bluuebunny/crossref_metadata_2025 huggingface dataset:
Removal of bacteria in subsurface flow wetlands
Authors: Green M. B. , Griffin P. , Seabridge J. K. , Dhobie D.
Published: May 2018

Removal of E. coli and total coliforms in subsurface flow constructed wetlands is investigated in field surveys and pilot experiments. Both systems use reed beds with 5-10 mm gravel medium receiving secondary effluents. A diurnal pattern of numbers was indicated in the survey of an operational tertiary reed bed at Leek Wootton. Removals of E. coli and total coliforms were compared in dry and wet periods in surveys on two successive years. Removals of about 1.5 to 2.1 log were found in dry weather. Removals fell in wet weather although no change was detected in removal of BOD5, TSS and amm N.

The effect of different flow rates was compared using a pilot reed bed. A trend of increasing removal was seen between retention times of 12, 24, 48 and 120 hrs but variation between samples implied caution. All effluent samples from the pilot had less than 1000 cfu E. coli/100 ml at retention times of 24 hrs or more.
Deterministic and stochastic aspects of constructed wetland performance and design
Authors: Kadlec Robert H.
Published: May 2018

Potato processing wastewater contains high concentrations of COD, TSS and TKN. A combination of surface flow wetlands, intermittent vertical flow wetlands, ponds and land application has been used for treatment. This engineered natural system balances irrigation requirements, nitrogen supply and seasonal growth patterns to provide effective year-round operation. A first pilot wetland was operated to determine operability, effectiveness, and plant survival at high COD and nitrogen concentrations. A second pilot system of four wetlands in series was operated to obtain design and operating information. Two surface flow wetlands provided TSS and COD reduction, and ammonified the organic nitrogen. Subsequently, nitrification occurred in the vertical flow wetlands, followed by denitrification in a surface flow wetland. The design target was a balanced nitrogen and irrigation supply for application to crops. Winter storage as used to match the crop application period to the growing season. Both pilot projects met design objectives, and a full scale system has begun operation.
Hydraulic tracer studies in a pilot scale subsurface flow constructed wetland
Authors: King Andrew C. , Mitchell Cynthia A. , Howes Tony
Published: May 2018

Current design procedures for Subsurface Flow (SSF) Wetlands are based on the simplifying assumptions of plug flow and first order decay of pollutants. These design procedures do yield functional wetlands but result in over-design and inadequate descriptions of the pollutant removal mechanisms which occur within them. Even though these deficiencies are often noted, few authors have attempted to improve modelling of either flow or pollutant removal in such systems.

Consequently the Oxley Creek Wetland, a pilot scale SSF wetland designed to enable rigorous monitoring, has recently been constructed in Brisbane, Australia. Tracer studies have been carried out in order to determine the hydraulics of this wetland prior to commissioning it with settled sewage. The tracer studies will continue during the wetland's commissioning and operational phases. These studies will improve our understanding of the hydraulics of newly built SSF wetlands and the changes brought on by operational factors such as biological films and wetland plant root structures.

Results to date indicate that the flow through the gravel beds is not uniform and cannot be adequately modelled by a single parameter, plug flow with dispersion, model. We have developed a multiparameter model, incorporating four plug flow reactors, which provides a better approximation of our experimental data. With further development this model will allow improvements to current SSF wetland design procedures and operational strategies, and will underpin investigations into the pollutant removal mechanisms at the Oxley Creek Wetland.
A heuristic approach algorithm for the optimization of water distribution networks
Authors: Lin Bi Liang , Wu Ray Shyan , Liaw Shu Liang
Published: May 2018

Many optimization models to determine cost-effectiveness and obtain the least-cost system designs for water distribution networks have been developed. An algorithm used for solving an optimization model, such as the branch-and-bound or enumeration method, has deficiencies that may include efficiency problems and local optimal solution problems. A heuristic approach, with a bounded implicit enumeration (BIE) algorithm was developed in this study to improve searching efficiency. The heuristic approach first treats the system as a sub-system so that the sub-system's solution must spread widely at the solution space. Then, the optimal sub-system solution is found by a BIE algorithm. On the basis of the optimal solution for the initial system, one larger than and one smaller than its commercial diameter is used to form a new system design. Finally, an optimal solution is determined by using the BIE algorithm until the same solution is found. In this study, five water distribution network designs were used to illustrate the performance of this approach. The results show that a heuristic approach is more efficient than the BIE alone. The efficiency becomes more obvious when the system becomes larger. Comparing the three case studies, the heuristic approach along with the BIE algorithm finds global optimal solution more efficiently.
An interactive inexact-fuzzy approach for multiobjective planning of water resource systems
Authors: Wu S. M. , Huang G. H. , Guo H. C.
Published: May 2018

