bluuebunny/crossref_metadata_2025 huggingface dataset:
Co-digestion of organic solid waste and sludge from sewage treatment
Authors: Edelmann W. , Engeli H. , Gradenecker M.
Published: May 2018

Solid organic wastes were codigested together with sludge of a sewage treatment plant (STP). In the practical part of the study, a plant to pretreat the organic solid wastes provided by local super markets was constructed at the STP of Frutigen, Switzerland. Up to more than 1 cubic metre of wastes was added to the fermenter of the STP every day. Data collected during 14 months of practical works, showed that for raw fruit and vegetable wastes a two step pretreatment is necessary: First the wastes were chopped and afterwards reduced to a size of 1-2 millimetres, in order to get a homogeneous suspension together with the primary sludge. The vegetable wastes showed excellent digestibility: They seemed to accelerate the digestion process as well as to increase the degree of the anaerobic degradation of the sludge. The energy demand for both, pretreatment and digestion, was 85 kWh/ton of fresh wastes. 20% of the energy was used for the hygienization, a step which does not seem to be necessary for this kind of waste in most of the cases, however. After using the gas for energy conversion, a net yield of 65 kWh/ton of electricity and 166 kWh/ton of heat was measured. Treating cooked kitchen wastes, the net energy production will be higher, because in this case a one step pretreatment will be sufficient. The pretreatment and treatment costs for codigestion on STP's were calculated to be in the range of 55 US$/ton treating half a ton per day and 39 US$/ton treating one ton, respectively. A theoretical feasibility study showed that in Switzerland there is a short term potential on STP's for the codigestion of about 120,000 tons of biogenic wastes per year without big investments. Economic studies about codigestion on agricultural biogas plants showed that the codigestion is a must at the current energy prices, which are far too low for agricultural AD without an additional income by treating solid wastes for third parties.
Microbially mediated attenuation potential of landfill bioreactor systems
Authors: Pohland F.G. , Kim J.C.
Published: May 2018

The origin and fate of landfill leachate and gas constituents generated during the sequential phases of solid waste transformation and stabilization are emphasized within the perspective of the in situ processes of microbially mediated attenuation. The fundamental biochemical and physicochemical reaction mechanisms are presented in terms of their spatial and temporal dimensions and their significance for transformation of both nonhazardous and hazardous waste constituents. Supporting information from laboratory, pilot-scale and full-scale applications is used as a basis for interpretive analysis and for providing operational guidance and promoting future developments.

The diversity, domains, and functional interdependence of the acidogenic, methanogenic, sulfate and nitrate reducing, nitrifying and denitrifying, and methanotrophic consortia are addressed in order to reveal opportunities for landfill process modifications and associated operational optimization. Controlled attenuation, linked with operational and regulatory realities, are used to suggest innovative landfill configurations involving prospective compartmentalization and integrated waste loading, dedicated treatment zones for in situ transformation of waste and leachate constituents with associated gas capture, control and utilization. Monitoring requirements are emphasized to provide guidance and feedback for operational control and environmental compliance. Finally, technology needs for establishing a more unified approach to the development and management of bioreactor landfills are presented.
Effect of substrate-seed mixing and leachate recirculation on solid state digestion of biowaste
Authors: Veeken A.H.M. , Hamelers B.V.M.
Published: May 2018

Lab-scale experiments were performed and a mechanistic model was developed to simulate the solid state digestion of biowaste in a batch reactor. Both experiments and model showed that the substrate-seed mixing degree and leachate recirculation rate have a strong effect on the reactor performance. This is due to mass transport limitations of volatile fatty acids (VFA) within the biowaste-seed bed. In that case two regions are developed in the digester, so-called acidogenic and methanogenic pockets. Limitations in mass transport will prevent irreversible acidification during start-up of the reactor because whereas high VFA concentration is met in the fresh waste pockets, the VFA concentration in the methanogenic pockets will remain low. However, accumulation of VFA in the acidogenic pockets will reduce the hydrolysis rate of biowaste due to inhibition by VFA. Moreover, experiments and simulations showed that the reactor performance can be improved by varying the leachate recirculation rate or applying sequential batch operation.
Anaerobic digestion of solid waste: state-of-the-art
Authors: De Bere L.
Published: May 2018

In order to make a correct assessment of the state-of-the-art of the technology, a study was made on the development of digestion capacity for solid waste in Europe. The study was limited to plants in operation or under construction that were treating at least 10% organic solid waste coming from market waste or municipal solid waste. A total treatment capacity for solid waste organics, excluding the tonnage used for sewage sludge and manures, evolved from 122,000 ton per year in 1990 to 1,037,000 ton available or under construction by the year 2000 in 53 plants across Europe, an increase by 750%.

Both mesophilic and thermophilic technologies have been proven, with about 62% of capacity being operated at mesophilic temperatures. Wet and dry digestion are almost evenly split, while a clear choice was made for one-phase systems instead of two-phase systems, which represent only 10.6% of capacity. The capacity provided by co-digestion systems is limited, while there is a rising interest in digestion of mixed household waste.

