).

After 5 years of operation and monitoring, it has been clearly established that filters dosed with raw wastewater at a rate of 65 g of COD and 30g of TSSm-3 per day, regularly achieve a removal rate of 70 to 85 % of these same elements without clogging. The daily hydraulic load that the filter can withstand in service regularly exceeded 2 metres in the month of November 1992.

The ponds finish the treatment and this article limits itself to analysing results relating to the elimination of nutrient, which reaches 35% for nitrogen and 55% for phosphorus. Residence times that are too short in winter, in conjunction with a large part of the sewerage system being of combined type, can sometimes temporarily lead to an increase in the amounts of nitrogen and phosphorus discharged to the natural environment.
Performance of Static Flocculators
Authors: Bhole A. G.
Published: May 2018

The conventional mechanical flocculator consisting of paddles and other mechanical equipment such as a gear box, revolving foot-bridge etc. and requiring electrical energy for operation is not suitable for rural areas of developing countries. Hence four models of static flocculators which do not involve any moving parts or mechanical equipment and do not require electrical energy for operation were fabricated and tested for hydraulic properties such as dead space and short circuiting. The relative performance of the four models was tested for four turbidities and rates of flow.
Treatment of Wastewater by Stabilization Ponds – Application to Tunisian Conditions
Authors: Ghrabi A. , Ferchichi M. , Drakidès C.
Published: May 2018

An experimental study of the domestic wastewater treatment in a series of four pilot-scale stabilization ponds was conducted. The objective was to adapt the treatment by waste stabilization ponds (WSP) to Tunisian conditions. The obtained results show that the average values of removal are about 72% for BOD, 65% for COD and more than 50% for ammonia nitrogen. The phosphate concentration was influenced by release of phosphate from decomposition sediment The elimination of total coliform, faecal coliform and faecal streptococci is between 99.3% and 99.99%. The most rate reduction was registered during the warm months which coincide with the irrigation season. The sediment accumulation is taken mainly in the first pond: the deposition rate is high (5 cm/year). In the three maturation ponds, it ranges from 1.3 to 1.6 cm/year. The WSP can be designed to satisfy Tunisian conditions. Because of favourable climate, loading can be much higher than those reported in the literature and some of the disadvantages of the pond system can be reduced. So we can economize in evaporation of effluent which is considered as a resource of irrigation in agriculture and we can reduce the surface area.
Intermittent Aeration for Nitrogen Removal in Small Aerated Lagoon
Authors: Koottatep S. , Leesanga C. , Araki H.
Published: May 2018

Intermittent aeration has been proved to be an efficient method in nitrogen removal in many biological treatment processes. Aerated lagoon has been used as domestic wastewater treatment for a small housing estates in Thailand for quite sometime. The purpose of this study is to determine whether intermittent aeration of aerated lagoon could provide efficient nitrogen removal in domestic wastewater. The experiment was carried out using pilot scale aerated lagoon at Chiangmai University. The result showed that 45% of total nitrogen removal could be achieved by aeration and non-aeration of 12 hours each cycle. The intermittent aeration did not affect organic substances removal of the process. Sludge recycle during non-aeration period may improve total nitrogen removal. The method could be introduced to save energy of small wastewater treatment plant.
Preformed Ferric Hydroxide Flocs as Adsorbents of Humic Substances
Authors: Cathalifaud G. , Wais Mossa M. T. , Mazet M.
Published: May 2018

The purpose of this study is to show that previously built flocs obtained by the coagulation-flocculation of kaolinite suspension with ferric chloride are a potential adsorbent of humic substances.

Flocs are prepared from kaolinite (< 50 µm) and FeCl3 according to the jar-test technique:after 3 minutes of rapid mixing at pH = 5.4 ± 0.1, 30 minutes of slow mixing, humic acids are added for a contact time of 6 hours; the effects of calcium, sodium salts (chloride, sulphate) on the adsorptive capacity of preformed flocs are also studied. The results indicate that the preformed flocs are good adsorbent materials. Langmuir equation is used to determine adsorption capacities.
Effect of Pre-Ozonation on Organics Removal by In-Line Direct Filtration
Authors: Tobiason J. E. , Edzwald J. K. , Reckhow D. A. , Switzenbaum M. S.
Published: May 2018

A pilot-scale study of the effects of pre-ozonation on the performance of in-line direct filtration was carried out. Performance measures included filtered water turbidity, unit filter run volumes, and organics in filtered waters: DOC, UV254, AOC and DBPs. Continuous operation of four dual media GAC/sand filters with and without pre-ozonation and chlorinated backwash and a dual media anthracite/sand filter were compared to full-scale performance. Pre-ozonation frequently results in longer filter runs, causes a twofold increase in raw water AOC and has little effect on raw water DOC. GAC/sand filters consistently reduced the AOC in the ozone train to levels below that of the full-scale plant and also provided 25 % lower DOC levels as compared to anthracite/sand filters. The effect of ozone and filtration on chlorinated DBPs followed overall DOC removal while DBPs created by ozonation followed AOC removal trends.
Ferric Chloride Coagulation for Removal of Dissolved Organic Matter and Trihalomethane Precursors
Authors: Amirtharajah A. , Dennett K. E. , Studstill Anne
Published: May 2018

Ferric chloride coagulation of two types of natural dissolved organic matter was studied. The molecular weight distribution of Suwannee River humic substances currently used as an international standard was characterized using fast atom bombardment mass spectrometry (FABMS). The molecular weight distributions were characterized before and after coagulation. Ferric chloride dosage and pH domains on the iron coaglation diagrams were developed for removal of these humic substances and for determination of the resulting trihalomethane formation potentials (THMFP) of the treated water. The results indicate that it is possible to maximize the removal of dissolved organic matter and minimize trihalomethanes by coagulation only under very specific conditions of pH and ferric chloride dosage.
Precipitation and Coagulation of Organic Substances in Bleachery Effluents of Pulp Mills
Authors: Beulker S. , Jekel M.
Published: May 2018

The formation of chlorinated organic substances in bleachery effluents of pulp mills is avoided by changing the bleaching processes to nonchlorinating agents. However, high concentrations of poorly biodegradable and colored lignins are remaining. Precipitation can be one option in physico-chemical treatment of these waters. The influence of alum, lime and magnesium hydroxide as precipitation agents for two different bleachery wastewaters was investigated under various conditions. Alum prove to be the most effective precipitant. Application at an Al/DOC-ratio of 0.5 (g/g) yields a reduction of about 60 % of the soluble organic matter in chlorine-bleachery effluents at the pH = 5.5. Oxygen-bleachery effluents require only half of this specific dosage. Lime precipitation also causes low residual concentrations, but the high chemical demand leads to problems in application. The precipitation with magnesium hydroxide cannot be applied, because remaining concentrations of organic materials are quite high. The changes in bleaching processes are responsible for a new kind of wastewater, which has a significantly lower demand of precipitant