bluuebunny/crossref_metadata_2025 huggingface dataset:
Enhanced anaerobic degradation of mechanically disintegrated sludge
Authors: Baier Urs , Schmidheiny Peter
Published: May 2018

Mechanical disintegration - wet milling - was chosen to physically disrupt cellular material. By breaking up microbial or plant cell walls intracellular carbon sources as well as nutrients are made available for further anaerobic digestion. Ball milling consistently showed better disintegration results than high speed cutter milling. With respect to solubilisation of COD a high degree of cell disruption could be achieved in a variety of aerobic and anaerobic sewage sludges, where the fraction of soluble COD could be changed from 1–5% in original sludges to up to 47% after wet milling. In distillery slops and brewery residues milling failed to enhance soluble COD significantly.

Anaerobic digestion testing showed a good digestability of the solubilized intracellular material and consistently enhanced overall COD-degradation of the sludges by a factor of 1.2–1.5. Net biogas production was enhanced in the same order of magnitude. Stabilised sludges showed a higher beneficial effect of wet milling than raw excess sludge.
Enhancement of sludge anaerobic digestion by using of a special thickening centrifuge
Authors: Dohányos Michal , Zábranská Jana , Jenícek Pavel
Published: May 2018

The intensification method of anaerobic methane fermentation of sludges, based on the stimulation activity of cell lysate, was studied. The effect of lysate is caused by the still remaining activity of released enzymes and by the stimulating properties of other compounds that are present inside the cells. The use of cell lysate as a stimulating agent was examined in the laboratory experiments of anaerobic degradation of municipal raw sludge, excess activated sludge and a mixture of them. The cell lysate was prepared by a partial mechanical destruction of cells of the excess activated sludge by a special adapted thickening centrifuge.

The presence of aerobic 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 and biodegradability is influenced by the quality of input excess activated sludge and the parameters and efficiency of the thickening centrifuge. The improvement of methane yield from thickened activated sludge ranged from 8.1 to 86.4% dependent on the sludge quality. The improvement of methane yield from the mixture of thickened activated sludge and primary sludge ranged from 0 to 24%, and it was predominantly dependent on the fluctuating quality of primary sludge.

The advantages of the stimulation method with the cell lysate are the following: the improvement of the anaerobic biodegradability of organic materials treated, the acceleration of the degradation process, the increment of methane production, the lowering of digested sludge amount and the improvement of the energetic balance of the process.
Using metazoa to reduce sludge production
Authors: Rensink J. H. , Rulkens W. H.
Published: May 2018

Pilot plant experiments have been carried out to study the mineralization of sludge from biological wastewater treatment plants by worms such as Tubificidae. Trickling filters filled with lava slags were continuously fed with a certain quantity of excess activated sludge of a Dutch brewery wastewater treatment plant (Bavaria) by recirculation during 10 to 14 days. At the starting point of each experiment the trickling filters were inoculated with Tubificidae. Recirculation of sludge showed that use of Tubificidae resulted in a COD reduction of the sludge (mixed liquor) of 18–67–. Without worms this reduction was substantially lower. The sludge production in a pilot activated sludge system for treating settled domestic wastewater reduced from 0.40 to 0.15 g MLSS/g COD removed when Tubificidae were added to the system. The lower amounts of sludge were always accompanied by an increase of nitrate and phosphate concentration in the wastewater. There was no disturbance of the nitrification process. Application of Tubificidae or other worms may have interesting potential for practical application.
Aerobic composting and anaerobic digestion of pulp and paper mill sludges
Authors: Jokela Jari , Rintala Jukka , Oikari Aimo , Reinikainen Olli , Mutka Kari , Nyrönen Timo
Published: May 2018

The feasibility of aerobic vessel composting and anaerobic digestion for the treatment of pulp and paper mill sludges were studied. The composting studies made use of primary and secondary sludge from a de-inking and paper mill. In six parallely aerated 500 1 vessels with various carbon : nitrogen (C:N) -ratios, the most optimal performance was obtained with C:N -ratios of c. 22–35, while higher and lower ratios delayed the temperature increase. With the optimal ratios, the thermophilic stage was reached within 36 h, and the stage lasted for about seven days. In the scale-up study (18 m3 compost vessel), the thermophilic stage was reached within 24 h. An effective dehydratation of the mass was obtained as the total solids (TS) content of the compost increased from 31.3– to 63.8– within 21 days.

The anaerobic digestion of pulp and paper mill sludges was studied using two mesophilic 5 1 digesters, their feed sludges consisting of a mixture of municipal sewage sludge and primary and secondary sludge from a pulp and paper mill. With this feed mixture and with a loading rate of about 1.0 kg volatile solids (VS)/m3d a removal of about 27 to 40– VS and methane production of about 180 1/kgVSadded feed sludge were achieved during the 80 d study period.

