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This paper presents a gas chromatography-mass spectrometry method for simultaneous detection of five selected phenolic xenoestrogens. These include 4,4’-biphenyldiol (4,4’-dihydroxybiphenyl), 3-hydroxybiphenyl (m-phenylphenol), and 6-bromo-2-naphthol. In each analysis, one liter of water sample was extracted by using solid phase extraction (SPE) method. A simple and yet reliable derivatization reagent (i.e. trimethylphenylammonium hydroxide solution) was used in this study to enhance detection sensitivity. The method detection limits of the proposed method for the selected phenolic xenoestrogens were found to fall within the range of 2.3 to 12.4 ng L−1. Results of recovery tests showed that recoveries of the selected phenolic xenoestrogens in deionized water were within the range of 64% to 88% with relative standard deviations of 4% to 17% (n=10), when spiked with 100 and 500 ng L−1 of standards. The corresponding results for the fortified treated wastewater samples were 69% to 87% and 5% to 12% (n=7), respectively. The proposed method was successfully applied for detecting the selected xenoestrogens in tap water, treated wastewater and fortified deionized water. It was noted that the target compounds, at low ng L−1 levels, could be detected in treated wastewater samples.

The RNA F-specific coliphages, MS2 and Qbeta, have been used as virus indicators in water and wastewater studies. It is therefore useful to have a good understanding concerning the effects of environmental factors on their survival in order to choose an appropriate candidate for assessing microbial safety in relation to water quality management. The effects of pH and temperature on the survival of these two coliphages were investigated. MS2 survived better in acidic conditions than in an alkaline environment. In contrast, Qbeta had a better survival rate in alkaline conditions than in an acidic environment. The inactivation rates of both coliphages were lowest within the pH range 6-8 and the temperature range 5-35 degrees C. The inactivation rates of both coliphages increased when the pH was decreased to below 6 or increased to above 8. The inactivation rates of both coliphages increased with increasing temperature. Qbeta behaved peculiarly in extreme pH buffers, i.e. it was inactivated very rapidly initially when subjected to an extreme pH environment, although the inactivation rate subsequently decreased. In general, MS2 was a better indicator than Qbeta. However, within the pH range 6-9 and at temperatures not above 25 degrees C, either MS2 or Qbeta could be used as a viral indicator.

The production rate of permeate in a reverse osmosis (RO) process controlled by mass transfer is proportional to the net driving pressure and the total membrane surface area. This linear relationship may not be the only mechanism controlling the performance of a full-scale membrane process (typically a pressure vessel holding six 1-m-long modules in series) which utilizes highly permeable membranes. The mechanisms that control the performance of an RO process under various conditions were carefully examined in this study. It was demonstrated that thermodynamic equilibrium can impose a strong restriction on the performance of a full-scale RO process under certain circumstances. This thermodynamic restriction arises from the significant increase in osmotic pressure downstream of an RO membrane channel due to the accumulation of rejected salt within the RO channel as a result of permeate water production. Concentration polarization is shown to have a weaker influence on the full-scale RO process performance than the thermodynamic restriction. The behavior of the process under thermodynamic restriction is quite different from the corresponding behavior that is controlled by mass transfer. The transition pressure for an RO process to shift from a mass transfer controlled regime to a thermodynamically restricted regime was determined by the basic parameters of the full-scale RO process.

Removals of MS2 bacteriophage virus using different membrane materials under different operating pressures were investigated. The results obtained in this study suggested that a better log removal in terms of MS2 bacteriophage virus could be achieved using Polyamide RO membrane under the optimum operating pressure of 100 psi. It is further noted that variable MS2 influent concentration levels resulted in corresponding variable log removals of the bacteriophages by the Polyamide RO membrane. The presence of MS2 bacteriophage virus in the effluent could possibly be due to leakage of bacteriophages through the membranes structure. Investigations using SEM and AFM showed that there were gaps or pores present in the membrane structure which were sufficiently large for the MS2 viruses to pass through.

