bluuebunny/crossref_metadata_2025 huggingface dataset:
Multistage wastewater treatment using separated storage driven denitrification and nitrification biofilms
Authors: Hughes L. J. , Lancaster J. , Cord-Ruwisch R.
Published: July 2007

The feasibility of combining a previously reported storage driven denitrification biofilm, where 80% of influent acetate can be converted to poly-beta-hydroxybutyrate (PHB), with a suitable nitrification reactor, either submerged or trickling filter design, to achieve complete biological nitrogen removal was tested. The reactor system showed the potential of complete biological nitrogen removal of waste streams with a C/N ratio as low as 3.93 kg COD/kg N-NH3 at an overall nitrogen removal rate of 1.1 mmole NH3/L/h. While the efficiency and the rates of nitrogen removal were higher than what is observed in traditional or simultaneous nitrification and denitrification (SND) systems, there were two problems that require further development: (a) the incomplete draining of the reactor caused ammonia retention and release in the effluent, limiting the overall N-removal and (b) pH drifts in the nitrification step slowed down the rate of nitrification if not corrected by appropriate pH adjustment or buffering.
Real-time PCR quantification of nitrite reductase (nirS) genes in a nitrogen removing Fluidized Bed Reactor
Authors: Araki N. , Tsukamoto Y. , Nagano A. , Yamaguchi T. , Harada H.
Published: July 2007

Molecular approaches were applied to identify and enumerate denitrifying bacteria subsisting in a fluidized bed reactor (FBR). The FBR was continuously operated as a unit for the removal of nitrogen from the effluents of domestic sewage treatment plant, with an additional supply of methanol as a carbon source. By denaturing gradient gel electrophoresis (DGGE) and sequence analysis of 16S ribosomal RNA genes, Thauera group was found to be dominant among the denitrifying bacteria in the FBR sludge. Oligonucleotide probe THA155 for fluorescence in situ hybridization (FISH) was newly designed for specifically targeting the Thauera group. However, the THA155 signal obtained from the sludge was only 0.9–5.7% of the DAPI-stained total cells. The real-time polymerase chain reaction (PCR) targeting the sequences of nitrite reductase (NIR) gene, a key enzyme of denitrification processes, was performed to quantify the cells of denitrifying bacteria cells including the Thauera group in FBR sludge. An excellent correlation was obtained between the numbers of nirS genes and the activity of denitrifiers in the FBR sludge.
International standards for services activities relating to drinking water supply systems and wastewater systems: Implications for developing countries
Authors: Lee S. , Cha D. , Park H.
Published: July 2007

In developing countries, the PPP (Public–Private–Partnerships) programs have been unsatisfied during the last decade. This study analyzed one of the main causes is low quality of the system. That is, no matter what supports developing countries may get through PPP, reforming water systems can be hardly successful without appropriate system quality. With this background, this study introduces service standards of ISO/TC 224 as an option to improve system quality of developing countries. To analyze its effects, system dynamic modeling was conducted. The results indicated that service standards, working with the PPP programs, can benefit all the stakeholders involved in the water systems in developing countries. Also this indicates further that this approach with service standards deserves more detailed study for improving the ailing water systems in developing countries.
The effect of Fe(0) on electrokinetic remediation of clay contaminated with perchloroethylene
Authors: Yuan C.
Published: July 2007

The present paper was to investigate the effect of Fe(0) reaction barrier position and Fe(0) quantity on the remediation efficiency and electrokinetic performances of tetrachloroethylene (PCE) contaminated clay under potential gradient of 2 V/cm for 5 days. The Fe(0) reaction barrier was composed of 2∼16 g of Fe(0) mixed with Ottawa sand in a ratio of 1 : 2. Its positions were respectively located at the anode, the middle, and the cathode end of the electrokinetic cell. Results showed that a relatively higher remediation of 66% of PCE was found as the Fe(0) reaction barrier located at the cathode side, which corresponded to a factor 2.4 times greater than that in the EK system alone (27.0%). As the Fe(0) quantity increased to 16 g, a highest remediation efficiency of 90.7% was found. It was concluded that the PCE removal in the EK/Fe(0) system was dominated by Fe(0) quantity rather than the Fe(0) reaction barrier position. As more Fe(0) existed in the EK system, a higher electroosmosis flow, higher permeability, and lower soil pH after treatment were found. The cost analyses were also investigated in this research.
Low strength wastewater treatment under low temperature conditions by a novel sulfur redox action process
Authors: Yamaguchi T. , Bungo Y. , Takahashi M. , Sumino H. , Nagano A. , Araki N. , Imai T. , Yamazaki S. , Harada H.
Published: July 2007