In this study, an inexact fuzzy multiobjective programming (IFMOP) method is developed and applied to a case study of water pollution control planning in the Lake Erhai Basin. The IFMOP improves upon the existing multiobjective programming methods with advantages in data availability, solution algorithm, computational requirement and result interpretation. The case study project was supported by the United Nations Environment Programme (UNEP). The results indicate that desired schemes for a number of system activities in different subareas/periods were obtained. Inheriting uncertain natures of the model inputs, the majority of solutions present as inexact values which provide decision-makers with a flexible decision space. Generally, the modeling results would provide scientific bases for the formulation of policies/strategies regarding regional socio-economic development and environmental protection.
Modelling of oxidation ditches using an open channel flow 1-D advection-dispersion equation and ASM1 process description
Authors: Stamou Anastasios I.
Published: May 2018

A river water quality model is presented for the prediction of the concentration fields of the water quality variables in an oxidation ditch performing carbon oxidation, nitrification and denitrification. The model involves the one-dimensional convection-dispersion equations for all the variables, which are described in the IAWPRC Activated Sludge Model No 1. The model is applied to a typical oxidation ditch to show that all variables, with the exception of DO, are uniformly distributed in the ditch; thus permitting the characterisation of the oxidation ditch as a completely mixed reactor. The DO concentration, which controls the reaction rates of almost all the processes, shows a plug flow behaviour. The potential of the present model to be used to improve the DO control system of the ditch and to perform real time predictions is also demonstrated. All calculations have been performed with a PC.
The application of the root zone method for the treatment and reuse of high-strength abattoir waste in Mexico
Authors: Rivera Fermin , Warren Alan , Curds Colin R. , Robles Esperanza , Gutierrez Alejandro , Gallegos Elvia , Calderón Arturo
Published: May 2018

A two-stage system for treating high-strength wastewater from an abattoir at Pachuca, Mexico is described. The system consists of an anaerobic digester followed by an artificially-constructed wetland which employs horizontal subsurface flow through the root zone of emergent hydrophytes planted in a gravel substrate. The main goals of this study were to monitor the treatment efficiency of the system for the first twelve months of operation and to assess the suitability of the effluent for irrigation purposes. The treatment efficiency during the twelve month period was generally good with mean removal efficiencies of 88.5% for BOD5, 87.4% COD, 89% suspended solids, 73.6% organic nitrogen and >99% faecal coliforms. Removal rates were generally poor for orthophosphates, NH3-nitrogen and NO3-nitrogen. The differing roles of the two stages in the treatment process are discussed. Although not suitable for irrigating crops, the effluent is being successfully used for the irrigation of ornamental plants and recreational lands.
Constructed wetlands for wastewater treatment in Estonia
Authors: Mander Ülo , Mauring Tõnu
Published: May 2018

In Estonia many natural/semi-natural wetlands have been used for municipal or agricultural wastewater. During the last 6 years twelve constructed wetlands for wastewater purification were established. Budgets of organic matter (BOD), total-N and total-P of three systems (a sand/plant filter with vertical flow, established in 1992, area 90 m2, loading 3.8 g BOD m−2 d−1; a combined overland flow-vertical flow root-zone system on a Phalaris arundinacea-slope, 1989, 2400 m2 ha, 1 g BOD m−2 d−1; an aquatic macrophyte channel (bioditch), 140 m2, 40 g BOD m−2 d−1), located in southern Estonia, are analyzed. Except for nitrogen, the efficiency of the sand/plant filter was found satisfactory: 82%, 36%, and 74% for BOD5, total-N, and total-P, respectively. The poor performance with respect to nitrogen may be caused by weak vegetation. In thePhalaris -system, 65% of organic matter, 67% N, and 80% P was removed. The average output concentrations of this system were always lower than the recommended limits (BOD5 <10 mg l−1, total-N <10 mg l−1, and total-P <2 mg l−1). Due to the high input load, the BOD5, total-N, and total-P values in the outlet of the bioditch were high and extremely variable: 5–100, 6–16, and 1–4 mg l−1, respectively. To guarantee the recommendable output values from the bioditch, either a significant decrease of input load or an enlargement of the area of the wetlands would be needed. All results show that compared to other seasons the winter performance was not reduced.
Identification and characterization of water quality transients using wavelet analysis. II. Application to electronic water quality data
Authors: Whitfield Paul H. , Dohan Kathleen
Published: May 2018

Two wavelet transform techniques for identifying water quality transients are applied to example data sets from two small streams. Temperature and conductance represent the range of properties from periodic processes to transient events. Both methods were successful in identifying the location, duration and magnitude of the transient events in these data sets. The methods may be refined to automate the detection and classification of transient events.
Simulation of a transient failure in a wastewater treatment plant: a case study
Authors: Rouleau Stéphane , Lessard Paul , Bellefleur Didier
Published: May 2018

Very few case studies of treatment plant model calibration with field data have been reported in the literature, and none with data collected during rain events and showing sludge blanket overflows. The objective of this paper is thus to present the results of an evaluation exercise done with data collected through intensive sampling during rain events. The results show that it is possible to simulate the behaviour of a plant during a wet weather period with the usual models found in the literature.
Small wastewater treatment plants - a challenge to wastewater engineers
Authors: Boller Markus
Published: May 2018