The mechanisms controlling the performance of a full-scale reverse osmosis (RO) process (typically a pressure vessel holding six 1 m long modules in series) under various operating conditions are carefully examined in this study. We demonstrate that thermodynamic equilibrium imposes a strong restriction on the performance of a full-scale RO process under certain circumstances. This thermodynamic restriction arises from the significant increase in osmotic pressure downstream of an RO membrane channel (owing to the phenomenon of salt accumulation within the RO channel as a result of permeate production). The behavior of the full-scale RO process under thermodynamic restriction is much different from that of the process when it is controlled by mass transfer. The conditions for an RO process to shift from mass transfer-controlled regime to thermodynamically restricted regime are delineated and discussed.

The effects of cultivation temperature, aeration rate, and agitation speed on the production of β-mannanase by Bacillus licheniformis NK-27 in a batch fermenter were investigated in this study. Results revealed that temperature was the most significant factor in terms of its effect on β-mannanase production. It influenced β-mannanase production by affecting the other parameters including bacteria growth, pH, dissolved oxygen, total and reducing sugars. Agitation speed and aeration rate could affect dissolved oxygen concentration which in turn affected cell growth and β-mannanase production. A maximum β-mannanase activity of 212.0 U ml−1 was attained in 36 h of cultivation when aeration rate, agitation speed, and temperature were controlled at 0.75 vvm, 600 rpm, and 30 °C, respectively. The maximum β-mannanase activity in the fermenter was close to that obtained from the shake flask fermentation study (198.2 U ml−1). However, the duration of fermentation cycle in the fermenter study was shorter than the corresponding duration obtained from the shake flask experiment by 12 h.

N -acylhomoserine lactones (AHLs) are used as signal molecules by many quorum-sensing Proteobacteria. Diverse plant and animal pathogens use AHLs to regulate infection and virulence functions. These signals are subject to biological inactivation by AHL-lactonases and AHL-acylases. Previously, little was known about the molecular details underlying the latter mechanism. An AHL signal-inactivating bacterium, identified as a Ralstonia sp., was isolated from a mixed-species biofilm. The signal inactivation encoding gene from this organism, which we call aiiD , was cloned and successfully expressed in Escherichia coli and inactivated three AHLs tested. The predicted 794-amino-acid polypeptide was most similar to the aculeacin A acylase (AAC) from Actinoplanes utahensis and also shared significant similarities with cephalosporin acylases and other N-terminal (Ntn) hydrolases. However, the most similar homologues of AiiD are deduced proteins of undemonstrated function from available Ralstonia , Deinococcus and Pseudomonas genomes. LC-MS analyses demonstrated that AiiD hydrolyses the AHL amide, releasing homoserine lactone and the corresponding fatty acid. Expression of AiiD in Pseudomonas aeruginosa PAO1 quenched quorum sensing by this bacterium, decreasing its ability to swarm, produce elastase and pyocyanin and to paralyse nematodes. Thus, AHL-acylases have fundamental implications and hold biotechnological promise in quenching quorum sensing.

Endocrine disruptor contamination is an emerging issue of concern in the field of water quality engineering. In this study, a lab-scale microfiltration (MF) and reverse osmosis (RO) based water reclamation system was set up to monitor and evaluate the removal of bisphenol A (BPA), which is a known oestrogenic compound. The identification and quantification of BPA were performed by using gas chromatography coupled with mass spectrometry. It was noted that the detection method used in this study was able to achieve an average recovery ranging from 88.2 to 94.1% of BPA with standard deviations of less than 10% in different spiked samples. The detection limit of the analytical protocol was determined at 20 ng L(-1). Based on the analytical protocol, it was noted that a low level of BPA (1.18-3.04 microg L(-1)) could be detected in feed water (effluent of an activated sludge treatment system) to the dual membrane water reclamation system. The results obtained suggested that BPA could be easily chlorinated by sodium hypochlorite with a dosage of 4 to 5 mg L(-1) and a contact time of 1 to 2 min. In this lab-scale study, a satisfactory removal of BPA was readily obtained by RO and BPA was abated to an undetectable level in the product water. It was noted that the RO rejection characteristic of BPA was not sensitive to the variations in raw feed water characteristics experienced in this study. In addition, it was noted that BPA concentration present in raw feed water did not exert any significant impact on RO performance in terms of BPA rejection. The results of this study demonstrated that membrane technology could be effectively used for BPA removal.