The objective of this research is to make a novel wastewater treatment process activated by a sulfur-redox cycle action of microbes in low temperature conditions. This action is carried out by sulfate-reducing bacteria (SRB) and sulfur-oxidizing bacteria (SOB). The process was comprised of a UASB reactor as pre-treatment and an aerobic downflow hanging sponge (DHS) reactor as post-treatment. As the results of reactor operation, the whole process achieved that over 90% of CODcr removal efficiency, less than 30 mgCODcr/L (less than 15 mgBOD/L) of final effluent, at 12 h of HRT and at 8 °C of UASB reactor temperature. Acetobacterium sp. was detected as the predominant species by PCR-DGGE method targeting 16SrDNA with band excision and sequence analysis. In the UASB reactor, various species of sulfate-reducing bacterium, Desulfobulbus sp., Desulfovibrio sp., and Desulfomicrobium sp., were found by cloning analysis. In the DHS reactor, Tetracoccus sp. presented as dominant. The proposed sulfur-redox action process was considered as an applicable process for low strength wastewater treatment in low temperature conditions.
Evaluation of a long-term operation of a submerged nanofiltration membrane bioreactor (NF MBR) for advanced wastewater treatment
Authors: Choi J.-H. , Fukushi K. , Ng H.Y. , Yamamoto K.
Published: July 2007

Nanofiltration (NF) is considered as one of the most promising separation technologies to obtain a very good-quality permeate in water and wastewater treatment. A submerged NF membrane bioreactor (NF MBR) using polyamide membranes was tested for a long-term operation and the performance of the NF MBR was compared with that of a microfiltration MBR (MF MBR). Total organic carbon (TOC) concentration in the permeate of the NF MBR ranged from 0.5 to 2.0 mg/L, whereas that of the MF MBR showed an average of 5 mg/L. This could be explained by the tightness of the NF membrane. Although the concentration of organic matter in the supernatant of the NF MBR was higher than that in the permeate due to high rejection by the NF membrane, the NF MBR showed excellent treatment efficiency and satisfactory operational stability for a long-term operation.
New ORP/pH based control strategy for chlorination and dechlorination of wastewater: pilot scale application
Authors: Kim H. , Kwon S. , Han S. , Yu M. , Kim J. , Gong S. , Colosimo M.F.
Published: July 2007

Due to its efficiency and low capital demands, chlorination has been widely used for disinfection in many wastewater treatment plants. Since the oxidation power of free chlorine is bigger than combined chlorines which are formed from the reaction between chlorine and reducing agents in water (especially, NH4+ and organic nitrogen), for effective disinfection, excess amount of chlorine is added until all the reducing agents are oxidized and free chlorine is available. After chlorination, chlorine residues in wastewater are usually reduced with SO2 or sulfites before the treated wastewater is discharged, since they are toxic to aquatic life. Addition of excess amount of SO2 or sulfite should be avoided. Otherwise, they consume dissolved oxygen in a river or stream and may have adverse impact on the aquatic life. Determination of wastewater chlorine demand and of sulfite dosages for dechlorination has been a challenge to WWTP operators, due to the dynamic characteristics of wastewater. Recently, a new ORP/pH based approach to determine chlorine demand and sulfite dosage was proposed. The method utilizes significant points occurring on the pH and ORP profiles during chlorination and dechlorination titrations. In this study, the proposed automatic titration system has been implemented into a control system to optimize chlorine and sulfite doses for a pilot scale chlorination/dechlorination system. In short, the disinfection system with the pH/ORP based controller showed very successful results; complete inactivation of total coliforms, and almost zero residual chlorines and high DO in its effluent.
Biodegradation of a variety of bisphenols under aerobic and anaerobic conditions
Authors: Ike M. , Chen M.Y. , Danzl E. , Sei K. , Fujita M.
Published: July 2007

There is a group of compounds structurally similar to bisphenol-A (BPA), namely bisphenols (BPs), and some of them are considered to be able to partially replace BPA. In order to assess their biodegradability in the aquatic environment, a variety of BPs; BPA, bis(4-hydroxyphenyl)methane (BPF), bis(4-hydroxyphenyl)ethane (BPE), 2,2-bis(4-hydroxy-phenyl)butane (BPB), 2,2-bis(4- hydroxy-3-methylphenyl)propane (BPP), bis(4-hydroxyphenyl)sulfone (BPS), thiodiphenol (TDP) and 4,4′-dihydroxybenzophenone (HBP); were subjected to biodegradation tests under both aerobic and anaerobic conditions. For the aerobic degradation test, a kind of river-die-away method using several river water samples was used, while pond sediments were used for the anaerobic degradation tests in sealed anoxic bottles. As a whole, the examined BPs could be ranked by their biodegradability under aerobic conditions; BPF, HBP >> BPA > BPP > BPE > BPB > TDP >> BPS. On the other hand, the tendency for the anaerobic biodegradability was; BPF > HBP > BPS, BPA, TDP > BPE > BPB. From the viewpoint of biodegradability, BPF seems to be more environmentally-friendly than BPA and, therefore, may be a candidate to replace BPA for reducing the environmental risks.
Polyhydroxyalkanoates (PHA) production using wastewater as carbon source and activated sludge as microorganisms
Authors: Yan S. , Tyagi R.D. , Surampalli R.Y.
Published: July 2007

Activated sludge from different full-scale wastewater treatment plants (municipal, pulp and paper industry, starch manufacturing and cheese manufacturing wastewaters) was used as a source of microorganisms to produce biodegradable plastics in shake flask experiments. Acetate, glucose and different wastewaters were used as carbon sources. Pulp and paper wastewater sludge was found to accumulate maximum concentration (43% of dry weight of suspended solids) of polyhydroxy alkanoates (PHA) with acetate as carbon source. Among the different wastewaters tested as a source of carbon, pulp and paper industry and starch industry wastewaters were found to be the best source of carbon while employing pulp and paper activated sludge for maximum accumulation of PHA. High concentration of volatile fatty acids in these wastewaters was the probable reason.
Parameter optimization and design aspect for electro- coagulation of silica nano-particles in wafer polishing wastewater
Authors: Den W. , Huang C.
Published: July 2007