The study showed that pulp and paper mill sludges are amenable to both aerobic composting and anaerobic digestion.
Volatile fatty acid production in aerobic thermophilic pre-treatment of primary sludge
Authors: McIntosh K. B. , Oleszkiewicz J. A.
Published: May 2018

The efficiency of volatile fatty acid (VFA) production in a thermophilic aerobic digester (TAD) process using primary sludge was studied under two oxygenation states and detentions times ranging from 12 to 24 hours. The highest VFA concentration increase occurred in the 18 hour anaerobic aerated digester (O2 flow rate: 0.025 m3/m3·h; ORP: less than -300 mV) from 0.047 mg HAc/mg VSS in the feed to 0.106 mg HAc/mg VSS in the effluent. The anoxic condition (O2 flow rate: 0.14 m3/m3·h; ORP: between 0 to -225 mV) resulted in VFA utilisation and a final concentration of only 0.001 mg HAc/mg VSS. Under the anaerobic aerated condition, acetic acid constituted the largest fraction of short chain volatile fatty acids at an average of 60.4% and propionic trailed at 19.3%. The fraction of butyric and valeric acids were 12.2% and 8.1% respectively. It was found that with a decreasing oxygen supply and a decreasing detention time (HRT), the soluble organic carbon to ammonia ratio (SOC:NH3) increased.
Reduction of fecal streptococcus and salmonella by selected treatment methods for sludge and organic waste
Authors: Jepsen Svend-Erik , Krause Michael , Grüttner Henrik
Published: May 2018

The increasing utilization of waste water sludge and source-separated organic household waste in agriculture has brought the quality aspects into focus, among others the hygienic aspects. In this study, the reducting effect on Fecal Streptococcus (FS) and Salmonella of different methods for stabilization and methods for further treatment of sludge and organic waste has been investigated. The most common methods for stabilization, i.e. aerobic and anaerobic stabilization, only reduce the indicator organisms by approximately 1 logarithmic decade. Methods for further treatment of sludge and organic waste have shown reductions of microorganisms allowing for unrestricted utilization in agriculture, meeting the product control: FS below 100/g and no Salmonella detected.

The effect of storage of sludge at summer and winter temperature respectively has been investigated. At temperatures (around 20°C) significant reductions of Salmonella were found, while the die out at low temperatures (below 10°C) was limited. FS was not reduced systematically during storage, and therefore, FS is not usable as indicator organism for the hygienic properties of sludge during storage.
Resource recovery of sludge as a building and construction material – a future trend in sludge management
Authors: Tay Joo-Hwa , Show Kuan-Yeow
Published: May 2018

Rapid urbanization in many areas of the world has resulted in an drastic increase of wastewater sludge. In highly urbanized cities, sludge disposal by landfilling may no longer be appropriate owing to land scarcity and increasingly stringent environmental control regulations. Therefore future trends in sludge management are towards minimization and reutilization as useful resources. Incineration is one feasible means of converting bulky sludge to practically inert, odorless and sterile ash. The disposal of this significantly reduced volume of sludge ash can be subsequently handled easily with much smaller scale. The disposal problems will be drastically reduced if sludge or sludge ash can be put to large-scale economic applications. This paper reviews current studies by various researchers in reutilising sludge as non-conventional construction materials. Properties of the innovative materials derived from sludge, the processing technology, and the suitability of the materials for construction purposes will be discussed. A summary of the research work carried out by the authors in the past ten years, specifically in the area of sludge reutilization as building bricks, lightweight aggregates, and cementitious material will also be presented.
Simulation of the operational conditions of the full-scale municipal wastewater treatment plant to improve the performance of nutrient removal
Authors: Funamizu Naoyuki , Yamamoto Shoichiro , Kitagawa Yoshio , Takakuwa Tetsuo
Published: May 2018

Simulation analysis based on a mathematical model is one of the powerful tools for determining the operational conditions for a full scale biological nutrient removal plant. The model that included the Activated Sludge Model No.2 was developed for simulating the performance of the plant in Sapporo City. The investigated plant has the biological reaction basin which consists of the four zones, anaerobic-aerobic-anoxic-aerobic phases with the step feed of the primary effluent to the anaerobic and anoxic zones. We performed three experiments to calibrate and verify our model: (i) Characterization of organic matters in the influent of the reaction basin with the OUR measurement method; (ii) Measurement of COD and nutrient concentration at the plant; (iii) Lab-scale batch experiments with the anaerobic-aerobic-anoxic-aerobic phases. The calibrating process of the model showed that no modification of parameter values was required to evaluate the performance of the plant and population of the activated sludge. Simulated results showed that the choice of the sewage step feed ratio did not affect the nitrogen removal and that the denitrification rate in the anoxic zone was controlled by the hydrolysis rate of the slowly biodegradable organic matters. The results of the lab-scale experiment and simulation results showed that the addition of the readily biodegradable organic matters like fermentation products of the primary settler sludge was effective to improve the performance of nitrogen removal.
Effects of SRT and DO on nutrient removal in a combined AS-biofilm process
Authors: Chuang S. H. , Ouyang C. F. , Yuang H. C. , You S. J.
Published: May 2018