Three reactor set-ups were investigated, namely nitrification UCBR prior to coupling, coupled UCBR-packed bed system for nitrogen removal, and de-coupled recovering UCBR. Batch studies were conducted on the biofilm particles taken from the UCBR. A mathematical model was developed to estimate the growth kinetics of the biofilm autotrophic and heterotrophic bacteria. Heterotrophs was noted to accumulate on the nitrifying biofilm due to the effect of residual COD from the packed bed column during the coupled reactor phase. The growth of heterotrophs had affected the substrate removal rates, biofilm morphology, and growth kinetics of nitrifying bacteria. For example, µm of ammonium oxidizing bacteria decreased from 0.55 to 0.19 d-1, while Ks increased from 1.42 to 3.34 mg N/L. This study demonstrated that µm and Ks of the nitrify bacteria changed with the type of substrate. Hence, growth kinetics would not be the same for nitrifying bacteria that is exposed to residual carbon in a coupled UCBR-packed bed system and a single UCBR that is fed on organic-carbon free substrate.

Bacterial growth, konjac powder utilization and β-mannanase production by Bacillus licheniformis NK-27 in batch fermentation were used to develop a model of the process. The optimal set of parameters was estimated by fitting the model to experimental data. The results predicted by the model were in good agreement with the experimental data.

A predenitrification system consisting of an ultracompact biofilm reactor (UCBR) and a packed bed column was used for removing nitrogen from synthetically simulated wastewater. The UCBR column was maintained under aerobic conditions to favor nitrification process, while the packed bed column was operated under an anoxic environment for denitrification process. A peristaltic pump was used to recycle fluid between the anoxic-packed bed and aerobic-UCBR columns to facilitate nitrogen removal. Five recycle ratios (R) were investigated, namely, 3, 4, 5, 6, and 10. The highest average total nitrogen (TN) removal rate was achieved at R=4. The NH4+-N, TN, and chemical oxygen demand (COD) removal rates at this R were 0.56±0.05kg NH4+-N/m3/day, 0.39±0.09kg TN/m3/day, and 1.83±0.18kg COD/m3/day, respectively. It was noted that poor nitrification in the UCBR was accompanied by a corresponding reduction in overall TN removal efficiency. This observation suggested that nitrification process was the limiting step for TN...

A novel coccobacilli group found previously in enhanced biological phosphorus removal (EBPR) systems was further revealed to have a high degree of diversity and distribution in various activated sludge systems. Phylogenetic analysis based on 14 existing and 18 newly retrieved 16S rRNA sequences revealed that these sequences formed a novel cohesive cluster with seven subgroups in the gamma-Proteobacteria. Fluorescence in situ hybridization with a set of probes designed specifically targeting the novel group at different hierarchical levels showed that the novel group with a coccoid (2-4 micro m) to occasionally long-rod (up to 20 micro m) shape widely distributed and in some cases predominated in sludge samples taken from nine lab- and full-scale EBPR systems (10-50% of total cells) and four conventional activated sludge systems (1-10%). Variation of predominance was also observed among those subgroups in systems showing deteriorated or effective EBPR activity.

Addition of glucose as the co-substrate and the use of a water-based polymer to enhance granulation were studied with the aim of shortening the start-up period of an anSBR (anerobic sequencing batch reactor) for high-strength industrial wastewater treatment. An initial start-up feed composition consisting of 70% sucrose and 30% industrial wastewater was favorable to reduce the start-up time. Increase in the average particle size and reduction in settled supernatant turbidity was observed with increased water-based polymer addition up to a concentration of 0.1 m/L. Polymer dosages above 0.1 ml/L were undesirable as big and “flaky” flocs were formed which prevented the flocs from settling quickly. Addition of 0.005 ml/L to 0.1 ml/L polymer to the mixed liquor had no observable adverse effects on the anaerobic biomass metabolism. Instead, the addition of the polymer appeared to improve biogas production and had an overall positive effect on anSBR performance treating the industrial wastewater.