Three conferences on “Small Wastewater Treatment Plants” organized by the IAWQ Specialist Group demonstrate worldwide interest and activities in this matter and the need to exchange experience concerning planning, design, construction, operation, maintenance and control of small treatment plants. In near future, the number of small treatment works will increase tremendously and will be accompanied by a strong demand for information on appropriate procedures and technologies. Pollution problems caused by small wastewater flows are usually restricted to small areas, however, in view of the high per capita costs, treatment requirements and alternatives have to be studied carefully. In comparison to larger plants, more pronounced and different boundary conditions such as load fluctuations, operation and maintenance problems, per capita costs, and a large variety of feasible treatment and disposal systems ask for experienced engineers with a broad and sound knowledge in rural water quality management. The technical alternatives reaching from mechanical and simple biological low rate systems such as ponds, sand filters and reed beds to complex high rate suspended and fixed biomass reactors have to be evaluated regarding plant size, operation safety, reliability, demand for skilled personnel, investment and operation costs. In this respect, water engineers are increasingly challenged, not only to deal with a broad range of present and future treatment technologies, but also to integrate economical and social aspects into their evaluations.
Removal of rate-limiting organic substances in a hybrid biological reactor
Authors: Guang Hao Chen , Ju-Chang Huang , Lo Irene M. C.
Published: May 2018

This paper is aimed at investigating the removal of both easily as well as slowly biodegradable (or rate-limiting) organic substances in an aerobic hybrid reactor which consists of both the suspended and attached biomass (or biofilm). The study involves theoretical computer simulations on the reactor performance. It has been shown that the organic removal efficiency in a purely suspended growth system decreases markedly when the maximum specific removal rate (MSRR) of an organic substance is lower than 0.5/day. Thus, a suspended growth system is not effective in removing any substance of low biodegradability. On the contrary, when a hybrid system is applied, a rate-limiting organic substance with an MSRR of 0.1/day can still be effectively removed as long as the weight ratio of the biofilm to the suspended biomass is not less than 0.027. In such a system, an increase in the amount of the suspended biomass will not significantly increase the removal rate for such a substance because a slowly biodegradable substance needs some specific types of microorganisms which have a low growth rate. As such, in a biofilm system it is easier to maintain these microorganisms than in a suspended growth reactor. In this case, an increase of biofilm will improve the treatment efficiency. For the removal of an easily biodegradable substance (i.e., MSRR is not less than 0.5/day), the suspended biomass plays a more important role than the fixed biomass in a hybrid reactor. Through simulation modelling, it is known that to obtain 80% or more removal of a slowly biodegradable substance (MSRR at 0.1/day) in a hybrid reactor, the optimal operating values of organic loading rate, hydraulic retention time, and the ratio of support surface to reactor volume are 0.53 kg COD/m3/day, 6 hours, and 225 m2/m3, respectively. The results of this study suggest that to achieve an effective simultaneous removal of both easily and slowly biodegradable organics a hybrid reactor offers the best solution.
Effect of biosorption on the damping of influent fluctuation in activated sludge aeration tanks
Authors: Fujie Koichi , Hu Hong-Ying , Lim Byung-Ran , Xia Huang
Published: May 2018

To describe the organic removal performance in an activated sludge process, the effect of biological adsorption (biosorption, hereinafter) of both soluble and particulate organic substances (SOS and POS, respectively, hereinafter) on the rate of organic removal must be taken into account. This study quantitatively investigated the biosorption of organic pollutants in the domestic wastewater by the activated sludge. The capability of biosorption and the rate of bio-oxidation of organic pollutants were formulated based on the experimental results as functions of both COD concentration and temperature. The biosorption capacity of activated sludge was proportional to COD concentration in the mixed liquor originated from the influent. The kinetic expressions were combined with the equation of longitudinal liquid mixing to set up the mathematical model to predict the effluent COD, and thus to clarify the effect of biosorption on the damping of influent fluctuations of both COD concentration and the inflow rate. The model was also successfully applied to assessing the effectiveness of MLSS control strategies in equalizing the effluent water quality.
Biosorption of cadmium by algal biomass: adsorption and desorption characteristics
Authors: Chu K. H. , Hashim M. A. , Phang S. M. , Samuel V. B.
Published: May 2018

The adsorption and desorption characteristics of a biosorption process comprising the biomass of the marine alga Sargassum baccularia, cadmium ions and desorbing agents hydrochloric acid and ethylenediaminetetraacetic acid (EDTA) were investigated using a batch reactor system. Both desorbents were effective in stripping adsorbed cadmium from the biomass. It was found that HCl at pH 2 could desorb 80% of the cadmium initially loaded onto the biomass. Almost complete recovery of cadmium was achieved by a 3.24 mM EDTA solution. The reusability of the biomass was tested in five consecutive adsorption-desorption cycles. The quantity of cadmium desorbed over the five cycles with either HCl or EDTA as desorbent corresponded well to the quantity loaded, indicating that complete desorption was readily achieved. However, the cadmium uptake capacity of the biomass deteriorated with repeated use of HCl or EDTA. HCl was found to have reduced cadmium uptake by 56% while the reduction for EDTA was nearly 40% over the five adsorption-desorption cycles. EDTA thus emerged as a slightly better desorbing agent compared with HCl. After completion of the five cycles it was found that 30% of the original biomass weight had been lost with HCl as the desorbent. EDTA exhibited desorption behaviour similar to that of HCl by causing a biomass loss of 16%. The loss of biomass indicates that some dissolution of biomass components containing cadmium binding sites apparently occurred, reducing the cadmium uptake capacity of the biomass in multiple cycles of adsorption-desorption.
Adsorption of cadmium(II) from aqueous solution onto activated carbon
Authors: Leyva-Ramos R. , Rangel-Mendez J. R. , Mendoza-Barron J. , Fuentes-Rubio L. , Guerrero-Coronado R. M.
Published: May 2018