This study examines the effects of sludge retention time (SRT) and dissolved oxygen (DO) on COD, nitrogen and phosphorus removal in a combined activated sludge - biofilm process. Various SRT (5, 10, 12 and 15 days) and dissolved oxygen (0.1, 0.5, 1.0 and 2.0 mg/l in aerobic stage) conditions are performed during the hybrid process. Experimental results indicate that SRT significantly affects the behavior of nitrogen and phosphorus removal, although the variation of COD removal is only slight in different SRT experiments. The SRT should be controlled for longer than 10 days to achieve efficient nitrogen removal. However, a SRT less than 12 days is deemed necessary to complete the phosphorus removal. The process displays similar characteristics when dissolved oxygen is operated between 1.0 to 2.0 mg/l in the aerobic stage. Moreover, analyzing polyhydroxyalkanoates (PHAs) reveals that phosphorus release and uptake are closely related to PHAs accumulation and utilization, respectively, during anaerobic, anoxic and aerobic stages of the process. The ratio of phosphorus uptake and PHAs utilized, rP/PHAs, denotes a dissimilar trend during anoxic and aerobic stages. The sludge has a high efficiency in utilizing PHAs for phosphorus uptake in anoxic stage when it is under lower COD-SS loading conditions. The value of rP/PHAs ranges from approximately 0.1 to 1.0 mg P/mg PHAs. In addition, experimental results also demonstrate that anoxic phosphorus uptake can improve phosphorus removal in biological nutrient removal processes.
Emission of nitrous oxide from high-rate nitrification and denitrification by mixed liquor circulating process and sequencing batch reactor process
Authors: Okayasu Yuji , Abe Isaya , Matsuo Yoshitaka
Published: May 2018

Laboratory scale models simulating a mixed liquor circulating (MLC) process and a sequencing batch reactor (SBR) process were operated with a high ammonium volumetric loading to study the possible nitrous oxide (N2O) emission from them. The N2O emission from the MLC process was found to depend on the DO level in the aerobic reactor. When the DO level was high, the emission was negligibly small. The SBR reactor emitted N2O in a quantity as high as 40 percent of the removed nitrogen. Most of the emission occurred during the low DO period in the aeration stage.
Biological dephosphatation by activated sludge under denitrifying conditions: pH influence and occurrence of denitrifying dephosphatation in a full-scale waste water treatment plant
Authors: Kuba T. , van Loosdrecht M. C. M. , Heijnen J. J.
Published: May 2018

The effect of pH on phosphorus release under anaerobic conditions was examined for denitrifying phosphorus removing bacteria (DPB) cultivated in an anaerobic-anoxic sequencing batch reactor. Also batch tests were conducted with activated sludge from a full-scale waste water treatment plant (WWTP) in order to investigate occurrence and contribution of DPB in phosphorus removal processes. In the experiments for the pH effect, enriched DPB sludge was maintained under anaerobic conditions with acetic acid (HAc) present at 5 different pH conditions (6.0∼8.0), and released phosphorus and consumed HAc concentrations were measured. When the biomass concentration was around 2.7 g-VSS/l, the observed P/C (released-P/consumed-HAc) ratios were 0.7, 1.1 and 1.2 g-P/g-C at pH=6, 7 and 8. At 4.2 g-VSS/l, the observed P/C ratios were 0.9, 1.3 and 1.2 g-P/g-C, respectively. The difference between the two experiments resulted from the endogenous phosphorus release. The same pH effect as observed for conventional anaerobic-aerobic SBR sludge, was obtained for the DPB sludge in the range of pH=6.0∼7.5. However due to precipitates formation at pH=8.0, the apparent P/C ratio was approximately 20% less than the ratio calculated from the biological released phosphorus concentration by DPB. From the results of the batch tests with activated sludge and observations on the full-scale WWTP, it was also shown that clearly denitrifying dephosphatation occurs and approximately 50% of the phosphorus removal occurs via denitrifying activities in the WWTP.
Development of novel anaerobic/aerobic filter process for nitrogen removal using immobilized nitrifier pellets
Authors: Kim Youngno , Mikawa Kazuhiro , Saito Toshiaki , Tanaka Kazuhiro , Emori Hiroyoshi
Published: May 2018

In Japan, priority of sewage works implementation has gradually been given to smaller communities. Sewage treatment processes for small communities must meet several requirements such as low construction and O-M cost, easy O-M, stable performance, and in some locations nitrogen and/or phosphorus removal as well as BOD and SS removal. With a view to achieving these requirements, the authors have been developing a novel anaerobic/aerobic filter process for simultaneous removal of BOD, SS and nitrogen. In this process, an upflow anaerobic filter is followed by a nitrification tank using entrapped immobilized nitrifier pellets and an aerobic filter for the polishing process. In order to demonstrate this novel process in the field, a pilot plant with a capacity of 1.75 m3/d was installed in an existing sewage treatment plant near Tokyo in January, 1996. The target effluent qualities are BOD and T-N less than 10 mg/l respectively and SS less than 5 mg/l. The pilot plant study has shown that the overall treatment performance of 96∼97% in SS and BOD removal and 74∼75% in T-N removal has been stably obtained under the conditions of 5.5h in total retention time, recycling ratio of 3, and 25 to 250% in load variation.
Treatment of domestic wastewater mixed with crushed garbage and garbage washing water by advanced gappei-shori johkaso
Authors: Sankai Toshihiro , Ding Guoji , Emori Noritoshi , Kitamura Satoshi , Katada Kensho , Koshio Akihiko , Maruyama Tatsushi , Kudo Keiko , Inamori Yuhei
Published: May 2018