Two packed bed column (PB) systems, namely anoxic-anoxic and anoxic-oxic were investigated for treatment of wastewater containing high concentrations of nitrogen (N) and COD. The anoxic-anoxic PB system was able to achieve N and COD removal rates of up to 6.70 kg N/m3.d and 26.02 kg COD/m3.d, respectively. The responding removal rates of the anoxic-oxic PB system were 7.41 kg N/m3 and 28.00 kg COD/m3.d, respectively. The N and COD removal efficiencies of anoxic anoxic PB system were in the range of 99.2-100% and 97.2-98.8%, respectively. The corresponding removal efficiencies of anoxic-oxic PB system were 97.5-100% and 98.6-99.4%, respectively. These findings showed that a PB system consisting of anoxic-oxic columns in series has a high capacity to remove nitrogenous and carbonaceous compounds even though the influent to the anoxic stage was oxygenated. Better system stability in terms of denitrification was, however, obtained with the anoxic-anoxic system.

Bulk salt concentration within a membrane channel could vary appreciably for different RO/NF membrane processes, and it even changes along a single membrane channel, which may have an important impact on solute transport through the membrane. However, little research has been conducted on the effects of concentration on transport behaviors. The purpose of this study was to demonstrate a valid method from fundamental theories on membrane transport for predicting the effects of feed salt concentration on salt rejection through RO/NF membranes. The salt transport characteristics under different feed salt concentrations were simulated using the Nernst-Planck-Donnan model. This numerical analysis requires the determination of three key parameters relating to membrane properties; namely, effective membrane thickness, effective membrane pore radius, and effective membrane charge density. The first two properties are independent of bulk salt concentration, whereas the third one could be related to bulk salt conce...

Performance of a two-stage full-scale reverse osmosis (RO) process for a desalination plant in Florida was simulated with a mathematical model based on the principles of membrane transport and mass conservation. In this model, water flux at any point along the filtration channel is calculated locally according to the basic transport theory of RO membranes. The changes in cross-flow velocity and salt concentration along the filtration channel were determined using mass balance principles of water and salt. Simulations of the plant performance were compared with the in-plant observation data over a period of more than 300 days. The results showed that the model could adequately describe the performance of the full-scale RO process based on a few module and operating parameters. The study also revealed that salt rejection of a RO membrane changed with feed salt concentration. The osmotic pressure coefficient that fits best with performance of this plant was substantially lower than the value determined with ...

Geogenic inorganic arsenic contamination in drinking water has been raising public health concern especially in developing countries. Cost-effective and stopgap arsenic removal method for household use (cooking and drinking) is very urgent. Several iron treated natural materials such as Fe-treated activated carbon (FeAC), Fe-treated gel beads (FeGB) and iron oxide-coated sand (IOCS), were investigated in this study for arsenic removal from dispersed household drinking water supply (scattered wells in the endemic arsenic poisoning areas). IOCS showed consistently good performance in terms of As(III) and As(V) removal in batch tests, column tests and field experiment. As(V) adsorption decreased slightly but As(III) adsorption maintained relatively stable when the pH value was increased from 5 to 9. In strong hardness water (612.5 mg/L CaCO3), As(III) adsorption efficiency was noted to decrease. The adsorption data obtained in column test fitted well to the Langmuir isotherm model. The adsorbent recovery efficiency was above 94% when using 0.2N NaOH regenerated the columns. In addition, 200 L of product water was produced by the household device (containing 3.0 kg IOCS produced) when the influent arsenic concentration ranging from 0.202 to 1.733 mg/L was encountered during the field experimental study conducted in Shanyin County, China. Neither the iron leaching nor other water quality deterioration was observed. It was noted in this study that IOCS is a promising medium for arsenic removal from household drinking water supplies.