A systematic procedure has been proposed for the design of a multi-channel, continuous-flow electrocoagulation reactor of mono-polar configuration for the removal of sub-micron particles from wastewater. Using the chemical–mechanical–planarization (CMP) process as the target source of wastewater, a series of laboratory-scale studies were conducted to determine the required operating conditions for the efficient removal of the ultrafine particles. These operating criteria included charge loading (≥8 F m−3), current density (≥5.7 A m−2), hydraulic retention time (≥60 min), as well as the initially operational pH (7∼10). Furthermore, a steady-state transport equation with second-order reaction kinetics was employed to describe the rate of coagulation as the rate-limiting factor. The actual kinetic constant determined from the laboratory-scale experiments was approximately 1.2 × 10−21 m3 s−1, which was three orders of magnitude smaller than that calculated based on Brownian diffusion during the coagulation.The model was subsequently validated with a series of experiments using a pilot-scale electro-coagulation reactor geometrically similar to the laboratory-scale reactor with nearly twenty times volumetric scale-up.
Solutions to a combined problem of excessive hydrogen sulfide in biogas and struvite scaling
Authors: Charles W. , Cord-Ruwisch R. , Ho G. , Costa M. , Spencer P.
Published: July 2007

The Woodman Point Wastewater Treatment Plant (WWTP) in Western Australia has experienced two separate problems causing avoidable maintenance costs: the build-up of massive struvite (MgNH4PO4· 6H2O) scaling downstream of the anaerobic digester and the formation of hydrogen sulfide (H2S) levels in the digester gas to levels that compromised gas engine operation and caused high operating costs on the gas scrubber. As both problems hang together with a chemical imbalance in the anaerobic digester, we decided to investigate whether both problems could be (feasibly and economically) addressed by a common solution (such as dosing of iron solutions to precipitate both sulfide and phosphate), or by using separate approaches. Laboratory results showed that, the hydrogen sulfide emission in digesters could be effectively and economically controlled by the addition of iron dosing. Slightly higher than the theoretical value of 1.5 mol of FeCl3 was required to precipitate 1 mol of dissolved sulfide inside the digester. Due to the high concentration of PO43− in the digested sludge liquor, significantly higher iron is required for struvite precipitation. Iron dosing did not appear an economic solution for struvite control via iron phosphate formation. By taking advantage of the natural tendency of struvite formation in the digester liquid, it is possible to reduce the risk of struvite precipitation in and around the sludge-dewatering centrifuge by increasing the pH to precipitate struvite out before passing through the centrifuge. However, as the Mg2+ /PO43− molar ratio in digested sludge was low, by increasing the pH alone (using NaOH) the precipitation of PO43− was limited by the amount of cations (Ca2+  and Mg2+ ) available in the sludge. Although this would reduce struvite precipitation in the centrifuge, it could not significantly reduce PO43− recycling back to the plant. For long-term operation, maximum PO43− reduction should be the ultimate aim to minimise PO43− accumulation in the plant. Magnesium hydroxide liquid (MHL) was found to be the most cost-effective chemical to achieve this goal. It enhanced struvite precipitation from both, digested sludge and centrate to the point where more than 95% PO43− reduction in the digested sludge was achieved.
Effect of a suspended carrier on membrane fouling in a submerged membrane bioreactor
Authors: Wei Chun-Hai , Huang Xia , Wang Cheng-Wen , Wen Xiang-Hua
Published: July 2007

In an attempt at membrane fouling control, a kind of cylindrical plastic suspended carrier was added in a submerged membrane bioreactor (SMBR) and its effect was investigated in this study. According to the transmembrane pressure (TMP) profiles and the sludge characteristics in comparative runs with and without suspended carriers, it was found that the suspended carriers added in SMBR had two effects on membrane fouling: one was the positive effect of mechanically scouring the membrane surface and the other was the negative effect of breaking up sludge flocs. Sludge particle size distribution change was mainly responsible. It was suggested to apply the suspended carrier at higher MLSS concentration and lower carrier dose based on the consideration for retarding sludge breakage caused by the carrier. The experiment was conducted under higher MLSS (8 g L−1) and lower carrier dose (carrier volume/total volume = 1%). The TMP increase was effectively retarded by added suspended carriers compared to the system without addition of the carriers. The effect of suspended carriers on membrane fouling at high MLSS concentration was verified.
Particle size distribution to design and operate an APT process for agricultural wastewater reuse
Authors: Chavez A. , Maya C. , Jimenez B.
Published: July 2007