The reliable performance has been demonstrated for all types of anaerobic digestion systems. On the basis of the Dranco technology, a single-phase thermophilic dry digestion process, performances were reached similar to high-rate wastewater digestion. An annual average loading rate of 18.5 kg COD/m3.day, resulting in a biogas production of 9.2 m3/m3reactor.day was obtained at a full-scale plant. The plant operated at a retention time of 15.3 days. Feedstocks range from clean organic wastes (31% dry matter) to heavily polluted grey waste organics (57% dry matter). Average dry matter concentrations of the digested residue of 41% were obtained.
Odour measurement: A code of practice
Authors: Sneath R. W. , Clarkson C.
Published: May 2018

Odour emission is as much a part of the adverse effect of any new or existing process as noise, water pollution, VOC emissions or radiation. It is essential to quantify it whenever plans are being made for new or modified processes.

The first aspect of quantification of odour emission is the need to use a standard method of measurement of odour concentration. Aswith liquid effluents where we use standard laboratory methods for each characteristic, e.g. BOD, COD, TSS etc., the analysis method for measurement of odour concentration is the CEN/TC264/wg2 (draftprEN13725) standard (ComittéEuropéen de Normalisation/Technical committee 264/Working Group 2). This standard is often specified in tender documents as the methodology to be used in the assessment of abatement equipment performance. In this paper the standard, with what it can and can not do, is described in detail.

The second aspect is that methodologies should be agreed for sample collection. The collection protocol, at the lowest level, is agreed so that significant day to day comparisons can be made. More rigorous protocols must be drawn up when legal requirements need to be met so there is consistent enforcement of regulations or discharge consents.

It is most important that a representative odour sample is collected from the source. This is most problematic when the odour is emitted from a large surface either with or without airflow through it. Best practice methods are presented and discussed. The statistical significance of the analysis, as with any other measurement, depends upon the precision of the laboratory analysis and the number of samples analysed. An example will be used to illustrate the importance of calculating the number of samples required for a given purpose.
Monitoring of wastewater odours using an electronic nose
Authors: Stuetz R. M. , Fenner R. A. , Hall S. J. , Stratful I. , Loke D.
Published: May 2018

The recent availability of commercial electronic nose instruments for odour detection may offer a rapid and relatively simple technique for monitoring wastewater odours. Results have been reported that for sewage odours from a single source a robust relationship can be found between the responses patterns of a sensor array (consisting of 12 conducting polymers) and their associated sewage odour concentrations. However, the initial application of this technology in the field of sewage treatment may not be for detecting nuisance odours but for wastewater monitoring and/or process control of a treatment works. A comparison between the odour profiles of sewage liquids and corresponding BOD, COD, TOC measurements has demonstrated the ability of a non-specific sensor array to detect changes in the organic content of a wastewater sample. Statistical analysis of the sensor response patterns with BOD value (for sewage samples from the inlet works, settlement tanks and the final effluent outlet) over a 5-month period, showed that for longer time periods the relationship between these parameters was essentially non-linear, but that over shorter time periods a linear relationship was evident. The findings showed that a number of different wastewater quality relationships could be formulated from the same electronic nose analysis of a sewage liquid. This suggests that the organic content of a wastewater, as well the potential of a wastewater to produce nuisance odours, could be predicted from a single headspace analysis of a sewage liquid using a sensor array.
Analaysis of volatile odour compounds in digested sewage sludge and aged sewage sludge cake
Authors: Winter P. , Duckham S. C.
Published: May 2018

A number of malodorous compounds were identified in digested sludge and the corresponding sludge cakes. The major components included a number of sulfides. The levels of these compounds were monitored in order to investigate the influence of the sludge treatment process and length of cake storage on the malodour of treated sewage sludge. Two sewage treatment works (STWs) were surveyed. One of the works (Site B) produced very malodorous sludge cake, whilst the other produced a much less odorous cake (Site A). The analysis consisted of purge and trap sampling of liquefied samples followed by gas chromatography-mass spectrometry (GC-MS). Afteran initial screening of samples, by full mass scan GC-MS analysis, targetcompounds were identified for quantification. Sulfide levels inthe majority of the liquid digested sludges were significantly lower than that in sludge cakes. Large differences in the level of sulfides were found in stockpiled sludge cakes. The majority of malodorous sludge cakes had higher sulfide levels than less odorous sludge cakes. The most abundant compounds were dimethylsulfide, dimethyldisulfide and dimethyltrisulfide. Thehighest sulfide levels were found during the first month of stockpiling. Whenthe odour threshold concentration of these compounds was taken into account and odour unit values were calculated, dimethyltrisulfide was found to have a proportionally greater impact on odour than any of the other compounds studied. The use of sulfide levels as indicators of malodour formation and possible strategies for reducing odour in stockpiled sludge cake are discussed.
Odour nuisance – advantages and disadvantages of a quantitative approach
Authors: Yang G. , Hobson J.
Published: May 2018