Two laboratory-scale anaerobic sequencing batch reactors (anSBRs) were used to investigate the effectiveness of polymer addition for enhancing granulation. Mixed liquor volatile suspended solids (MLVSS) concentrations in R1 (with a polymer supplement) and R2 (control) were maintained at approximately 5 g/L. Granule development was measured by determination of the average bioparticle diameter of biosolids from the anSBRs. Addition of cationic polymer to R1 started on the 47th day after reactor start-up at a dosage of 1 ppm (on reactor volume) once per every two cycles. The cationic polymer had a beneficial effect on granulation. Compared to the control, it shortened the granulation process by approximately four months. Within the range investigated, food-to-microorganism (F/M) ratios at 0.5–0.6 g COD/g VSS d were also beneficial to granulation. After 300 days operation (at F/M ratio 0.5 g COD/g VSS d), the average bioparticle diameter of R1 was 0.78 mm, while R2 was only 0.39 mm. R1, aside from having a larger granule size, also had a higher methane production and lower soluble COD in effluent at F/M ratio 0.6 g COD/g VSS d compared to R2.

This paper investigated the variation of assimilable organic carbon (AOC) concentrations in water from several typical water treatment plants and distribution systems in a northern city of China. It is concluded from this study that: (1) The AOC in most of the product water of the studied water treatment plants and the water from the associated distribution systems could not meet the biostability criteria of 50-100 microg/L. (2) Only 4% of the measured AOC concentrations were less than 100 microg/L. However, about half of the measured AOC values were less than 200 microg/L. (3) Better source water quality resulted in lower AOC concentrations. (4) The variation of AOC concentrations in distribution systems was affected by chlorine oxidation and bacterial activity: the former resulted in an increase of AOC value while the latter led to a reduction in AOC. (5) The variation of AOC concentration followed different patterns in different distribution systems or different seasons due to their respective operational characteristics. (6) Less than 30% of AOC could be removed by a conventional treatment process, whereas 30-60% with a maximum of 50-60% could be removed by granular activated carbon (GAC). (7) The observation via scanning electron microscope (SEM) on distribution pipe tubercle samples demonstrated that the pipe inner wall was not smooth and bacteria multiplied in the crevice as well as in the interior wall of distribution pipes.

Lab-scale and pilot-scale distillation systems were assessed in this study and the effectiveness of the treatment processes on Assimilable Organic Carbon (AOC) removal was also investigated. Seawater as one of the alternative water sources was used as thefeed water and the resulting product water was intended forindustry use. Acidification, ion trapping and anti-scaling chemical dosing were adopted as the pre-treatment processes to the feed water before distillation for pilot-plant system. The AOC assay was used to evaluate the efficiencies of various unitprocesses for AOC removal. Heterotrophic Plate Counts (HPC) wasadopted in conjunction with AOC to determine the biological stability of the water samples. It is noted that the distillationsystem was able to produce a product water with an acceptable AOCconcentration of less than 20 μg acetate-C L-1. This would suggest that the distillation system was capable of delivering a biologically stable product water. The results from lab-scale system indicated that pretreatment such as acidification, chlorination and antiscalant would increase AOC, although this does not affect the general performance of distillation system.

A new engineering strain, Bacillus pumilus c172-14 (pBX 96), was obtained by introducing the pBX 96 plasmid, which carries the alpha-amylase amy gene, into the host strain of alkalophilic Bacillus pumilus c172 via transformation. The newly constructed strain was found to express the amy gene and could use starch instead of glucose or starch hydrolysate as carbon source for its fermentation of alkaline protease. The pBX 96 plasmid in the new host was found to be segregationally and structurally stable. The expression of amy gene did not affect the host strain's resistance to bacteriophages. Moreover, the level of alkaline protease was improved significantly compared with the parent strain. The constructed strain gave a maximum alkaline protease activity of 14,014 U/ml in shaking flask after 48 h cultivation when growing in a medium containing 6% corn meal, 4% soybean flour, 0.4% Na2HPO4, 0.03% KH2PO4, 0.02% MgCl2, 0.3% CaCl2, 0.25% Na2CO3, 0.1% glucose, and 20 microg/ml kanamycin (pH 7.0). The optimal pH value and temperature of the alkaline protease were 11.0 and 40 degrees C, respectively. This enzyme was stable over a pH range of 8-11. Its residual activity remained at 100% when treated under a temperature of less than 45 degrees C for 30 min. The corresponding residual activity reduced to 65% of its optimal value at 60 degrees C for 30 min. The alkaline protease was a kind of serine protease, which was demonstrated by the complete inactivation by PMSF (1 mM). This newly constructed strain will be useful in the alkaline protease industry.