The adsorption isotherm of cadmium on activated carbon was measured in a batch adsorber. Effects of temperature and solution pH on the adsorption isotherm were investigated by determining the adsorption isotherm at temperatures of 10, 25, and 40°C and at initial pH values from 2 to 8. Langmuir isotherm better fitted the experimental data since the average percent deviation was lower than with the Freundlich isotherm It was noticed that the amount of Cd2+ adsorbed was reduced about 3 times by increasing the temperature from 10 to 40°C. It was found that Cd2+ was not adsorbed on activated carbon at pH of 2 or lower and that Cd2+ was precipitated out as Cd(OH)2 at pH values above 9. Maximum adsorption capacity was observed at pH of 8 and the adsorption capacity was decreased about 12 times by reducing the initial pH from 8 to 3. According to the cadmium speciation diagram the predominant species below pH of 8 is Cd2+. Thus, cadmium was adsorbed on the activated carbon surface as Cd2+. It was concluded that the adsorption capacity is a strong function of pH and temperature.
Pilot plant study on ozonation and biological activated carbon process for drinking water treatment
Authors: Kim Woo Hang , Nishijima Wataru , Shoto Eiji , Okada Mitsumasa
Published: May 2018

A study on advanced drinking water treatment was conducted in a pilot scale plant taking raw water from Minaga Reservoir, Japan. Ozonation-biological activated carbon process (O3-BAC), BAC process (BAC) and chlorination-granular activated carbon adsorption process (Cl2-GAC) were evaluated based on the following parameters; dissolved organic carbon (DOC), adsorbable DOC (ADOC) and biodegradable DOC (BDOC). The raw water used was pre-treated by biofiltration for suspended solid removal and biological treatment. Contact time for ozonation and chlorination was 24 min. Empty bed contact time of activated carbon column was 15 min. Ozone dosage was 3 mg • 1−1. Chlorination was carried out to maintain a residual chlorine concentration of 0.2 mg • 1−1. Effluent DOC from biofiltration consisted of mainly ADOC (90%) and BDOC (10%). Therefore, DOC was mainly removed by adsorption in all processes. However, biodegradable DOC increased by 20% after ozonation in O3-BAC and was removed effectively by the attached bacteria on the activated carbon. Significant differences in DOC removal were not noted among the three processes during 8 months of operation. After the saturation of activated carbon, the effluent DOC from the O3-BAC was lower than that from BAC and Cl2-GAC. Ozonation improved biodegradability of organic substances and effluent water quality by the following biodegradation of biodegradable DOC by biological activated carbon.
Role of inorganic phosphorus in controlling regrowth in water distribution system
Authors: Sathasivan A. , Ohgaki S. , Yamamoto K. , Kamiko N.
Published: May 2018

Conventionally organic carbon is assumed to be the limiting nutrient of regrowth. Inorganic phosphorus in comparison to carbon should be a good candidate for regrowth control because it can be measured and controlled. It may be able to limit regrowth in drinking water distribution systems. In order to clarify whether inorganic phosphorus can really control or limit regrowth, three kinds of bioassays were performed: 1. for different combinations of acetate, phosphorus, and other inorganic nutrients added to different test tubes containing pure water, 2. for different tap water dilutions with pure water, and 3. for different phosphorus addition to test tubes containing all nutrients but phosphorus. The inoculum used was taken from a drinking water distribution system carrying chlorinated groundwater. Results indicated the following: 1. tap water bacteria cannot grow on simple organic carbon source (acetate) alone, 2. not organic carbon but inorganic nutrients limited the growth in tap water, and 3. tap water bacterial growth was suppressed when phosphorus was not present and it was not affected by over-presence of phosphorus when carbon or other nutrients became limiting. This gave a clue that phosphorus might play a major role in controlling regrowth in drinking water distribution system.
Water treatment plant residuals management
Authors: Dharmappa H. B. , Hasia A. , Hagare P.
Published: May 2018

Water treatment plants produce enormous amounts of sludge. Due to increased environmental concern, recently, there is considerable amount of pressure on the water authorities for the safe disposal of the sludge. Currently, the most acceptable form of disposal is sanitary landfilling, which requires sludge to be dewatered to 20-40% of solids. One of the most commonly used dewatering techniques is sand drying beds. This process is popular because of its reliability, ease of use and low cost. However, one of the basic concerns with this process is the requirement of a large area of land. This could be overcome by chemical conditioning of the sludge, which can accelerate the dewatering rate substantially. At this stage, however, there are no guidelines for the design of the sand drying beds for treating chemically conditioned sludges.