The benefits of a quantitative approach to odour nuisance may be thought obvious: much better value for money should be obtained from abatement measures. New works can be appropriately sited and appropriately designed. Thesebenefits are only realised however if the quantitative approach chosen is reliable. The components of possible quantitative approaches, – olfactometry – estimates of emission rates – dispersion models – quality standards, are discussed with the limitations and sources of error in each. When using a quantitative approach it is necessary to distinguish between a poor method in which the levels of error are unknown and a good method for which the levels of error can be defined. A quantitative approach should allow different methods for odour control: septicity control using chemicals, operational modifications to reduce turbulenceand covering and treatment of air, to be evaluated on a common footing.
A bioscrubber for hydrogen sulphide removal
Authors: Koe L. C. C. , Yang F.
Published: May 2018

A study was carried out to investigate the feasibility of using treated wastewater effluent to support the operation of a fixed-film bioscrubber for odorous H2S removal. A laboratory scale fixed-film bioscrubber was set up using bacteria of the genus Thiobacillus. The bacteria were isolated from a sample of municipal sludge, cultured in the laboratory and immobilised onto the scrubber's plastic packing media by an immersion method. Series of experimental runs were carried out to determine the optimal operational conditions for the bioscrubber. Results indicated that for the gas retention times equal to or exceedingfive seconds, and with a H2S loading rate below 90 g-H2S/m3-hr, the bioscrubber could remove H2S and odour with efficiencies greater than 99%. The behaviour of the bio-scrubber under various operation scenarios arepresented and discussed in this paper.
Risk assessment model for a waterborne outbreak of cryptosporidiosis
Authors: Gale P.
Published: May 2018

Counts of Cryptosporidium oocysts in 100L volumes of treated water are simulated for conditions representative of a waterborne outbreak in a surface water-derived supply. Assuming oocysts act independently during infection, the risk of infection is directly related to the arithmetic mean oocyst density in the water supply, which is in turn related to the total number of oocysts which break through treatment. Spatial/temporal heterogeneity of oocyst concentrations in the treated water contributes to monitoring programmes based on “spot-sampling” underestimating the arithmetic mean oocyst density and hence the risk of infection. This could contribute to the reported lack of a clear association between oocyst concentrations measured in drinking water supplies and the risk of waterborne outbreak of cryptosporidiosis in the population. An increase in spatial heterogeneity of oocysts during treatment could also contribute to an overestimation of the net oocyst removal by treatment.
Impact of a wastewater treatment plant on Cryptosporidium oocysts and Giardia cysts occurring in a surface water
Authors: Carraro E. , Fea E. , Salva S. , Gilli G.
Published: May 2018

The aim of this study was to assess the impact of a municipal wastewater treatment plant (MWTP) on the occurrence of Cryptosporidium oocysts and Giardia cysts in the receiving water. All MWTP effluent samples were Giardia and Cryptosporidium contaminated, although low mean values were found for both parasites (0.21±0.06 oocysts/L; 1.39±0.51 cysts/L). Otherwise, in the raw sewage a greater concentration was detected (4.5±0.3 oocysts/L; 53.6±6.8 cysts/L). The major occurrence of Giardia over Cryptosporidium, both in the influent and in the effluent of the MWTP, is probably related to the human sewage contribution to the wastewater. Data on protozoa contamination of the receiving water body demonstrated similar concentrations in the samples collected before (0.21±0.07 oocysts/L; 1.31±0.38 cysts/L) and after (0.17±0.09 oocysts/L and 1.01±1.05 cysts/L) the plant effluent discharge. The results of this study suggest that the MWTP has no impact related to Giardia and Cryptosporidium river water contamination, and underline the need for investigation into the effectiveness of these protozoa removal by less technologically advanced MWTPs which are the most widespread and could probably show a lower ability to reduce protozoa.
An optimised and standardised test to determine the presence of the protozoa Cryptosporidium and Giardia in water
Authors: Stanfield G. , Carrington E. , Albinet F. , Compagnon B. , Dumoutier N. , Hambsch B. , Lorthioy A. , Medema G. , Pezoldt H. , de Roubin M-R. , de Lohman A. , Whitmore T.
Published: May 2018

With funding from the European Commission, a consortium of members of the European Water Research Institutes is carrying out a programme of work with the objective of optimising and standardising a method for determining the presence in water of (oo)cysts of Cryptosporidium and Giardia. Each of the stages of the conventional analysis procedure (initial concentration, recoveryand identification and enumeration) are being investigated and the relative merits of existing and new methods are being assessed. Newly developed filters (Envirochek and Filta-Max) have been shown to be more efficient for initial recovery of (oo)cysts from water than the previously used Cuno cartridge filters. In addition, for the analysis of raw waters, flocculationwith ferric sulphate has been shown to give recoveries similar to the Envirochek and Filta Max.