A modified Assimilable Organic Carbon (AOC) procedure was adopted in conjunction with Heterotrophic Plate Count (HPC) method to assess the effect of Single Effect Distillation (SED) and Reverse Osmosis (RO) lab-scale systems on the biological stability of industrial water. Industrial water was collected from a local Industrial Water Works, pre-treated with alum coagulation and cartridge filtration, before being subjected to advanced water treatment. The results obtained in this study indicated that AOCs in the SED product water were in the range of 70-80 micrograms acetate-C/L, while those in the RO product water ranged from 30-40 micrograms acetate-C/L in the 15-min permeate to 55-65 micrograms acetate-C/L in the 3-hr permeate. The above findings suggested that product water of both systems were potentially biologically unstable and would likely lead to bacteria regrowth during its distribution and storage. Removal efficiencies of lab-scale RO and SED systems on AOC were as high as 90%, dependent on the concentration of AOC-NOX in the industrial water. The RO system had much higher organic removal efficiencies in terms of AOC and DOC than the SED system. Organics removed from both feed waters were found to be concentrated in the brine water and rejected water in SED and RO systems respectively.

Denitrifying phosphorus removal was verified in a laboratory anaerobic/anoxic Sequencing Batch Reactor (A/A SBR) for a period of 18 months. The results obtained demonstrated the ability of the anaerobic/anoxic strategy to enrich the growth of denitrifying phosphorus bacteria (DPB) capable of taking up phosphate under anoxic conditions by using nitrate as the electron acceptor. Phosphorus removal efficiency ranging from 40-100% could be attained in an A/A SBR system. Simultaneous anoxic phosphate uptake and biological denitrification under anaerobic/anoxic condition occurred in this system. Batch tests showed, however, that simultaneous presence of carbon and nitrate would be detrimental to denitrifying phosphorus removal. Results of bacteria studies suggested that three denitrifying isolates had aerobic phosphorus removing ability.

The filter media in biofiltration systems play an important role in removing potentially harmful pollutants from urban stormwater runoff. This study compares the heavy metal removal potential (Cu, Zn, Cd, Pb) of five materials (potting soil, compost, coconut coir, sludge and a commercial mix) using laboratory columns. Total/dissolved organic carbon (TOC/DOC) was also analysed because some of the test materials had high carbon content which affects heavy metal uptake/release. Potting soil and the commercial mix offered the best metal uptake when dosed with low (Cu: 44.78 μg/L, Zn: 436.4 μg/L, Cd, 1.82 μg/L, Pb: 51.32 μg/L) and high concentrations of heavy metals (Cu: 241 μg/L, Zn: 1127 μg/L, Cd: 4.57 μg/L, Pb: 90.25 μg/L). Compost and sludge also had high removal efficiencies (>90%). Heavy metal leaching from these materials was negligible. A one-month dry period between dosing experiments did not affect metal removal efficiencies. TOC concentrations from all materials increased after the dry period. Heavy metal removal was not affected by filter media depth (600 mm vs. 300 mm). Heavy metals tended to accumulate at the upper 5 cm of the filter media although potting soil showed bottom-enriched concentrations. We recommend using potting soil as the principal media mixed with compost or sludge since these materials perform well and are readily available. The use of renewable materials commonly found in Singapore supports a sustainable approach to urban water management.