By using an advanced anaerobic filter-contact aeration Gappei-shori Johkaso (AFAJ), a small-scale wastewater unit used in Japan, experiments of the treatment of the wastewater mixed with domestic wastewater and disposer wastewater which came from washing water of crushed garbage by disposer were made. After the introduction of disposer wastewater into domestic wastewater, BOD, TN and SS loads increased to 1.7 times, 1.1 times and 1.7 times, respectively. Results showed that in the 5-person-use type AFAJ, no remarkable decrease appeared to the BOD and SS removal efficiencies after introduction of disposer wastewater into domestic wastewater, however, TN removal efficiency decreased significantly. As a result, effluent BOD and TN concentrations were much higher than 20 mg·l−1. On the other hand, the 7-person-use type AFAJ, whose volume was 35 % bigger than that of the 5-person-use type AFAJ, could treat the above wastewater to be less than 20, 10 and 20 mg·l−1, respectively. In addition, it was shown that not many changes took place in the kinds and occurrence frequencies of protozoa and metazoa after the addition of the disposer wastewater, which suggested that the addition of disposer wastewater had increased the BOD and SS loads while it did not lead to much change in the component of the domestic wastewater.
Application of air backflushing technique in membrane bioreactor
Authors: Visvanathan C. , Yang Byung-Soo , Muttamara S. , Maythanukhraw R.
Published: May 2018

The optimum air backflushing and filtration cycle was investigated for a 0.1 μm hollow fiber membrane module immersed in an activated sludge aeration tank. It was found that 15 minutes filtration and 15 minutes air backflushing gave the best result both in terms of flux stability and net cumulative permeate volume. Although this cyclic operation could not completely remove the clogging, this process improved the flux by up to 371% compared to the continuous operation.

During the long term runs, three different hydraulic retention times (HRT) of 12, 6 and 3 hours, corresponding to 0.16, 0.32 and 0.64 m3/m2.d of permeate flux respectively, were investigated. Stable operation was obtained at the HRT of 12 hours. Decrease in HRT led to rapid formation of a compact cake layer on the membrane surface thus increasing the transmembrane pressure. It was also noted that filtration pressure increases with increase in bioreactor MLSS concentration. With operation time, the MLVSS/MLSS value decreased without significant effect on the process performance, indicating that inorganic mass constantly accumulated in the bioreactor. All the experimental runs produced more than 90% removal of COD, and TKN. In terms of physical, chemical, biological and bacteriological parameters, the membrane bioreactor effluent was superior to the conventional activated sludge process.
Effect of high concentration of organic and inorganic matters in landfill leachate on the treatment of heavy metals in very low concentration level
Authors: Urase T. , Salequzzaman M. , Kobayashi S. , Matsuo T. , Yamamoto K. , Suzuki N.
Published: May 2018

Various heavy metals in the landfill leachates were measured up to very low concentration levels of micrograms per litre. Though no violation to Japanese effluent standards was found in respect of individual metal, leachate or treated leachate it still contains higher concentrations of total heavy metals than surrounding water environment. The effluent concentration after treatment was of the same order as raw leachate. Maximum metal solubilities in leachate were calculated taking the presence of inorganic metal complexes into account. Solubilities of metals were high enough and they were not the limiting factor determining concentrations after coagulation. The coagulation with higher pH was not successful in reducing concentration of leachate - origin - metals contrary to the case of pure chemical metals. The heavy metals especially nickel and copper in the leachate were associated with organic matter and consequently they remained in solution unless organic matter was removed. Application of nanofiltration to leachate treatment was studied. It was possible to separate metals from less toxic salts by low retention nanofiltration membranes.
Biotreatability test of bleach wastewaters from pulp and paper mills
Authors: Wang X. , Mize T. H. , Saunders F. M. , Baker S. A.
Published: May 2018

Research is focused on an integrated way to simultaneously optimize the bleaching operations and subsequent wastewater treatment for pulp and paper mills. Bleach wastewaters from ClO2-bleached pulping studies at Institute of Paper Science and Technology (IPST) were used as the feed for batch reactors to test and rank the treatability and kinetics. The key aspect of the system is the use of sequential anaerobic/aerobic phases to enhance reductive dehalogenation of chloro-organic materials. Two continuous reactor systems, one operated in an anaerobic-aerobic mode and a second in an aerobic-aerobic mode, received bleaching wastewater obtained from a full-scale plant. Acclimated cultures from both continuous reactors were used to quantify the AOX (Adsorbable Organic Halide) and COD removal from various bleaching wastewaters. In general, the sequential anaerobic/aerobic treatment of bleach wastewater can improve both biotreatability and degradation rates.
Biological nitrification of kraft wastewater
Authors: Bryant Curtis W. , Barkley W. A. , Garrett Michael R. , Gardner David F.
Published: May 2018

A program of batch, continuous-flow, and field pilot tests have been conducted to measure the extent and stability of nitrification in kraft wastewater. Laboratory batch tests measured the extent and rate of ammonia removal from kraft wastewater. Controlled variables included aerated stabilization basin (ASB) location, temperature, pH, ammonia concentration, black liquor content, bicarbonate content, and presence of acclimated nitrifying bacteria. Findings were that (a) moderate wastewater temperature (22-35°C), pH near 7.3, and black liquor spill control prevented slowing of nitrification, and (b) provision of acclimated nitrifying bacteria (by appropriate recirculation methods) dramatically reduced the residence time needed for nitrification in kraft ASBs. Laboratory-scale, fixed-film, continuous-flow tests were used to investigate dynamic responses to changes in wastewater composition and flow. Results demonstrated that the nitrifying films were not ‘damaged’ by 4- or 24-hour step increases in influent ammonia, but the films could not respond quickly enough to substantially dampen out the effect on effluent quality.