Modern purification systems such as immunomagnetic separation have also been assessed and found to offer some advantages over flotation although optimisation of the latter has brought improved efficiency. Preliminary assessment of solid phase cytometry has indicated that this technique could offer significant time savings compared to conventional microscopic counting. The results of the study will be used to propose a revised standard method to CEN.
Transforming sludge into a recyclable and valuable carbon source by wet air oxidation
Authors: Djafer M. , Luck F. , Rose J. P. , Cretenot D.
Published: May 2018

The wet air oxidation (WAO) process generates residual solids that can be landfilled without additional treatment. This practical advantage stems from the intrinsic leaching-resistant behaviour of the solids, which is linked to the treatment conditions in water at high temperature and to the composition of the solids. X-ray analysis confirmed that the fine powder (diameter 2–6 μm) mainly comprises aluminium phosphates, kaolin, quartz, calciteand an amorphous fraction which immobilises heavy metals in the form of hydroxides, carbonates and insoluble phosphates. The residual solids contain a low amount of organic matter (1–2 wt.% TOC, depending on the process parameters). They are easily settled and dewatered with dry solids (DS) content between 50 and 60%. The re-use of WAO sludge supernatant as a carbon source in biological denitrification have been investigated. Theinitial results are deemed very satisfactory. The most significant results obtained during process development are reported in this paper.
Performance and economics of BNR Plants in the Chesapeake Bay Watershed, USA
Authors: Randall C.W. , Ubay Cokgor E.
Published: May 2018

The performance and economics of four recently constructed or modified BNR municipal wastewater treatment plants located in the Chesapeake Bay Watershed, USA were evaluated, and compared to a treatment plant implementing chemical phosphorus removal and complete nitrification. Phosphorus removal has been very reliable to effluent concentrations below 0.5 mg/L without chemical addition or effluent filtration at BNR plants that have been operating for more than two years. Significant variation was observed in the wastewater characteristics, and this has affected biological phosphorus removal. Chemical precipitation effluent TP concentrations have averaged less than 0.1 mg/L.The small BNR plant was clearly the most costly to operate per 1000 m3/d of flow, which illustrates economy of scale. The chemical precipitation plant was generally more expensive to operate than the large BNR plants.
Complete decomposition of biological waste sludge by thermophilic aerobic bacteria
Authors: Sakai Y. , Aoyagi T. , Shiota N. , Akashi A. , Hasegawa S.
Published: May 2018

Conventional activated sludge (AS) process is an economical and effective biooxidation process although a large amount of excess sludge is necessarily generated. We have developed a new zero-discharge AS process, in which no excess sludge is generated. It was formed by combining the conventional AS process with thermophilic aerobic sludge digester in which excess sludge is solubilized by thermophilic enzyme, so we call it hereafter the digester S-TE reactor. The excess sludge withdrawn from the AS step is subjected to the S-TE reactor, followed by its circulation to an aeration tank. Complete decomposition of the excess sludge is carried out when the sludge is solubilized by thermophilic aerobic bacteria (e.g. Bacillus sp.) and mineralized by mesophilic bacteria. The S-TE reactor is operated at 65°C with hydraulic retention time of 1 day. Bench-scale test facilities of both the new process and conventional AS process were comparatively operated under the conditions of BOD-SS loading of 0.3 kg/kg/dand MLSS of 2,000 mg/L using artificial wastewater for over 100 days. The S-TE reactor was initially inoculated with the seedling culture of isolated Bacillus sp. bacteria. No additional inoculation seem to be needed under the steady condition since these bacteria can form spores and survive even under mesophilic conditions. The average rates of VSS solubilization and VM removal in the S-TE reactor were 40% and 15%, respectively. No excess sludge was generated when 3-fold amounts of the excess sludge generated in the conventional AS process were subjected to the S-TE reactor. In the new process, BOD was removed with high efficiency. Slight increase of SS and TOC was observed when compared with those of the AS process. A pilot-scale facility of the process has been operated with a petrochemical plant wastewater for a year. MLSS concentration was continuously kept around 3,000 mg/L without withdrawing the excess sludge. Inorganic salts seemed not to accumulate in the process. Therefore, it was demonstrated that excess sludge generation was completely reduced in the new process. According to our estimates, total operating costs for the new process are reduced to 40-50% of those of the conventional wastewater dewatering process. An application to a municipal sewage sludge treatment is currently performed in its full-scale facility.
Concept development for the optimisation of the Hamburg Wastewater Treatment Plants
Authors: Ladiges G. , Bertram N-P. , Otterpohl R.
Published: May 2018

The Hamburger Stadtentwässerung (HSE) is planning to take on a further approximately 250,000 PE in addition to the 1.85 m PE already served by its combined wastewater treatment plants at Köhlbrandhöft/Dradenau. To cope with the increased load, a concept for the extension of the plants had to be developed. Various concepts were compared and evaluated using a dynamic computer simulation. The very wide-ranging simulation study showed that the required effluent standards can still be achieved after the volume of the sludge liquor storage capacity has been increased. As many concepts had been assessed in detail, the final solution chosen was considerably less expensive than if the wastewater treatment plants had been extended in a traditional manner.
Reduction of the content of organic micropollutants in digested sludge by a post-aeration process - a full-scale demonstration
Authors: Knudsen L. , Kristensen G. H. , Jørgensen P. E. , Jepsen S.-E.
Published: May 2018