Total suspended solids is a parameter commonly used to operate and design coagulation–flocculation processes. Nevertheless, their application for an advanced primary treatment (a high performance but low dose demand coagulation processes coupled with a high rate sedimentator, sometimes called enhanced primary treatment) is not the best option to produce an effluent for agricultural irrigation. This paper compares the best operating conditions obtained using the TSS or the PSD (particle size distribution) as parameters to follow the efficiency. The treatment objective was to remove particles >20 μm, in such conditions that the effluent can contain organic matter and nutrients necessary for crops with a reduced number of helminth ova (with sizes between 20 to 80 μm). Using the TSS as parameter, the best coagulation (460 s−1, 60 s contact time and 300 μmolAl/L) and flocculation (20 s−1 with 15 min) conditions produced an effluent with 1.2 HO/L. To obtain a similar results but using operating conditions determined with the PSD at a three times lower coagulant dose can be employed (diminishing operating costs and reducing the quantity of sludge produced), and a reduction on energy consumption of around eight times can be reached. Best operating conditions defined using the PSD (160 s−1, 60 s contact time and 100 μmolAl/L) produced an effluent with <0.4 HO/L.
Wastewater dissolved organic matter: characteristics and sorptive capabilities
Authors: Chefetz B. , Ilani T. , Schulz E. , Chorover J.
Published: July 2007

An evaluation of the mobility of organic pollutants with wastewater dissolved organic matter (DOM) is essential to better understanding their fate and toxicity to the environment. In this study, DOM from two wastewater treatment plants (in Lachish and Netanya, Israel) were fractionated to hydrophobic-acid (HoA) and hydrophobic-neutral (HoN) fractions. The fractions were characterised and their sorptive capabilities for s-triazine herbicides and polycyclic aromatic hydrocarbons (PAHs) were studied. For all sorbates, binding to the HoN fractions was much higher than to HoA fractions. The high binding coefficients obtained for the studied triazines by the HoN fractions suggested that their sorption is governed by hydrophobic-like interactions rather than H-bonding. The binding coefficients of PAHs measured for the HoN fractions were within the range reported for humic acids and much higher than for the HoA fraction, suggesting that the HoN fraction plays an important role in the overall sorption of these compounds by DOM. Higher sorption coefficients were measured for the Netanya DOM sample containing a higher level of hydrophobic fractions (HoA + HoN) than the Lachish DOM, suggesting that the sorption of hydrophobic organic compounds by DOM is governed by the relative content of these structural substances.
Coagulation of NOM: linking character to treatment
Authors: Sharp E.L. , Parson S.A. , Jefferson B.
Published: July 2007

The paper presents an overview and discussion on the link between natural organic matter (NOM) character and its treatability by coagulation. Trials were conducted on a series of bench scale and pilot plant trials on three source waters: two from UK moorland catchments and one from a US snow melt source. Overall the work demonstrates the importance of the polarity balance and the charge density of the NOM contained within the source water. The hydrophobic content controls the coagulant demand such that variation in the demand between sources or sampling periods can be accounted for by changes in the hydrophobic content and its charge density. The raw water hydrophilic content, and specifically the nonacid fraction, provides a useful indicator of the achievable residual. Analysis of coagulation performance revealed a clear relationship between zeta potential and residual DOC. For each source an operational zeta potential range exists within which the residual concentration is optimal. Comparison of the ranges achieved during each trial demonstrated that a communal range between −10 and +3 mV exist for all waters thus providing a useful guide range for operational control.
The effect of polymeric flocculants on floc strength and filter performance
Authors: Rawlings M.M. , Fitzpatrick C.S.B. , Gregory J. , Wetherill A.
Published: July 2007

Polymeric flocculants are widely used throughout the water industry as flocculant aids, they are known to increase floc density and aid settlement in the clarification stage of the water treatment process. In this research, polymeric flocculants were used to improve floc strength prior to filtration on a dissolved air flotation (DAF) plant in an attempt to prevent filter breakthrough. A modified jar test procedure using a PDA (photometric dispersion analyser) optical flocculation monitor was developed in order to evaluate the system floc strength. Filtration trials were carried out on a pilot filter rig situated on a surface water treatment works in Yorkshire. The filter feed originated from the main plant filter channel. Filter performance was assessed by continuous online monitoring of effluent particle counts, turbidity and headloss over the period of the filter run. Results indicated that low doses of polymeric flocculants had a beneficial effect on filtered water quality, as measured by particle counts, turbidity, UV254 absorption and dissolved organic carbon (DOC). Polymeric flocculants also had the effect of extending filter run length. The modified jar test results indicated that the flocculants used improved the floc strength and enhanced reflocculation of the micro flocs present after the flotation process.
Settling characteristics of problem algae in the water treatment process
Authors: Choi S.K. , Lee J.Y. , Kwon D.Y. , Cho K.J.
Published: July 2007

The settling velocity or removal rates of problem algae in the water treatment process and their flocculants were measured with settling column (SETCOL) and fluorometric method. Our research who were centred on the algal density and shape affecting the settling. The settling velocities of large algae ranged from 0.1 cm/h to 2.6 cm/h, whereas those of small algae were below 1.0 cm/h. The settlings of algae in the stationary growth phase significantly increased and dead algae corresponded with the declining algae. The extent of deformation, which was expressed as the coefficient of form resistance of the algae had the great influences upon the settling. The most extreme deformed algae were needle-shaped ones like Synedra acus, which was known to be a problem in water treatment processes in Korea. Changes in the settling velocity of algae were correlated with algal volume and morphology rather than cell density.
Effects of surface charge, micro-bubble size and particle size on removal efficiency of electro-flotation
Authors: Han M.Y. , Kim M.K. , Ahn H.J.
Published: July 2007