A pilot 4-stage rotating biological contactor (RBC) was installed at an ASB to test the nitrification of kraft wastewater under actual process variations. The results during the 11-month run were: (a) the RBC demonstrated capability to consistently and substantially reduce NH4-N concentration below 1 mg/L, (b) about one month was needed to establish effective treatment, and (c) effective treatment was sustained at a maximum hydraulic loading rate of 0.11 m3/day per m2.
Pretreatment of azo dyes using ozone
Authors: Liakou S. , Kornaros M. , Lyberatos G.
Published: May 2018

Wastewaters produced in textile industrial processes contain organic dyes which are not easily amenable to biological treatment. Pretreatment with ozone is a promising method for oxidation of those dyes to more degradable compounds. The aim of this work is to assess the oxidation kinetics of a specific azo dye used in the textile industry, Orange II. Batch experiments were conducted in order to elucidate the oxidation route of the dye. Oxalate, formate and benzenesulfonate are found to be the oxidation intermediate compounds. A mathematical model which describes the dye elimination, the COD and BOD5 variation, the amount of ozone reacted and the time evolution of the intermediate compounds has been developed.
Enhanced biodegradability by oxidative and radiative wastewater treatment
Authors: Möbius Christian H. , Cordes-Tolle Maria
Published: May 2018

Processes for oxidative destruction of non-biodegradable substances in wastewater of the pulp and paper industry are using oxidants, partly in combination with catalysts or high energy radiation including UV-radiation. We summarize these processes as oxidative and radiative treatment. Instead of aiming at a total oxidation of the organic matter a partial oxidation of the persistent substances can be achieved with far less costs in biological treated wastewater. This leads to a significant improvement of the biodegradability. A subsequent biological treatment will eliminate therefore a high proportion of the remaining organic matter, which before was persistent. Special processes are needed for the additional biological treatment due to the low BOD concentration. Low loaded biofilm reactors like submerged granular biofilters have been established as the most preferred technique for this treatment. A process of this type that has been extensively studied by us is ozonation of biological treated wastewater followed by biological treatment with biofilters.
Laboratory studies on the temperature-phased ASBR system
Authors: Welper Lana L. , Sung Shihwu , Dague Richard R.
Published: May 2018

Treatment of high-strength industrial wastewater with the temperature-phased anaerobic sequencing batch reactor (ASBR) system has shown positive results in laboratory scale studies. The system achieved COD removals as high as 95% and 90% for soluble and total COD, respectively, up to COD loadings of 22 g COD/L/day. Non-fat dry milk was used as a synthetic substrate.

The system consisted of two reactors operated in series at different temperatures. Phase I of the system was operated at 55°C and the Phase II was operated at 35°C. The total hydraulic retention time in the system was 18 hours (6 hours in the Phase I and 12 hours in the Phase II). The temperature-phased system incorporates advantages of both thermophilic treatment (high reaction rates) and mesophilic treatment (higher quality effluent) while minimizing the disadvantages such as odors commonly associated with thermophilic treatment and lower treatment rates of mesophilic treatment.

This study was conducted using ASBRs. The ASBR was developed at Iowa State University by R.R. Dague. This process allows biomass to increase in the reactors and provides an environment for granulation to occur. Although the ASBR was used for these studies, the temperature-phased process is applicable to other anaerobic treatment processes as well.
Continuous removal of heavy metals from FGD wastewater in a fluidised bed without sludge generation
Authors: Nielsen P. B. , Christensen T. C. , Vendrup M.
Published: May 2018

A patent pending fluid-bed process has been developed by Krüger for removal of dissolved heavy metals by adsorption/coprecipitation. The waste product is a very compact granulate with a very low water content of 10-20%. Sludge is not produced. The fluid-bed technique was tested at a coal-fired power station with wastewater from the flue gas desulphurisation (FGD) unit for removal of heavy metals from the wastewater. By dosing only potassium permanganate to the wastewater, the content of dissolved nickel, cadmium and zinc was reduced by respectively 99%, 92% and 97% at optimum treatment in one fluid-bed reactor. The weight of waste product produced will constitute less than 25% of the waste product produced by the present traditional chemical precipitation. Chemical costs are approximately 0.6 US$/m3 which are similar for the fluid-bed and present wastewater treatment processes.
Biodegradation of selected azo dyes under methanogenic conditions
Authors: Razo-Flores Elías , Luijten Maurice , Donlon Brian , Lettinga Gatze , Field Jim
Published: May 2018

Biological treatment of wastewaters discharged by the textile industry could potentially be problematic due to the high toxicity and recalcitrance of the commonly-used azo dye compounds. In the present report, the fate of two azo dyes under methanogenic conditions was studied. Mordant Orange 1 (MO1) and Azodisalicylate (ADS) were completely reduced and decolorised in continuous UASB reactors in the presence of cosubstrates. In the MO1 reactor, both 5-aminosalicylic acid (5-ASA) and 1,4-phenylenediamine were identified as products of azo cleavage. After long adaptation periods, 5-ASA was detected at trace levels, indicating further mineralization. ADS, a pharmaceutical azo dye constructed from two 5-ASA units, was completely mineralized even in the absence of cosubstrate, indicating that the metabolism of 5-ASA could provide the reducing equivalents needed for the azo reduction. Batch experiments confirmed the ADS mineralization. These results demonstrate that some azo dyes could serve as a carbon, energy, and nitrogen source for anaerobic bacteria.
Characterization of an anaerobic soil enrichment capable of dechlorinating high concentrations of tetrachloroethylene
Authors: Lee Tae Ho , Yoshimi Masaharu , Ike Michihiko , Fujita Masanori
Published: May 2018