This study is conducted to investigate the design and performance of sand drying beds for treating chemically conditioned water treatment plant (WTP) sludge. Experiments are conducted using laboratory scale sand drainage columns. The results indicate that the drainage rates, after adding polymer, increased by 9 times for clarifier sludge and 20-25 times for filter backwash sludge. Thus, the land area requirement for sand drainage bed can be drastically reduced through polymer addition. Optimal dose of polymer is found to be between 3 and 6 kg/t of dry solids, with dilute sludges requiring high dosages. The cake solids concentration increased from 3 to 12% as the polymer dose increased from 0 to 16 kg/t of dry solids. The variation of drainage rates and cake solids with solids/hydraulic loading rates are found to vary depending on the type of sludges and polymers. The filtrate quality is found to be independent of polymer dose and solids loading rates.
Total organic carbon as a predictor of biological wastewater treatment efficiency and kinetic reaction rates
Authors: Wilson Francis
Published: May 2018

The study investigated the use of Total Organic Carbon (TOC) to predict the efficiency of removal of a high strength wastewater and to obtain information about the kinetic processes in the rotating biological contactor system. For the determination of efficiency of removal, standard TOC analysis was used, and the results compared with those of the more usual BOD and COD tests. For the determination of the order of reaction, TOC alone was used. The results indicated that, for the high strength food processing wastewater being treated, the use of TOC gave excellent correlations between efficiency of removal and input parameters such as initial concentration, hydraulic loading rate and applied organic loading rate. The use of TOC also gave very high statistical correlations leading to an overall value for the order of reaction for the rotating biological contactor which agreed with previous research results. However, the value obtained for the order of the reaction was very dependent on the values of the input parameters which partly could be construed as showing evidence for the change from approximately first order to near zero order of reaction depending upon the input parameters.
Simultaneous COD removal and denitrification of wastewater by bio-electro reactors
Authors: Kuroda M. , Watanabe T. , Umedu Y.
Published: May 2018

Application of a bio-electro reactor process for the treatment of wastewater containing nitrate and internal source of hydrogen donor as organic matter was experimentally investigated. The bio-electro reactor consisted of immobilized denitrifying bacteria electrode as cathode and carbon electrode as anode. Hydrogen gas was produced on the cathode surface by the electrolysis of water when electric current was applied, and immediately utilized to reduce biologically nitrate to nitrogen gas by the cathodic immobilized denitrifying bacteria. Consumption characteristics of organic matter and utilization of hydrogen gas derived from the electrolysis of water for denitrification was studied by batch experiments. Continuous treatment experiments using a synthetic wastewater containing nitrate and organic matter were carried out to investigate the denitrification and organic matter removal performances. Denitrification occurred with simultaneous utilization of organic matter existed as internal source of hydrogen donor in the wastewater and hydrogen gas by electrolysis of water. Hydrogen gas was utilized efficiently for denitrification even if excess amount of organic hydrogen donor existed in wastewater. In this bio-electro reactor system, it was confirmed that COD as well as nitrate was removed simultaneously by applied electric current in continuous experiment, though further investigation are necessary to analyze the COD removal by applied electric current in detail.
Influence of sulfur compounds and heavy metals on the methanization of tannery wastewater
Authors: Shin Hang-Sik , Oh Sae-Eun , Lee Chae-Young
Published: May 2018

The main purpose of this study is to assess effects of sulfur compounds and heavy metal on the methanization of tannery wastewater containing high concentration of sulfate and chromium. The volumetric loading rates (VLR) were between 0.8 and 2.0 kgCOD/m3.d. at hydraulic retention times (HRT) of 18 to 30 h at 35°C. The COD removal efficiency was about 75% during the operation period except temperature shocks. COD removal efficiency and gas production rate decreased rapidly when the temperature dropped to 25°C. In the competition between SRB and MPB, about 13% of the removed COD was utilized by SRB at HRT of 30 h, while about 43% was used by SRB at HRT of 18 h at 35°C. Whereas, after temperature exposure to 25°C about 67% was utilized by SRB at HRT of 26 h. The results indicate that MPB is strongly suppressed by the occurrence of significant sulfate reduction since a large electron flow is distributed to the SRB. In addition, most of trivalent chromium concentration showed removal efficiency above 90%. It is considered that most of chromium concentration accumulated in the reactor probably adsorbs on the sludge or forms hydroxide precipitate.
Guiding the development of urban drainage systems by sustainability criteria
Authors: Krebs Peter , Larsen Tove A.
Published: May 2018

The development of urban drainage towards sustainability is discussed, primarily on the basis of case studies of mature urban drainage systems. Typical problems and a series of possible measures to enhance the systems performance are evaluated. We consider CSOs, receiving water quality, and decreasing ground water levels as actual problems. We distinguish between improvement strategies which focus on the technical system itself (e.g. storm water retention tanks, real time control) and strategies which may be described either as source control or as improving the resilience of the receiving water. Their efficiency is evaluated on the basis of short term ‘conventional’ criteria and by means of the following sustainability criteria: systems definition (time and space constants), resource efficiency and degrees of freedom. Surprisingly, the rating of the different strategies according to the two sets of criteria are quite close: In both cases, the measures which do not narrowly focus on the technical system obtain the better score.
Source separated urine-nutrient and heavy metal content, water saving and faecal contamination
Authors: Jönsson Håkan , Stenström Thor-Axel , Svensson Jan , Sundin Annika
Published: May 2018

Human urine is by far the largest contributor of nutrients to household wastewater. Source separation of urine can significantly decrease the nutrient load on the recipients. By recycling the urine to agriculture as a fertiliser, with very low levels of heavy metals, the nutrients are made into resources instead of becoming pollutants.