Flotation is a water treatment alternative to sedimentation, and uses small bubbles to remove low-density particles from potable water and wastewater. The effect of zeta potential, bubble size and particle size on removal efficiency of the electro-flotation process was investigated because previous model-simulations indicated that these attributes are critical for high collision efficiency between micro-bubbles and particles. Solutions containing Al3 +  as the metal ion were subjected to various conditions. The zeta potentials of bubbles and particles were similar under identical conditions, and their charges were influenced by metal ion concentration and pH. Maximum removal efficiency was 98 and 12% in the presence and absence of flocculation, respectively. Removal efficiency was higher when particle size was similar to bubble size. These results agree with modelling simulations and indicate that collision efficiency is greater when the zeta potential of one is negative and that of the other is positive and when their sizes are similar.
Pretreatment chemistry for dual media filtration: model simulations and experimental studies
Authors: Shin J.Y. , O'Melia C.R.
Published: July 2007

Laboratory dual media filtration experiments were conducted (a) in direct filtration mode using model raw water moderate in turbidity and low in DOC, and (b) in conventional filtration mode treating water moderate in turbidity and high in DOC. Model simulations of filter performance for the removal of particles provided hypotheses for the experimental studies of dual media filtration. An increase in alum dose in direct filtration mode, while improving filter performance, also showed some disadvantages, including rapid development of head loss. Suboptimal dose in direct filtration significantly impaired the filter performance. In conventional mode, the effect of alum dose on the filter performance, while obvious, was not as dramatic as in direct filtration. Ripening indicated by particle counts occurred earlier than by turbidity and breakthrough of particle counts started earlier than breakthrough of turbidity, suggesting that turbidity can be used as a more conservative monitor of filter performance during the ripening period to minimise the risk of passage of small particles, while particle counts can be considered a more sensitive indicator of deteriorating filter performance during the breakthrough period. The lower sand layer served as a multiple barrier for particles when the performance of the anthracite layer was not effective.
A high filtration system with synthetic permeable media for wastewater reclamation
Authors: Park K.Y. , Maeng S.K. , Kim K. , Kweon J.H. , Ahn K.H.
Published: July 2007

A novel filtration process with synthetic permeable media was investigated for secondary effluent reclamation. Polyurethane was chosen as the filter medium among three tested media. Compressibility and up-flow velocity were changed to determine the optimum operation for the system. An equation was introduced to express the relationship between the removal efficiency and up-flow velocity. In a pilot study, the synthetic medium filtration with compression showed very stable effluent quality without clogging trouble, though the system operated with three times higher filtration rate and much longer backwashing interval than conventional systems.
Effects of flocculent aggregates on microfiltration with coagulation pretreatment of high turbidity waters
Authors: Lee S. , Kweon J. H. , Choi Y. H. , Ahn K.-H.
Published: July 2007

Immersed membrane systems, and those with in-line coagulation, have been extensively applied in drinking water systems. Sedimentation is usually replaced by membrane processes in both systems. In these systems, voluminous flocculent aggregates formed during coagulation could be potential foulants. When raw waters with high turbidity are introduced, particle loadings to membrane due to coagulation pretreatment are enormous and thus could increase fouling. In general, during the rainy season, the turbidity of the Han River water, which supplies drinking water for the City of Seoul, Korea, is more than a hundred times higher than usual. Therefore, effects of floc on membrane fouling were investigated with highly turbid waters. Two turbidity concentrations, 40 and 200 NTU, were formulated by the addition of kaolin (used as a natural particle surrogate) to the Han River raw water. The results showed that the flux decline behaviours of the highly turbid waters were different from those of natural raw water. Coagulation pretreatment was very effective at reducing membrane fouling. Flocculent aggregates showed a negative effect on the flux decline, but a positive effect on the membrane cleaning efficiency.
Characteristics of sludge reduction in an integrated pretreatment and aerobic digestion process
Authors: Hwang S. , Jang H. , Lee M. , Song J. , Kim S.
Published: July 2007

In this study, integrated pretreatments and aerobic digestion processes were investigated in order to provide a feasible alternative that can achieve effective sludge reduction. An ozone treatment in the presence of ionic manganese, a catalyst, increased the sludge reduction ratio three times higher than that of a single ozonation, presumably due to an increase in OH radical production. The ozone treatment yielded the effective sludge reduction ratio with an increasing ozone dosage, and an effective dosage of the catalyst was found to be 4 mg-Mn/g-TS. When a mechanical pretreatment and an ozone/catalyst were applied in a series, the integrated process, even at a half mechanical intensity and a half level of ozone dosage, showed higher and faster sludge reduction than each single process did. In addition, the integrated pretreatment process showed the highest dewaterability of the treated sludges. A ratio of sludge cake generation, which was newly introduced to quantify overall performance of sludge treatment processes, showed that the integrated pretreatment followed by the aerobic digestion yielded approximately a half of the sludge cake volume compared to the single aerobic digestion. Therefore, the integrated pretreatment can be a feasible method for the effective reduction of total suspended solid and the final volume.
Particle separation options for emergency water treatment
Authors: Dorea C.C. , Bertrand S. , Clarke B.A.
Published: July 2007