Surplus wastewater sludge reused for agricultural purposes must observe certain limit values with respect to different xenobiotic substances. The latest revision of the statutory order in Denmark includes for the first time a list of limit values on organic micropollutants in sludge. Four groups of micropollutants are included in the list (LAS, PAH, NPE, and DEHP). The limit values will be revised in June 2000, at which time up to 50% of the sludge used for agricultural purposes, will not comply with the standards. It has been observed that the level of organic micropollutants is much higher in anaerobically digested sludge than in aerobically stabilised sludge. This indicates that the organic micropollutants in question can be partly or fully degraded under aerobic conditions but not under anaerobic conditions. The observations have formed the basis of the development of a post-aeration process for biological degradation of organic micropollutants in anaerobically digested sludge with the aim of enabling continued reuse of the sludge for agricultural purposes. The process is presented in this paper together with a description of a full scale demonstration experience on a Danish wastewater treatment plant © 1999, IAWQ. Published by Elsevier Science Ltd.
Cost-effective upgrading of the Arnsberg WWTP by post denitrification with a moving bed system
Authors: Jardin N. , Rath L. , Sabin A. , Schmitt F. , Thöle D. , Kühn S.
Published: May 2018

On the basis of a cost-benefit analysis it was decided to expand the Arnsberg WWTP by a multistage biological process which allows for cost-effective integration of the existing facilities. Carbon removal will then be accomplished in a high-loaded activated sludge stage for which the existing primary clarifier is to be reconstructed. The existing trickling filters will be used for nitrification during a midterm period and will be replaced later on either by a moving bed system or by new trickling filters. Line 3 of the existing secondary clarifiers will be reconstructed and used for post denitrification in a moving bed system. The carbon needed for denitrification will be provided by means of sludge hydrolysis and the use of an external carbon source.
Technical solutions for upgrading high rate and medium loaded activated sludge plants for nutrient removal
Authors: Chudoba P. , Pujol R.
Published: May 2018

In order to meet the requirements for total nitrogen removal in sensitive area, as specified by the EC Standards, existing high-rate or medium loaded activated sludge plants treating only carbonaceous pollution have to be upgraded. Two attractive technical solutions are proposed. Depending on both the design and operational conditions of the activated sludge plants, all existing treatment facilities will be reused for nutrient removal with either an immobilized nitrifying system implemented directly in the existing activated sludge tank or with an additional up-flow nitrifying biofilter. Both technical solutions enable the effluent total nitrogen concentration to be as low as 10 mg TN/l. When a high or medium loaded activated sludge plant with primary settling tanks is designed for a HRT of more than five hours, the Pegazur immobilized carrier system can be implemented directly in the biological reactors. The existing aeration tank is divided into anoxic and aerated zones, and the nitrifying Biocubes are introduced in the aerated one. Such an upgraded activated sludge system (which did not nitrify before the upgrading) can reach a maximum eliminated loading rate of 0.5 kg NH4–N per m3 of aerated volume per day at 12°C. This solution was used to upgrade the 120,000 p.e. Bellozanne Sewage Treatment Works, Jersey, Channel Islands, UK. When an existing high rate activated sludge plant is designed for a HRT of less than five hours, the activated sludge tank can be transformed into a high-rate denitrifying anoxic reactor, coupled to a nitrifying Biofor up-flow filter. The high-rate anoxic sludge is continuously controlled by an ORP probe in order to ensure both the denitrifying conditions and recycle ratios are at their optimum level. This controlled operation and high water velocities applied to the nitrifying up-flow Biofor enable the operational mode to switch from dry weather conditions to wet weather conditions where the recycle of nitrified liquor is switched off and the high loaded anoxic sludge is temprarily aerated.
New German design guideline for single stage activated sludge plants
Authors: Kayser R.
Published: May 2018

The German design guideline A 131 “Design of single stage activated sludge plants” was amended in 1999. The main changes of the guideline from 1991 are outlined. The design procedure for plants with nitrogen and phosphorus removal is presented.
Modelling and test of aeration tank settling (ATS)
Authors: Nielsen M.K. , Bechmann H. , Henze M.
Published: May 2018

The use of aeration tank settling during high hydraulic loads on large wastewater treatment plants has previously been demonstrated as a reliable technique and proven valuable. The paper proposes a simplified deterministic model to predict the efficiency of the method. It is shown that a qualitatively correct model can be established. The simplicity of the model allows for on-line identification of the necessary parameters, so that no maintenance is needed to use of the on-line model for control.