The amounts and concentrations of nutrients and heavy metals in urine solution from a source separating sewage system were measured. The concentrations of nutrients were high. The ratio of nitrogen to phosphorus was close to the expected value, indicating that the system did not have any large nitrogen loss. The heavy metal concentrations in the urine were low, much lower than that in most chemical fertilisers. Per inhabitant and day, 1.34 litres of urine solution were collected. Of this, 0.34 litres was flush water. The low flush water volume was due to the double flush mechanism of the toilets, which saved 48% of the flush water compared with conventional water closets. Per inhabitant and day, 4.9 g of nitrogen and 0.42 g of phosphorus were collected, which was 86 and 81% respectively of the expected amount. The contamination level of faecal material in the source separated urine was low.
Experiences with dry sanitation and greywater treatment in the ecovillage Toarp, Sweden
Authors: Fittschen Imke , Niemczynowicz Janusz
Published: May 2018

Experiences with dry sanitation and greywater treatment in the ecovillage Toarp, Sweden, are described, based on field studies and a survey. Technical, environmental and social issues were evaluated. The greywater was treated effectively concerning BOD7, COD, Tot-N, Tot-P and thermostable coliforms. Dry sanitation was implemented in order to recycle human excrements locally, but people's request for an environmentally sound way of life was confronted with major technical and operational problems. Composting toilets were implemented without sufficient knowledge and usage directions, resulting in partly disastrous operational results. In consequence, the majority of the ecovillage's composting toilets are now replaced by water toilets. The experiences in Toarp indicate a high demand in research activities concerning dry sanitation. Necessary research and development are described. Depending on the results, dry toilet systems might not only stay a sanitary solution in widespread areas but become a future tool to recycle human excrements.
Trends in advanced wastewater treatment
Authors: Henze Mogens
Published: May 2018

The paper examines the present trends within wastewater handling and treatment. The trend is towards the extremes, either local low-tech treatment or centralized advanced treatment plants. The composition of the wastewater will change and it will be regarded as a resource. There will be more emphasis on the sustainable aspects, on green accounting and on the health aspects.
Don't reject the idea of treating reject water
Authors: Janus Hans M. , van der Roest Helle F.
Published: May 2018

Separate treatment of sludge liquor (reject water) is a promising alternative for conventional biological extension of sewage plants with sludge digestion. Treatment of this nitrogen-rich water may significantly save in cost as well as in area demand.

This article evaluates pilot plant investigations of five treatment options: the biofilm airlift suspension reactor, the membrane bioreactor, the bioreactor without sludge retention, stripping of ammonia (both airstripping and streamstripping) and the MAP/CAFR-process. The choice of the optimal treatment method is dependent on site-specific factors. This is demonstrated by two case studies.
Reduction of nutrient emission by sludge hydrolysis
Authors: Andreasen Kjaer , Petersen Gert , Thomsen Henrik , Strube Rune
Published: May 2018

Biological sludge hydrolysis was demonstrated in full scale at three Danish wastewater treatment plants. For primary sludge the hydrolysis yield expressed in terms of filtrable COD varied from 9–16% of the total COD in the sludge (WTPs 1 & 2) and for the hydrolysis of activated sludge a yield of 2.5% of the total COD was found. The addition of hydrolysate was demonstrated to improve the biological P removal considerably. No effect on the nitrogen removal could be identified due to a favourable wastewater composition during the demonstration phase. A cost-benefit analysis showed that biological sludge hydrolysis may be a cost efficient process that should be considered in connection with the upgrading of wastewater treatment plants to nutrient removal.
Post-denitrification at the Frankfurt-Niederrad wastewater treatment plant by fluidized-bed technology
Authors: Johannes Pöpel H. , Kristeller Werner
Published: May 2018

At both two-stage activated sludge treatment plants of the city of Frankfurt an almost complete nitrification is achieved. Upgrading of the plants is required to ensure denitrification. As an alternative for implementing a solution according to the German ATV-Standard A 131 separate denitrification by an upflow fluidized-bed technology was thoroughly investigated on pilot plant scale. The results show, that a far-reaching denitrification can safely be obtained by this process. Equations for quantifying the volumetric denitrification capacity of the bed (kg ΔN/m3·d) and the effluent nitrate concentration are derived for process design. The denitrification efficiency of the system, its benefits and disadvantages are discussed together with economical aspects.
Removal of organic halogens (AOX) from municipal wastewater by powdered activated carbon (PAC)/activated sludge (AS) treatment
Authors: Bornhardt C. , Drewes J. E. , Jekel M.
Published: May 2018