Emergencies can result from the effects of unpredictable natural forces or from the cruelty of conflicts. The affected population is often left vulnerable to increased health risks. The victims' exposure to these risks can be reduced by timely public health interventions. Often, one of the first basic mitigations is the provision of water for essential needs. The quickest option, and generally more polluted, is of surface waters. We have reviewed particle separation options for emergency water treatment of surface waters. These vary from granular filtration package treatment facilities to ceramic candle filters and have therefore been broadly classified in three categories: modular, mobile and point-of-use (or household). The operational requirements and process limitations that can influence the choice of each option are discussed alongside with their underlying particle separation mechanisms and performance data.
Methane production and solids destruction in an anaerobic solid waste reactor due to post-reactor caustic and heat treatment
Authors: DiStefano T.D. , Ambulkar A.
Published: July 2007

This study was undertaken to determine the feasibility of caustic and heat treatment of sludge from a dry anaerobic reactor (DAR) with respect to increased methane production and solids destruction. The DAR was operated semi-continuously at 55 °C on sized-reduced municipal solid waste at a solids retention time of 15 days. A respirometer was employed to monitor the extent and rate of methane production from anaerobic biodegradation of DAR sludge that was treated with caustic and heat. Results indicate that caustic and heat treatment at 50 °C and 175 °C increased methane production by 22% and 52%, respectively. Also, volatile solids destruction increased from 46% to 58% and 83%, respectively. Based on these results, economic analysis for a full-scale 105 kg/d facility suggests that annual project revenue for 50 °C and 175 °C treatment is estimated at $21,000 and $445,000, respectively.
Prion protein: detection in ‘spiked’ anaerobic sludge and degradation experiments under anaerobic conditions
Authors: Kirchmayr R. , Reichl H.E. , Schildorfer H. , Braun R. , Somerville R.A.
Published: July 2007

The behavior of the transmissible spongiform encephalopathies (TSE) causing agent denominated “prion protein” in anaerobic sludge (biogas reactor) was assessed with incubation tests. A widely applied screening method for BSE in cattle on the basis of the Western blotting protocol was adapted to detect the Proteinase K resistant, scrapie-form prion protein (PrPSC). As PrPSC source homogenized TSE infected brain tissue of animals late in the clinical phase of disease was taken (301V/VM mouse-BSE; bovine BSE and 22A/SV mouse-scrapie). The incubation under mesophilic conditions did not show any significant reduction of the PrPSC titer. Under thermophilic conditions contradictory results were obtained. The reduction time of PrPSC in water was equal to or longer than the PrPSC reduction time in anaerobic sludge. In comparison, with sterilized (121 °C, steam pressure) or poisoned (sodium azide, 1% w/v) sludge used as incubation matrix a much shorter time resulted until no prion protein could be detected.
Comparison between the conventional anaerobic digestion of sewage sludge and its combination with a chemical or thermal pre-treatment concerning the removal of pharmaceuticals and personal care products
Authors: Carballa M. , Omil F. , Alder A.C. , Lema J.M.
Published: July 2007

Many novel treatment technologies, usually representing a pre-treatment prior to the biological degradation process, have been developed in order to improve the recycling and reuse of sewage sludge. Among all the methods available, a chemical (alkaline) and a thermal treatment have been considered in this study. The behaviour of 13 substances belonging to different therapeutic classes (musks, tranquillisers, antiepileptic, anti-inflammatories, antibiotics, X-ray contrast media and estrogens) has been studied during the anaerobic digestion of sewage sludge combined with these pre-treatments (advanced operation) in comparison with the conventional process. Two parameters have been analysed: the temperature (mesophilic and thermophilic conditions) and the sludge retention time. While organic matter solubilization was higher with the alkaline process (55–80%), no difference between both pre-treatments was observed concerning volatile solids solubilization (up to 20%). The removal efficiencies of solids and organic matter during anaerobic digestion ranged from 40–70% and 45–75%, respectively. The higher removal efficiencies of pharmaceuticals and personal care products were achieved for the antibiotics, Naproxen and the natural estrogens (>80%). For the other compounds, the values were in the range 20–70%, except for Carbamazepine, which was not removed at any condition tested.
Phthalate hydrolysis under landfill conditions
Authors: Jonsson S. , Vavilin V.A. , Svensson B.H.
Published: July 2007

Experimental data from a study using a landfill simulation reactor were used to develop and calibrate a one-dimensional distributed model of co-digestion of municipal solid waste and three phthalic acid diesters with different water solubilities. The three diesters were diethyl phthalate, dibutyl phthalate, and di-2-ethylhexyl phthalate. Two types of municipal solid wastes were assumed, easily degradable and recalcitrant. The model considered inhibition of hydrolysis of the recalcitrant fraction and phthalic acid esters, and also methanogenesis at acidic pH. The results indicated that the prolonged steady-state concentrations of the diesters in the leachates could be explained by equilibrium between physicochemical desorption and sorption processes for the three diesters. When methanogenic conditions were induced in the acidogenic landfill simulation reactor, inhibition of both hydrolysis of recalcitrant MSW and of phthalic acid esters ceased.
Two-stage thermophilic-mesophilic anaerobic digestion of waste activated sludge from a biological nutrient removal plant
Authors: Watts S. , Hamilton G. , Keller J.
Published: July 2007