Nitrification of the MBR process for sewage treatment was investigated with a pilot scale plant in this study. Complete nitrifcation occurred where the sludge retention time (SRT) was over 5 days. The maximum nitrification rate (Rmax) of the biomass was determined with batch tests and was found to be around 1.71 – 2.0 mgNO3--N/gVSS-h. Nitrification was affected more by the influent C/N ratio than SRT.

The factors influencing foam index were identified and their effects on foam index were investigated. It was noted that increasing the diameter of the flotation cell led to an increase in foam index. The maximum foam index was found to occur at a constant air/solids ratio when MLSS was varied with time of aeration or airflow. A good degree of correlation was also obtained between filament count and foam index. A small concentration of Surfactants was sufficient to induce foaming. However, further increase in surfactants showed relatively little influence on Foam Index.

This study consisted of two stages. The first stage was to cultivate denitrifying biofilm with a simplified UCBR while the second stage was to investigate the performance of a standard UCBR for nitrate removal. The volumetric nitrate-N conversion rate increased steadily from less than 0.5 kg/m3.d to about 2.5 kg/m3.d towards the end of Stage 1. Reactor instability and poor biofilm morphology had led to a relatively low nitrate-N conversion rate during stage 1 of operation. In Stage 2, the conversion rate increased rapidly to 6.5 kg/m3.d within 4 days and increased steadily to 10.5 kg/m3.d, thereafter. The biofilm formation in Stage 2 was better than that attained in Stage 1. Biofilm density and biomass concentration in the reactor were in the range of 20.5 to 29.0 g/L and 1 to 3 g/L, respectively. The specific growth rate of the denitrifiers (μ) and the observed biomass growth yield coefficient (Yobs) in the reactor varied within the ranges of 1.5-4.2 d-1 and 0.20-0.65 g biomass/g nitrate-N, respectively. The specific nitrate-N conversion rate (γ) was within the range of 1.8-3.8 g nitrate-N/g biomass.d.

This study investigated the effect of MLSS concentration in a sequencing batch membrane bioreactor on COD and nitrogen removal as well as flux. Two values of MLSS (5 g/l and 10 g/l) were investigated in this study. The strength of the feed was varied to achieve a target F/M ratio of 0.5 based on COD. Accordingly, the concentration of COD was determined as 3.5 and 7.0 g/l for the 5 and 10 g/l MLSS targets, respectively. The test results showed that an average COD removal of 98.5% was achievable. However, it was noted that nitrification inhibition occurred. Nitrification inhibition occurred because of two factors, namely high NH4+–N concentration and high DO demand. High NH4+–N in the feed led to the inhibition of nitratation and thus high nitrites are found in the effluent. High DO demand due to high feed COD concentration led to an extended period with low DO levels inside the reactor thus retarding the conversion of NH4+–N. The increase in the MLSS concentration from 5 to 10 g/l led to a decrease in the average flux from11.1 l/m2 · h to 9.6 l/m2 · h. An increase in aeration, from 2.0 to 8.0 l/min, did not lead to any significant improvement in terms of fouling.

Using a step-by-step approach, a system-specific non-mechanistic model based on statistical analyses of real-world response of process parameters to bulking, was formulated for an aerobic Sequencing Batch Reactor (SBR). The approach involved 2 phases — “Diagnosis” and “Analysis”. In “Diagnosis” phase, model parameters were identified via statistical rules and existing knowledge base on bulking, while in the “Analysis” phase, the parameters were modelled with the Sludge Volume Index (SVI) to formulate the non-mechanistic model. Validation results yielded satisfactory results for the modelling analysis. The statistical approach was executed using a multivariate data analysis package and resulted in a non-mechanistic model that was practically appealing to practitioners for its ease of use as a predictive tool for bulking. This approach, being dependent only on data analysis and statistical modelling, required no bench-scale experiments to be conducted for preliminary identification of the bulking problem. Furthermore, such an approach being algorithmic in nature, could potentially form the concept behind design of expert systems for very rapid, and economical diagnosis of bulking problems before a more in-depth and slow analytical approach involving costly laboratory procedures is adopted.