An anaerobic soil enrichment culture could dechlorinate high concentrations of tetrachloroethylene (PCE; 150 mg/liter nominal concentration; approximately 58 mg/liter in aqueous concentration) nearly stoichiometrically to cis-1,2-dichloroethylene (cis-DCE) via trichloroethylene (TCE) at high rates; a maximum dechlorination rate was 0.4 μmol of PCE transformed/mg volatile suspended solids per hr, using citrate as an electron and carbon source and yeast extract as a nutritional requirement. This dechlorinating activity was comparable with those of the previously-reported, efficient bacterial cultures. Some substrates such as pyruvate, succinate, formate, acetate, and acetate with H2 could replace citrate but propionate could not, and yeast extract could be replaced by a vitamin mixture. However the PCE dechlorination rate decreased more than threefold by the addition of the vitamin mixture, suggesting that the vitamin mixture could not be a complete supplement for the nutritional requirement. Optimal pH and temperature of the enrichment for PCE dechlorination were 7 and 30 °C, respectively. Dechlorination of PCE was completely inhibited by the addition of NO3− and NO2− as potential alternative electron acceptors. S2O3−2 and SO3−2 delayed PCE dechlorination but SO4−2 had no significant effect on PCE reduction. 2-bromoethanesulfonic acid (BES, an inhibitor of methanogenesis) also showed no influence on PCE dechlorination, suggesting methanogens were not concerned with PCE removal in this enrichment. Further, microbial investigations on the enrichment showed that it contains four types of bacteria; cocci, large rods, curved rods, and small rods. The small rods seemed to nutritionally support the PCE dechlorinating bacteria, presumably the curved rods.
Modelling anaerobic codigestion of manure with olive oil mill effluent
Authors: Angelidaki Irini , Ellegaard Lars , Ahring Birgitte K.
Published: May 2018

A mathematical model describing the combined anaerobic degradation of complex organic material, such as manure, and a lipid containing additive, such as olive oil mill effluents, has been developed based on a model previously described (Angelidaki et al. 1993). The model has been used to simulate anaerobic codigestion of cattle manure together with olive oil mill effluent (OME) and the simulations were compared with experimental data. Simulation data indicated that lack of ammonia, needed as nitrogen source for synthesis of bacterial biomass and as an important pH buffer, could be responsible for the problems encountered when anaerobic degradation of OME alone is attempted. It was shown that the amount of nitrogen needed to obtain a stable degradation of OME can be provided by manure during codigestion of OME and manure.
Hydrogen gas production from glucose and its microbial kinetics in anaerobic systems
Authors: Majizat Akashah , Mitsunori Yoshida , Mitsunori Watanabe , Michimasa Nakamura , Jun'ichiro Matsumoto
Published: May 2018

The acidogenic phase of a continuous stirred tank reactor (CSTR) inoculated with well acclimated sludge will produce a substantial amount of hydrogen gas and steady state microbial biomass. Hydrogen production of more than 65% was observed at high dilution rate and 71% at low dilution rate. Gas production rate of more than 10 1/day was also observed from the chemostat reactors. The true yield (Yt) value was 0.625 g.VSS/g.COD-utilized and the kd value was 0.41 hr-1. Sample sludge (cell) from chemostat reactors was then collected at steady state and small amount was inoculated into small vials. Many sets of vials were prepared and all were filled up by different concentrations of glucose and growth medium with the same proportion. The vials were treated as batch culture of the mixed microorganisms, incubated at 30°C and put on a rotating shaker with 130 osc.min.-1. The VSS values analyzed on the vials sample at predetermined time intervals will provide the data for the inhibitory constants determinations. From the available kinetics parameters and inhibitory model equation, graph fittings computations were done. The inhibitory model fits to some degree on the experimental data. These findings confirmed the inhibitory effects of glucose concentrations and the ability to recover hydrogen gas from organic substances at certain predetermined concentrations.
Convective flow in methanogenic granules
Authors: Van den Heuvel J. C. , Beuling E. E. , Van Dusschoten D. , Roosenschoon O. L. , Verschuren P. G.
Published: May 2018

Gas bubbles entrapped in biocatalyst particles subjected to hydrostatic pressure oscillations, e.g. during recirculation in loop reactors, will induce intraparticle liquid flows, and thereby enhance mass transfer in excess of diffusion. This ‘breathing particle’ mechanism was already demonstrated in methanogenic granules from an IC reactor, and led to an average macroscopic activity increase of 13%. The existence of the alternating convective liquid flow responsible for this higher activity has now been established independently with pulsed field gradient NMR, as the intraparticle water mobility during pressure oscillations was found 16.5% larger. Micro-electrode measurements of the internal pH of a granule revealed the occurrence of a fast liquid flow through a channel between a central cavity and the periphery during pressure cycling, and the subsequent diffusive relaxation under atmospheric conditions.
An effective start-up of thermophilic UASB reactor by seeding mesophilically-grown granular sludge
Authors: Syutsubo Kazuaki , Harada Hideki , Ohashi Akiyoshi , Suzuki Hiroshi
Published: May 2018