The effectiveness of different treatments with powdered activated carbons (PAC) to reduce the AOX-levels in municipal wastewater was investigated in a bench-scale activated sludge (AS) treatment plant. The PAC was added either directly to the aerated basin (simultaneous PAC-treatment), or to a partial stream of clarified effluent, which was treated with PAC in an agitated tank and recirculated to the aerated basin (subsequent PAC-treatment with recirculation). The standard advanced biological treatment reduced the AOX-content by 24%. In the pilot-plant, three types of powdered activated carbons were tested for a simultaneous treatment. The treatment with 100 mg/l PICA PCO Super produced an additional reduction of AOX by 20%, whereas a dosage of 50 mg/l NORIT W-20 showed no enhancement effect, and W-35 led to an additional AOX-removal of about 9%. Also, an improved removal of DOC, NH4-N and PO4-P was observed. In all cases, the PAC addition caused a significantly improved settling of the AS, reducing the sludge-volume-index, and increasing the content of volatile solids of the PAC-sludge. In general, no evidence of a synergistic effect of the PAC addition to activated sludge, nor bioregeneration of the activated carbon, could be observed. This suggests, that the observed effects probably are caused only by simple adsorption.
The biobed® EGSB (expanded granular sludge bed) system covers shortcomings of the upflow anaerobic sludge blanket reactor in the chemical industry
Authors: Zoutberg George R. , de Been Peter
Published: May 2018

In this paper a new type of anaerobic reactor is presented. The system has been developed by Biothane Systems and is marketed under the name Biobed® EGSB reactor (Expanded Granular Sludge Bed). In this reactor it is possible to grow and maintain a granular sludge under high liquid (10 m/h) and gas velocities (7 m/h). The most striking feature is the growth of biomass in a granular form, similar to the UASB granules: no carrier material is used. The process is specially suitable to treat waste water that contains compounds that are toxic in high concentrations and that only can be degraded in low concentrations (chemical industry). An example is given for a waste water originating from a chemical factory (Caldic Europoort) in the Netherlands. In this factory formaldehyde is produced from methanol. The waste water is characterised by high concentrations of these compounds (formaldehyde to 10 g/l and methanol to 20 g/l). Due to the special configuration of the anaerobic reactor it is possible to realise a removal efficiency for both compounds of more than 98%.

It is also possible to operate the reactor as an ultra high loaded anaerobic reactor (to 30 kg COD/m3.day) for applications in other sectors of industry (e.g. brewery, yeast, sugar, corn ethanol production etc).
High-rate anaerobic wastewater treatment under psychrophilic and thermophilic conditions
Authors: van Lier Jules B. , Rebac Salih , Lettinga Gatze
Published: May 2018

Anaerobic wastewater treatment is an attractive and generally accepted technology for the treatment of various types of medium- and high-strength wastewaters. So far, this treatment technology is mostly applied at the mesophilic temperature range between 25 and 40°C. However, results of recent research conducted under both psychrophilic (< 20°C) and thermophilic (> 45°C) conditions, reveal that temperature is not a limiting factor in applying anaerobic treatment, provided the appropriate process design is chosen. Temperature has a considerable impact on various biological and physical factors of the anaerobic conversion process. For instance, the biogas production rate is reduced to a minimum at low temperatures, while it can reach extreme values under thermophilic conditions. In sludge bed systems, the biogas production rate determines the degree of mixing between the biomass and the wastewater and should, therefore, be considered in the process design. Other impacts of temperature are related to inhibition effects under thermophilic conditions and to a non-desirable accumulation of non- or partly degradable organic matter under psychrophilic conditions. Obviously, these effects may hamper the utility of the commonly applied single stage reactor systems. However, by adapting the process design to the expected prevailing conditions inside the reactor, the loading potentials and overall stability of the anaerobic high-rate process may be distinctly improved.
Sustainable technological development for urban-water cycles
Authors: van der Graaf J. H. J. M. , Meester-Broertjes H. A. , Bruggeman W. A. , Vles E. J.
Published: May 2018

Sustainable water management is a challenge for the future, as is the question what role technology may play in this. In the framework of the Netherlands interdepartmental research programme Sustainable Technological Development a pilot study has been carried out on the feasibility of a sustainable urban-water chain. Relevant unsustainability factors have been analysed to decide in what way sustainability of the water system might be increased. The starting point was a reduction by a factor of 20 for realisation in the year 2040. Relevant ideas have been processed into scenarios. In the four scenarios emphasis has been placed on reduction of emissions into the water chain, reduction of water consumption, minimal pollution (source reduction) and on small-scale. When the ideas have been realised in the ‘zero emission’ scenario, a substantial reduction of unsustainability may be realised. The attendant technological changes need to be developed.
Calculation of pressure drop in the tube flow of sewage sludges with the aid of flow curves
Authors: Proff Erwin A. , Lohmann Jürgen H.
Published: May 2018