A two-stage thermophilic-mesophilic anaerobic digestion pilot-plant was operated solely on waste activated sludge (WAS) from a biological nutrient removal (BNR) plant. The first-stage thermophilic reactor (HRT 2 days) was operated at 47, 54 and 60 °C. The second-stage mesophilic digester (HRT 15 days) was held at a constant temperature of 36–37 °C. For comparison with a single-stage mesophilic process, the mesophilic digester was also operated separately with an HRT of 17 days and temperature of 36–37 °C. The results showed a truly thermophilic stage (60 °C) was essential to achieve good WAS degradation. The lower thermophilic temperatures examined did not offer advantages over single-stage mesophilic treatment in terms of COD and VS removal. At a thermophilic temperature of 60 °C, the plant achieved 35% VS reduction, representing a 46% increase compared to the single-stage mesophilic digester. This is a significant level of degradation which could make such a process viable in situations where there is no primary sludge generated. The fate of the biologically stored phosphorus in this BNR sludge was also investigated. Over 80% of the incoming phosphorus remained bound up with the solids and was not released into solution during the WAS digestion. Therefore only a small fraction of phosphorus would be recycled to the main treatment plant with the dewatering stream.
Will anaerobic digestion of solid waste survive in the future?
Authors: De Baere L.
Published: July 2007

Anaerobic digestion has captured a significant share of the European market for the biological treatment of the organic fraction in municipal solid waste. Almost 4 million ton per year in digestion capacity has been installed through the construction of more than 120 full-scale plants. Not all plants have been equally successful, due to poor planning, design or bad operation. This, besides higher than expected investment and operating costs, may have slowed down the growth of anaerobic digestion of solid waste. However, an evaluation of the development of anaerobic digestion over the last 15 years shows that there is now a greater diversity in application, a wider range in types of systems and suppliers, and a continued increasing rate of implementation throughout most parts of Europe. New alternative treatment techniques have not seen the same level of success as anaerobic digestion. Anaerobic digestion has been established as a viable treatment technology for the organic fraction of municipal solid waste and will most likely play an even more important role in the future.
Anaerobic codigestion of waste activated sludge and OFMSW: the experiences of Viareggio and Treviso plants (Italy)
Authors: Bolzonella D. , Battistoni P. , Susini C. , Cecchi F.
Published: July 2007

The paper presents the results of two full-scale applications of the anaerobic co-digestion process of waste activated sludge together with the organic fraction of municipal solid wastes. The experiences were carried out at Viareggio and Treviso wastewater treatment plants (Italy). In the first plant, 3 tons per day of source sorted OFMSW were co-digested with waste activated sludge, increasing the organic loading rate from 1.0 to 1.2 kgTVS/m3d. This determined a 50% increase in biogas production. At Treviso WWTP, which has been working for 2 years, some 10 tons per day of separately collected OFMSW are treated using a low-energy consumption sorting line, which allows the removal of 99% and 90% of metals and plastics respectively. In these conditions, the biogas yield increased from 3,500 up to 17,500 m3/month. Industrial costs were evaluated less than 50 € per ton of organic waste, while the payback time was calculated as two years.
Mesophilic–thermophilic–mesophilic anaerobic digestion of liquid dairy cattle manure
Authors: Effenberger M. , Bachmaier J. , Garcés G. , Gronauer A. , Wilderer P.A. , Lebuhn M.
Published: July 2007

The potential of a mesophilic–thermophilic–mesophilic anaerobic digestion system was investigated with respect to improvement of both digestion and sanitation efficiencies during treatment of liquid cattle manure. The pilot plant produced a high methane yield from liquid dairy cattle manure of 0.24 m3 (kg VSfed)−1. Considering the low system loading rate of 1.4–1.5 kg VS (m3 d)−1, digestion efficiency compared to conventional processes did not appear improved. The minimum guaranteed retention time in the tubular thermophilic reactor was increased compared to a continuously stirred tank reactor. Levels of intestinal enterococci in raw liquid manure as determined with cultivation methods were reduced by 2.5–3 log units to a level of around 102 cfu/mL. This sanitizing effect was achieved both during mesophilic–thermophilic–mesophilic and thermophilic–mesophilic treatment, provided the thermophilic digester was operated at 53–55°C. A change in feeding interval from 1 h to 4 h did not significantly alter methane yield and sanitation efficiency. It was proposed that a two-stage, thermophilic–mesophilic anaerobic digestion system would be able to achieve the same sanitizing effect and equal or better digestion efficiency at lower costs.
Effects of solids concentration, pH and carbon addition on the production rate and composition of volatile fatty acids in prefermenters using primary sewage sludge
Authors: Zeng R.J. , Yuan Z. , Keller J.
Published: July 2007

Increasing evidence is emerging that the performance of enhanced biological phosphorus removal (EBPR) systems relies on not only the total amount but also the composition of volatile fatty acids (VFAs). Domestic wastewater often contains limited amounts of VFAs with acetic acid typically being the dominating species. Consequently, prefermenters are often employed to generate additional VFAs to meet the demand for carbon by EBPR and/or denitrification processes. Limited knowledge is currently available on the effects of operational conditions on the production rate and composition of VFAs in prefermenters. In this study, a series of controlled batch experiments were conducted with sludge from a full-scale prefermenter to determine the impact of solids concentration, pH and addition of molasses on prefermentation processes. It was found that an increase in solids concentration enhanced total VFA production with an increased propionic acid fraction. The optimal pH for prefermentation was in the range of 6–7 with significant productivity loss when pH was below 5.5. Molasses addition significantly increased the production of VFAs particularly the propionic acid. However, the fermentation rate was likely limited by the biological activity of the sludge rather than by the amount of molasses added.
Thermophilic anaerobic fermentation of olive pulp for hydrogen and methane production: modelling of the anaerobic digestion process
Authors: Gavala H.N. , Skiadas I.V. , Ahring B.K. , Lyberatos G.
Published: July 2007