After seeded with mesophilically-grown (35°C) granular sludge, a laboratory-scale UASB reactor was thermophilically (55°C) operated over 8 months by feeding with an alcohol distillery wastewater. Use of mesophilically-grown granules as a seed material proved to be more advantageous for rapid and stable start-up of thermophilic UASB process, compared with the use of suspended-growth sludge taken from a thermophilic anaerobic digester. The reactor accommodated successfully a COD loading 30 kgCOD·m−3·d−1, with a COD removal efficiency of 85%. However, during a period of 30 kgCOD·m−3·d−1, propionate accumulated in the effluent up to 300-600 mgCOD·l−1. Thermophilic cultivation caused a drastic increase of methanogenic activities (55°C) of the retained sludge: 4.4 times for acetate, 4.6 times for propionate, and 3.5 times for hydrogen as large as those of the seed sludge. A considerably low value of propionate-fed methanogenic activity, i.e. only 1/5 of acetate-fed activity and only 1/23 of hydrogen-fed activity, suggested that the propionate degradation is subject to be a rate-limiting step in thermophilic anaerobic processes.
Treatment of raw sewage in a temperate climate using a UASB reactor and the hanging sponge cubes process
Authors: Agrawal Lalit K. , Ohashi Yasuhiro , Mochida Etsuo , Okui Hiroyuki , Ueki Yasuko , Harada Hideki , Ohashi Akiyoshi
Published: May 2018

The treatability of raw sewage in a temperate climate (wintertime around 10–20°C) using an upflow anaerobic sludge blanket (UASB) reactor and the hanging sponge cubes process was evaluated. After being seeded with digested sewage sludge, a 47.1 L UASB reactor was continuously operated for more than 2 years by feeding raw sewage, which had average COD around 300 mg/L (41% soluble). During summertime at an HRT of 7 h, effluent COD approximately 70 mg/L total, 50 mg/L soluble and BOD5 20 mg/L total, 12 mg/L soluble was obtained. During wintertime also, treatment efficiency and process stability was good.

With the hanging sponge cubes process using the effluent of the UASB reactor treating raw sewage, the following results were obtained. The ammonia oxidation rates of 1.9 and 3.5 g NH4-N·m−2·d−1 in a downflow hanging sponge cubes biofilter, under natural air intake only were obtained during wintertime and summertime, respectively. With post-denitrification and an external carbon source, 84% in average N (NO3+NO2) was removed with an HRT of less than 1 hour and in the temperature range of 13 to 30°C using an upflow submerged hanging sponge bed bioreactor, under anaerobic conditions. The overall system using a UASB reactor and the hanging sponge cubes process could be quite an attractive treatment alternative.
Two-phase anaerobic treatment of cane-molasses alcohol stillage
Authors: Yeoh B. G.
Published: May 2018

Anaerobic treatment of cane-molasses alcohol stillage was studied in a thermophilic two-phase system comprising two bioreactors for the acidogenic and methanogenic phases respectively in comparison with the single-phase process. The experiments were conducted with HRT ranging from 36.0 to 9.0 days for single-phase and from 32.7 to 5.6 days for two-phase, corresponding to organic loading rates of 3.452 to 14.487 and 4.646 to 20.022 kgCODm−3day−1 respectively. The treatment efficiency was essentially maintained at BOD5 and COD removal of over 85% and 65% respectively in the two-phase process even with higher substrate loading. The acidogenic phase provided satisfactory conversion of initial COD to VFA averaging 15.6% in the degree of acidification. The methanogenic culture pH of both systems was maintained in a range of 7.4 to 7.8 through self regulation. The methane content of the biogas generated from the two-phase process was significantly higher by about 17% than that from the single-phase process, both decreasing with increasing substrate loading and shorter HRT. The mean overall methane yield was found to be 0.168 m3CH4(STP)kg−1 CODadded or 0.292 m3CH4(STP)kg−1 VSadded from two-phase methanogenesis, compared to 0.055 m3CH4(STP)kg−1CODadded or 0.082 m3CH4(STP)kg−1VSadded from single-phase fermentation. However, methane yield in the two-phase process was enhanced only at COD loading rates higher than 2.9 kgm−3day−1 or VS loading rates higher than 1.8 kgm−3day−1. The ultimate methane yield was evaluated graphically to be 0.216 m3CH4(STP)kg−1CODadded, or 0.401 m3CH4(STP)kg−1 VSadded. This indicated a methane yield efficiency of 73-78% for the two-phase anaerobic digestion of cane-molasses alcohol stillage, which was composed of 24.2% and 28.2% of non-biodegradable COD and VS respectively. Kinetic evaluation of the experimental data provided θm (minumum SRT) and K (kinetic constant) values as 6.6 days and 0.166 respectively based on COD, or 7.0 days and 0.160 respectively based on VS. Application of the two-phase anaerobic process on full scale at an industrial treatment plant for alcohol stillage showed mean treatment efficiency in terms of BOD5 and COD reduction of 84.3% and 63.2% respectively at an average loading rate of 5.1 kgCODm−3day−1, which was in good agreement with the bench-scale studies, considering the great variation in the raw wastewater characteristics typical of an industrial operation.
Causes and effects of foaming in anaerobic sludge digesters
Authors: Pagilla Krishna R. , Craney Kent C. , Kido Wendell H.
Published: May 2018