The layout of pumps for the transport of sewage sludges in sewage plants is of great importance. The understanding of pressure drop plays a decisive role. In this paper, a method, existing in the literature, which was developed within the framework of treating the frictional behaviour of viscoelastic fluids, will be presented for the calculation of the pressure drop in pipes. Sewage sludges belong to the class of non-Newtonian fluids. They exhibit intrinsically viscous behaviour and elastic properties. Due to the variation of the viscosity across the cross-section of flow, a representative Reynolds number at the operating point of the flow is defined with the aid of a representative viscosity, in order to determine the type of flow. Exact statements about the pipe friction coefficient in laminar flow are facilitated knowing the correlations for Newtonian fluids. For the case of the turbulent region, a modified formula for Newtonian fluids is taken as a basis. The validity of the method of calculation for sewage sludge flow is compared and discussed with and with respect to numerous experiments in research plants and actual sewage plants.
Pre-treatment, measurement execution procedure and waste characteristics in the rheology of sewage sludges and the digested organic fraction of municipal solid wastes
Authors: Battistoni P.
Published: May 2018

The rheology of a wide range of sludges coming from wastewater treatment plants and from the digestion and codigestion process of sewage sludge and organic fraction of municipal solid waste (OFMSW) is measured. Sieve pre-treatment is necessary for selecting the solid fraction (<0.84 mm) in order to carry out measurement avoiding bob locking in a rotational viscosimeter. All sludges, except those from double phase digestion of source selected OFMSW, have a minimum of 80% TS and 70% TVS in this fraction. By using a plastic model, the flow curve offers a yield stress with a high standard deviation particularly at low solid content, while the rigidity coefficient s.d. is less than 10% at 90% probability. The plastic model can be proposed for all sludges since it offers a standard error of data fitting of less than 5%, in addition this model is not significantly different from the pseudo plastic one. Rheological properties cover a four order of magnitude range and follow a power type relation with TVS for the whole sector of sewage sludge and an exponential one for the OFMSW sector. Between 5–55°C, a positive temperature sensitivity is shown, while the activation energy is not significantly different from that of water. A high thixotropic nature is found in sewage and a low one in OFMSW sludge. A power relation with the TVS content is verified only for the sewage sludge sector.
Effect of mixing on the rheological characteristics of conditioned sludge: full-scale studies
Authors: Abu-Orf Mohammad M. , Dentel Steven K.
Published: May 2018

Conditioning of wastewater sludges with polyelectrolytes prior to dewatering is necessary to increase the sludges' dewaterability. During this conditioning process adequate mixing of the conditioner and the sludge must be attained. This research reports on results from full-scale experiments conducted to examine the effect of mixing parameters upon the conditioned sludge and liquid stream rheological characteristics.

Full-scale experiments were conducted at the 90 MGD Wilmington Pollution Control Facility. Varied mixing conditions were the rotational speed of the flocculation tank prior to dewatering and the filtrate recycling to the flocculation tank. The rheological changes in the conditioned sludge were detected using an on-line ZenoFloc™ system.

Although previous investigations have shown effects of such variations with regard to CST, use of a rheometer as indication of the rheological changes also showed that G variations led to different rheological levels. This allows some insight into conditioning mechanisms as well as optimization. Results also showed that mixing must be optimized and controlled for better dewatering performance.
The rheology of sewage sludge at different steps of treatment
Authors: Lotito V. , Spinosa L. , Mininni G. , Antonacci R.
Published: May 2018

Rheological parameters are very important in sewage sludge management, not only as designing parameters in transporting, storing, landfilling and spreading operations, but also as controlling ones in many treatments, such as stabilisation and dewatering. To study how different treatments affect sludge rheological behaviour, research has been undertaken at CNR-Istituto di Ricerca Sulle Acque (CNR-IRSA), and the preliminary results are discussed in this paper. Sludge samples taken from three municipal wastewater treatment plants at different steps of treatment have been tested by a rotational viscometer and data interpreted through both Bingham plastic and Ostwald pseudoplastic models. Coefficients of those models have been then correlated to solids concentration. Results confirmed that solids concentration is the main parameter affecting sludge rheology and evidenced that a single parameter is not sufficient to represent the rheological behaviour, thus indicating that other parameters should be introduced and characteristics considered for a better understanding of the phenomenon.
Changes of some sewage sludge parameters prepared with an ultrasonic field
Authors: Bien January , Wolny Lidia
Published: May 2018

Studies of sewage sludge conditioning by ultrasonic field concentrate on determination of the increase of water removal effect, which depends on kind of sludge and chemical compounds used in the dewatering process.

An attempt was made to find new methods of sludge preparation before dewatering. Tests presented here focused on digested and difficult dewatered sludge. The sludge was dewatered on a vacuum filter after conditioning with polyelectrolytes and the ultrasonic field. The microscopic analysis was an additional criterion to evaluate changes in the sludge structure after preparation. The polyelectrolyte dose of 3 mg/g d.m. sonicated within 15 sec. resulted in the 50% decrease of sludge volume. Results presented confirmed our previous experiences, concerning the relation between conglomerates of sludge and the effect of dewatering.