The practical implementation on three plants indicates that implementation of STAR with ATS control gives 50% increase of plant capacity for 3% extra cost.
Assessment of organic constituents in sewage sludge
Authors: Litz N.
Published: May 2018

A standardized evaluation concept based on human toxicity, ecotoxicity and soil related data has been developed for the assessment of pollutants in sewage sludge. This assessment concept for different compounds is applicable using evaluation steps that are comparable and transparent based on a classification system. All compounds assessed here were assigned to three groups: pollutants of primary relevance, pollutants of secondary relevance and such, on which more information is necessary for evaluation. For the purpose of comparing the evaluation concept with results from some investigations under field and laboratory conditions degradation, sorption, retardation and plant transfer data for LAS are presented and discussed.
Activated sludge population dynamics and wastewater treatment plant design and operation
Authors: Wanner J. , Ruzickova I. , Krhutkova O. , Pribyl M.
Published: May 2018

The development and tasks of IAWQ specialist group on Activated Sludge Population Dynamics have been briefly described. The paper is aimed at three main topics of population dynamics, i.e., competition of nitrifying and organotrophic bacteria, population dynamics of enhanced biological phosphate removal, and activated sludge bulking and foaming. The population dynamics problems are illustrated on examples of Czech activated sludge plants. The examples were selected from a large national survey of activated sludge plants accomplished in 1995–1999. Nitrification proved to be the most difficult process to design and control in nutrient removal activated sludge systems. The survey of enhanced biological phosphate removal processes has shown that the arrangements used in the Czech Republic support well this process. The competition of PAOs with “G” bacteria in full-scale plants is less common than could be expected from previous laboratory studies. The phenomenon of anoxic phosphate uptake was also observed in full-scale plants. Traditional activated sludge separation problem of bulking was observed with much less frequency than expected. On the other hand, foaming caused by M. parvicella, N. limicola and by GALOs has become the most serious operation problem. The survey has also shown that physical rather than biological methods of foaming control are successfully applied in Czech activated sludge plants. The extent of foaming problems underlines the importance of a proper design and construction of final clarifiers.
Performance of the biological nitrogen and phosphorus removal in four large WWTPs in Germany
Authors: Rosenwinkel K.-H. , Obenaus F. , Wichern M.
Published: May 2018

In this paper the design data, flow sheets, operating results and running experiences of four municipal wastewater treatment plants are presented. The size of these plants varies between 95,000 and 830,000 people equivalents. Different activated sludge systems running with cascades and simultaneous nitrification/denitrification are practised in these plants. The data of these different plants are compared.
Aerobic treatment of industrial waste water – experiences with the dosage of nitrogen and phosphorus
Authors: Prendl L. , Nikolavcic B.
Published: May 2018

In industrial wastewater, especially from food industry, the concentrations of the organic compounds are usually high, whereas the contents of nitrogen and phosphorus are often low. For the aerobic treatment, the addition of nutrients to the industrial wastewater can be required. For ecological and economic reasons, this nutrient addition must be kept to a minimum. Unintentional nitrification and denitrification lead to an additional demand of nitrogen and should therefore be avoided at such plants. Observations from two treatment plants (50 000 m3/d, 40 t COD/d) proved that the nitrogen dosage can be controlled by monitoring the ammonia concentration. If the control procedure also considers the N/COD ratio in the raw wastewater (including the N dosage) and the organic sludge load of the last couple of days, very low effluent concentrations (NH4–N in the range of 0.3–0.5 mg/l) can be achieved and the nitrogen dosage is low. If there are periods with nitrogen in excess, too, a minimum nitrification capacity has to be maintained by means of nitrogen addition in periods of deficiency. A control procedure for phosphorus addition is to keep a fixed P/COD-ratio in the raw wastewater (including P dosage). The PO4–P concentration is monitored in order to limit the maximum phosphorus dosage. Following this procedure, considerable savings of phosphorus have been achieved, keeping very low effluent concentrations (average Total-P<0.3 mg/l).
Emissions of chlorinated aromatics during sludge combustion
Authors: Samaras P. , Blumenstock M. , Schramm K.-W. , Kettrup A.
Published: May 2018

The emissions of the toxic chlorinated dioxins and furans during the combustion of sewage sludge and their distribution to the gas/solid phase were examined in this work. Sewage sludge samples were collected from two municipal and one industrial wastewater treatment plant, and were incinerated in a lab scale reactor at 1000°C. High PCDD/F emissions, about 300 ng I-TEQ/kg of fuel were observed during the combustion of the industrial sewage sludge due to the high chlorine and copper content in this sample. Co-combustion of the industrial sludge with coal resulted in reduced toxic emissions reaching up to 158 ng/kg fuel. Almost similar PCDD/F concentrations were measured in the solid particles removed at the quartz wool filter and in the gas phase. The examination of the homologue patterns revealed the domination of furans over dioxins in both the gas and the solid phase. The tetrachlorinated congeners prevailed over the other isomers in the gas phase, while in the solid phase the lower chlorinated isomers with four and five chlorine atoms dominated.
Nitrogen removal from wastewater of the chemical company Duslo
Authors: Buday J. , Halász L. , Drtil M. , Bodík I. , Németh P. , Buday M.
Published: May 2018