The present study investigates the thermophilic biohydrogen and methane production from olive pulp, which is the semi-solid residue coming from the two-phase processing of olives. It focussed on: a) production of methane from the raw olive pulp; b) anaerobic bio-production of hydrogen from the olive pulp; c) subsequent anaerobic treatment of the hydrogen-effluent with the simultaneous production of methane; and d) development of a mathematical model able to describe the anaerobic digestion of the olive pulp and the effluent of hydrogen producing process. Both continuous and batch experiments were performed. The hydrogen potential of the olive pulp amounted to 1.6 mmole H2 per g TS. The methane potential of the raw olive pulp and hydrogen-effluent was as high as 19 mmole CH4 per g TS suggesting that: a) olive pulp is a suitable substrate for methane production; and b) biohydrogen production can be very efficiently coupled with a subsequent step for methane production.
Oestrogen removal from biological pretreated wastewater within decentralised sanitation and re-use concepts
Authors: de Mes T.Z.D. , Urmenyi A.M. , Poot A.A. , Wessling M. , Mulder M.H.V. , Zeeman G.
Published: July 2007

Two parallel researches were performed; one focused on the fate of oestrogens in the biological treatment systems within decentralised sanitation and re-use concepts (DESAR), the second related to the development of a suitable specific removal method. A new affinity membrane was developed using antibodies as specific binding sites for hormone removal. It was found that, especially in anaerobic treatment, the core technology in DESAR, the removal is insufficient and therefore an additional separation method is required. The affinity membrane with antibodies was found to be a suitable additional method, though in the current system it only removes one selected compound. Future research will focus on making this method more feasible in practise.
A dispersed-ozone flotation (DOF) separator for tertiary wastewater treatment
Authors: Jin P.K. , Wang X.C. , Hu G.
Published: July 2007

A dispersed-ozone flotation (DOF) separator was devised for a pilot study of tertiary wastewater treatment for re-use purposes. As a compact device combining coagulation, ozonation and flotation in an integrated unit, the DOF separator achieved a very high removal of SS, TOC, UV254 and colour, as well as effective inactivation of coliform and total bacteria within a short hydraulic retention time of 30 min. The finished water quality is comparable to or better than that by a conventional tertiary treatment process using coagulation, sedimentation, filtration and chlorine disinfection, and meets the quality standards for non-drinkable domestic reuse.
Safety of treated water for re-use purposes – comparison of filtration and disinfection processes
Authors: Wang X.C. , Qiu F.G. , Jin P.K.
Published: July 2007

A study was conducted on the distribution of pollutants in treated wastewater and the its safety for re-use purposes. Based on the results of a series of tertiary treatment experiments, the effects of three filtration processes, i.e. coagulation-filtration, ozonation-biological activated carbon filtration (O3-BAC) and ultrafiltration (UF), and two chemical disinfection processes, i.e. chlorination and ozonation, on the safety of water re-use were evaluated. It was found that the concentrations of the main pollutants in the secondary effluent and further filtered water follow a log-normal distribution and, therefore, a log-normal probabilistic function can be used to evaluate the suitability of the treated water for re-use purposes. Among the three filtration processes evaluated, UF is the most effective in turbidity removal but less effective in colour and COD removal, while coagulation-filtration and O3-BAC can ensure a good removal of all these pollutants. Regarding chemical disinfection, although chlorine is very effective in inactivation of coliform bacteria, it can not achieve a substantial decrease in viruses. As ozone is applied, effective virus removal can be achieved.
Anaerobic uptake of phosphate in an anaerobic–aerobic granular sludge sequencing batch reactor
Authors: Wang X. , Ji M. , Wang J.F. , Liu Z. , Yang Z.Y.
Published: July 2007

An unusual phenomenon of anaerobic phosphate uptake under alternating anaerobic/aerobic condition was observed in a granular sludge sequencing batch reactor, fed with acetate as sole organic substrate. Anaerobic phosphate uptake efficiencies remained at 50–70% as the influent P/COD was increased from 2/100 to 4/100, and results showed that anaerobic uptake of phosphate was correlated with anaerobic absorption of acetate. Excluding the main possibility of chemical phosphate removal, it appeared that phosphate uptake during the anaerobic phase was associated with organisms enriched in the reactor. Moreover, results indicated that intracellular glycogen was used as the main energy source of organics anaerobic absorption and intracellular polymers storage. Measuring and analysing the variation of phosphate, organic substrate, intracellular glycogen and pH in the anaerobic phase, a preliminary explanation was developed that anaerobic uptake of phosphate was the demand of intracellular glycogen degradation, and extracellular phosphate was transported to intracellular by pH gradient-sensitive phosphate carrier protein.