Full scale anaerobic digesters treating mixed sludge containing primary sludge and thickened waste activated sludge were investigated for causes and effects of foaming. Sludge samples were collected from different depths of two full scale digesters, one gas-mixed, and the other mechanically-mixed, to determine the extent of foaming and its effects on anaerobic digestion; both digesters were fed the same feed sludge (3.4% TS) and at the same feed rate (about 2.2 kg TS/m3.day). The average depth of the surface foam layer in the gas-mixed and mechanically-mixed digester were 2.4 and 1.3 m respectively. Higher total solids concentrations were found at the surface (about 5% TS) than those found at the bottom (about 2% TS) in both gas-mixed and mechanically-mixed digesters, indicating an inverse total solids profile. Presence of excessive levels of Nocardia filaments (>106 number/g VSS) in the activated sludge caused thicker foam layer at the surface, and this effect was more pronounced in the gas-mixed digester than in the mechanically-mixed digester. Gas-mixed digester (0.74 m3/kg VS destroyed) produced less sludge gas than the mechanically-mixed digester (0.93 m3/kg VS destroyed), however, gas-mixed digester (62% VS reduction) destroyed more volatile solids than the mechanically-mixed digester (54% VS reduction). These results indicate that gas-mixed digesters are more prone to foaming than mechanically-mixed digesters, and that the foaming can increase when excessive levels of Nocardia filaments are present in the feed sludge causing decreased digester performance.
Ecological analysis of the bacterial system in a full-scale egg-shaped digester treating sewage sludge
Authors: Li Y. Y. , Mizuno O. , Miyahara T. , Noike T. , Katsumata K.
Published: May 2018

A full-scale investigation was conducted to evaluate the treatment performance and the bacterial system in an egg-shaped digester treating sewage sludge. The experiment was continued over one year to measure the methanogenic activities using various substrates and the population levels of various trophic groups of methanogenic bacteria, as well as the degradation of each component of organic matters. A total of 10 full-scale egg-shaped sludge digesters fed with concentrated sludge were investigated in this study. At a retention time of 30 days and mesophilic condition of 36 °C, the average reduction efficiencies of carbohydrates, proteins and lipids, which are the three main components in raw sludge, were 74.2%, 55.2% and 42.2%, respectively. As a result, the removal efficiencies of volatile solids (VS) and total CODcr reached 54.2% and 60%, respectively, and 1 m3 influent concentrated sludge produced 23.3 m3 digestion gas in which methane content was about 60%. The comparison between the specific methanogenic activity and the actual specific methane production rate in the digester suggestes that the retention time of the digester could be reduced from 30 days to 15 days without affecting their performance. In addition, both the hydrogen and acetate-consuming methanogenic bacteria were enumerated on the order of 107 MPN/ml.
Hydrolysis constant and VFA inhibition in acidogenic phase of MSW anaerobic degradation
Authors: Borzacconi Liliana , López Iván , Anido Carlos
Published: May 2018

The most significant parameters of a model that simulates the hydraulic and biological behaviour of a sanitary landfill were determined. These parameters were particulate matter, hydrolysis constant, initial waste polluting potential, and waste porosity. Based on experimental data collected from two reactors, the acidogenic stage was characterized. There was an inhibition due to the accumulation of VFA in the reactor fed with a higher than usual content of easily biodegradable matter. In such reactors the methanogenic stage was never reached. The COD and VFA curves of the reactor where the methanogenic stage was attained, showed a maximum around the 200th day. After 500 days, a noticeable methane production started. Based on first order kinetics, the value of the particulate matter hydrolysis constant was determined to be 0.8×10−3d−1.
Consequences for established design practice from geographical variation of historical rainfall data
Authors: Mikkelsen P. S. , Arnbjerg-Nielsen K. , Harremoës P.
Published: May 2018

The Danish measuring network for high-resolution rainfall data was initiated in 1979 and consists of approximately 50 tipping bucket rain gauges separated by one to 300 km, covering an area of 43,000 square kilometres. T-year design events and the associated sampling error variances were estimated at each site using the bootstrap method and the partial duration series method and a methodology was developed for quantifying the inter-site correlation structure due to spatial coverage of rain storms. The data reveals a dramatic geographical (regional) variation that may be divided into true regional variation and variation due to (correlated) sampling errors. Further analyses indicate that the observed variation can be explained only partially by correlation with regional climatological variables and that a significant residual variation remains, especially for large return periods. The new perceptions question the value of local rain data for design and call for an increased use of statistical concepts in engineering design practice.
Stochastic simulation of urbanhydrological processes
Authors: Scholz Klaus
Published: May 2018

Calculations in urban hydrology have almost exclusively been of deterministic character and give therefore unequivocal results. Uncertainties, which are always present, can not been eliminated by more complex models. To take uncertainties into account stochastic algorithms are integrated into hydrological components. A stochastic-hydrological method has developed which can be used to various problems. In contrast to the usual purely deterministic models the model makes it possible to get concrete information of liability of the calibration and prognosis regarding confidence limits The model is applied for the calibration and prognosis of pollutant load hydrographs. The result is, that stochastic and physical based parameters should be taken into account.