The results of laboratory scale modelling and real scale performance of the pre- and post-denitrification of a wastewater from the production of industrial fertilizers, pesticides and rubber additives are presented. As a substrate for the pre-denitrification, the biologically degradable organic compounds present in the influent were used. Selected wastewaters from chemical industry were used as a substrate for the post-denitrification. The results of the laboratory scale research of the pre-denitrification were successfully verified in real scale, an efficiency of 97% and 88% was reached for the removal of NO2––N and NO3––N respectively. The efficiency of the post-denitrification in real scale was 15% from the entering amount of NOx––N (NO2––NO3––N). Pre-denitrification removed about 190 kg NOx––N and post-denitrification about 85 kg NOx––N daily.
Thermophilic process and enhancement of excess activated sludge degradability – two ways of intensification of sludge treatment in the Prague central wastewater treatment plant
Authors: Zábranská J. , Dohányos M. , Jenícek P. , Kutil J.
Published: May 2018

The paper describes two ways of intensification of sludge treatment in the Prague Central Wastewater Treatment Plant: full-scale experiment with thermophilic anaerobic digestion and full-scale experiment with lysis thickening centrifuge.

Increasing temperature from the mesophilic to thermophilic level in the full-scale digesters leads to a better utilization of the existing facilities and consequently avoids digester overloading. The higher degradation efficiency is associated with higher biogas production and improvement of the energy balance of the process. Due to a careful and slow increasing of the operating temperature the thermophilic process was very stable.

The partial destruction of excess activated sludge cells during the thickening by means of a lysis-thickening centrifuge produces cell lysate. The presence of the cell lysate in thickened excess activated sludge causes a substantial increment in the methane yield and the biodegradability of thickened activated sludge in comparison with untreated excess sludge. The improvement of methane yield from thickened activated sludge was on average 11.5–31.3% dependent on the sludge quality. The operation of lysis-thickening centrifuges in the Prague Central Wastewater Treatment Plant proved the possibility of full-scale application of the disintegration method.
The cost of municipal sewage treatment – structure, origin, minimization – methods of fair cost comparison and allocation
Authors: Bode H. , Grünebaum T.
Published: May 2018

Cost comparison in the field of wastewater treatment is a difficult task, particularly concerning sewages charges in different countries. German wastewater management is, for one thing, known to be very efficient, yet, for another, comparatively costly on an international scale. In this context, the marginal conditions typically prevailing in the field of sewage treatment in Germany should be mentioned: dense population and industrialization with high export-oriented production rates, high-profile purification requirements enforced by law. To establish a valid cost comparison, it is necessary to include both the investment and the operating expenses within the scope of the overall annual costs. The major factors impacting the different cost types are represented. Only if these factors are taken into account and quantified, will cost comparison be fair and lead to useful results. Ten hints for cost minimization are given to serve as a guideline for successful and responsable cost reduction. Cost transparency is the prerequisite for the possibility to develop saving potentials while simultaneously securing the social and political acceptance of the charges levied, and to compare the different plants with one another. Experience from Ruhrverband, a water management association for an entire catchment area, being responsible for planning, building and operation of 94 wastewater treatment plants and other plants for water quantity and water quality management, is reported.
Simultaneous removal of nitrogen and phosphorus in a two-biofilter system
Authors: Pak D. , Chang W.
Published: May 2018

A two-biofilter system operated under alternate conditions of anaerobic/aerobic was tested to simultaneously remove nitrogen and phosphorus from sewage. The factors affecting simultaneous removal of nitrogen and phosphorus by the two-biofilter system were investigated. Those factors appeared to be influent COD/T-N and COD/T-P ratio, nitrogen loading rate and hydraulic retention time. Nitrite and nitrate produced in the biofilter in aerobic condition affected phosphorus removal by the two-biofilter system. The amount of biomass wasted during the backwash procedure also affected total nitrogen and phosphorus removal by the system.
Performance of an anaerobic baffled reactor (ABR) as a hydrolysis-acidogenesis unit in treating landfill leachate mixed with municipal sewage
Authors: Wang B. , Shen Y.
Published: May 2018

A study on the performance of an Anaerobic Baffled Reactor(ABR) as a hydrolysis-acidogenesis unit in treating the mixed wastewater of landfill leachate and municipal sewage in different volumetric ratios was carried out. The results showed that ABR substantially improved the biological treatability of the mixed wastewater by increasing its BOD5/COD ratio to 0.4–0.6 from the initial values of 0.15–0.3. The formation of bar-shaped granular sludge of 0.5–5 mm both in diameter and length with an SVI of 7.5–14.2 ml/g was observed in all compartments of the ABR when the organic loading rate reached 4.71 kgCOD/m3 · d. The effects of the ratios of NH4+-N/COD and COD/TP in mixed wastewater on the operational performance were also studied, from which it was found that a reasonable NH4+-N/COD ratio should be lower than 0.02, and the phosphorus supplement was needed when the volumetric ratio was higher than 4:6 for stable operation of ABR.
Comparative study of oil accumulation characteristics in attached and suspended growth reactors
Authors: Abadi Y. , Galil N.
Published: May 2018

In this study, the sorption extent and characteristics of low biodegradability hydrocarbons to biomass in attached growth (AG) and suspended growth (SG) processes were compared. Distinction was made between settled biomass from the settling chamber (sludge biomass) and non-settled biomass from the process effluent (effluent biomass). In both processes the sorption to the sludge biomass was the main oil removal mechanism, however, differences in the extent and characteristics of oil sorption were observed. The AG sludge biomass sorbed more oil than the SG sludge biomass and the sludge biomass oil fraction was always higher than the effluent biomass oil fraction. In the SG process, the sludge biomass oil fraction was lower than the effluent biomass oil fraction for the first 42 days of operation and then the trend reversed.

The settling quality in the SG process was damaged during the sorption of oil and biomass concentration in the reactor decreased, while the AG process suffered only from short-term disturbances in the settling quality. Furthermore, the results indicated that effluent suspended solid concentration in the AG process decreased when the oil sorption rate was high.
Palestinian participation in efforts towards regional cooperation in the water sector
Authors: Assaf K.
Published: May 2018

The Palestinian Water Authority (PWA) has adopted several key elements as a water policy to be used as a basis for all decisions within the water and wastewater sectors. In addition, a water management strategy has been developed which includes the key strategy of “promoting regional and international cooperation”. The Palestinian National Authority is a Core Party Member of the Multilateral Working Group on Water Resources within the Peace Process agenda. Under this framework, the PWA is participating in several projects that not only have a national focus, but also a regional focus in order to promote a factual basis for regional cooperation in the water sector. This presentation will outline the ongoing projects in the multilateral framework pointing out the regional significance for each project and emphasizing the importance of building strong professional and technical liaisons in the water sector.
Towards sustainable development in the water sector: a perspective from Palestine
Authors: Daibes F.
Published: May 2018

The water sector in Palestine suffers from great damage and serious institutional fragmentation. The deterioration in the water services and the inadequate coverage at the different levels are two major weaknesses in the sector. Adding to that, the responsibilities are scattered among relevant institutions and unclear. Aiming at facing the challenges and obstacles, and in order to approach the achievement of sustainable development in the water sector, the Palestinian Authority (PA) had to take certain measures and actions. The elements of a “National Water Policy” have been adopted that aim at sustaining the resource. However, a set of measures and regulations in line with the policies still has to be issued and enforced. A central independent authority, the Palestinian Authority, was established in order to execute the National Water Policy. The main aims of this authority as a regulator will be represented. This fairly new approach for managing water resources in Palestine is time consuming and requires a big change in the national culture. Public awareness and stakeholder participation are vital strategies to create incentives for public commitment and involvement.
Determination of the optimum loading strategies for monochloro-, trichloro-, and 2,4-dichlorophenoxyacetic acids to anaerobic cultures
Authors: Guven E. , Erguder T.H. , Demirer G.N.
Published: May 2018

With respect to their adverse health and environmental effects, halogenated organic compounds (HOCs) are among the most important priority pollutants. HOCs cannot be easily biodegraded. However, if suitable microbial cultures are acclimated to these compounds properly, and the optimum operating conditions are achieved, HOCs can be removed with biological methods. Recently, great interest has focused on reductive anaerobic dehalogenation for the removal of these compounds. This process yields lower halogenated compounds which are less toxic and more amenable to further biodegradation. Chloroacetic (CAA), trichloroacetic (TCAA), and 2,4-dichlorophenoxyacetic acids (2,4-D) are significant industrial compounds mainly usedin herbicide, pesticide, and dye manufacturing. The objective of this study was to: (i) investigate the inhibitory effects of CAA, TCAA, and 2,4-D; and (ii) determine the optimum loading strategy of these HOCs to anaerobic cultures. To this purpose Anaerobic Toxicity Assay (ATA) and Optimum Loading Strategy experiments were conducted for CAA, TCAA, and 2,4-D. The results of this study are expected to develop an optimum loading strategy of HOCs to anaerobic systems and contribute to more effective use of anaerobic reductive dehalogenation of HOCs.
Infrastructure development after Oslo B in the West Bank governates of the Palestinian National Authority
Authors: Ja'as M.
Published: May 2018

Water and wastewater infrastructure was either nonexistent or in a state of deterioration at the time of the establishment of the Palestinian Water Authority. Despite the lack of sufficient water supplies, the Palestinian Water Authority has been working to deliver new water supplies to unserved areas and at the same time is pushing a program of rehabilitation in order to reduce the quantities of either lost or unmetered water. A presentation will be made of the immediate needs of the Palestinian Water Authority for Palestinians in the West Bank districts. A summary will be made of the unserved towns and villages, of the ongoing rehabilitation projects, and a brief outline of the larger packaged projects that should be completed in the next couple of years. As a conclusion, a review will be made ofArticle 40 of Oslo B illustrating the status of the delivery of “allocated” water quantities during this “interim period” before the final status negotiations, where the rights of the Palestinians in the water resources of the region will be detailed.