The AOC (assimilable organic carbon) method was used in this study to evaluate the biological stability of potable water. The potable water was drawn from a waterworks located in a petrochemical industrial area in China. Infrared spectra analysis was adopted in this study to examine the relationship between treatment process and organic compounds in water. By monitoring the AOC concentration in groundwater, potable water and the effluent of each treatment process (biological pre-treatment, ozonation, GAC adsorption), the following were noted: (1) a considerable AOC concentration could still be detected in potable water after advanced treatment processes, such as ozonation and activated carbon adsorption. Relatively poor biological stability was also noted in the potable water; (2) GAC was the most effective process with a total AOC removal efficiency of more than 80%. The corresponding biotreatment removal efficiency was only 45%. However, ozonation yielded a negative overall removal efficiency of −119%; (3) while biological pre-treatment and GAC adsorption contributed towards a biologically stable water, ozonation yielded oxidation products which were biologically unstable. Ozonation, if used, should therefore be combined with the GAC or biological processes. Treatment processes (like ozonation) which increased the amount of organics in carbonyl group would likely lead to poor product water biological stability.

Water produced by advanced treatment of a groundwater was evaluated to determine the amount of DBPs (Disinfection By-Products) including trihalomethanes (THMs). Both Gas Chromatography (GC) and Gas Chromatography/Mass Spectrometry (GS/MS) were adopted for detection and identification of DBPs such as trihalomethanes (THMs), halo-acetic acids (HAAs) and aldehydes. Two disinfection modes (ozonation followed by chlorination and chlorination alone) were compared to determine the DBPs generation. The mutagenitic acivity of ozonated water, chlorinated water after ozonation and potable water was assessed using the Ames test. Chloroform, dichloroacetic acid (DCAA) and trichloroacetic acid (TCAA) were the main constituents of THMs and HAAs, respectively. THMs accounted for more than 85% of all DBPs measured, whereas haloacetic acids accounted for around 14%. Ozonation followed by chlorination proved to be better in terms of THMs and HAAs control. The combined system produced 28.3% less DBPs compared to chlorination alone. Ozonation was found capable of reducing mutagenic matter in the groundwater by 54.7%. The combined system also resulted in water with no mutagenicity.

The influence of process conditions (substrate loading rate and detachment force) on the structure of biofilms grown on basalt particles in a Biofilm Airlift Sus- pension (BAS) reactor was studied. The structure of the biofilms (density, surface shape, and thickness) and mi- crobial characteristics (biomass yield) were investigated at substrate loading rates of 5, 10, 15, and 20 kg COD/ m 3 z day with basalt concentrations of 60 g/L, 150 g/L, and 250 g/L. The basalt concentration determines the number of biofilm particles in steady state, which is the main determining factor for the biofilm detachment in these systems. In total, 12 experimental runs were per- formed. A high biofilm density (up to 67 g/L) and a high biomass concentration was observed at high detach- ment forces. The higher biomass content is associated with a lower biomass substrate loading rate and there- fore with a lower biomass yield (from 0.4 down to 0.12 gbiomass/gacetate). Contrary to general beliefs, the ob- served biomass detachment decreased with increasing detachment force. In addition, smoother (fewer protuber- ances), denser and thinner compact biofilms were ob- tained when the biomass surface production rate de- creased and/or the detachment force increased. These observations confirmed a hypothesis, postulated earlier by Van Loosdrecht et al. (1995b), that the balance be- tween biofilm substrate surface loading (proportional to biomass surface production rate, when biomass yield is constant) and detachment force determines the biofilm structure. When detachment forces are relatively high only a patchy biofilm will develop, whereas at low de- tachment forces, the biofilm becomes highly heteroge- neous with many pores and protuberances. With the right balance, smooth, dense and stable biofilms can be obtained. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 58: 400-407, 1998.

This study aimed to provide the first and comprehensive data on the occurrence of 17 target pharmaceuticals and personal care products (PPCPs) in urban water environment in Singapore. Meanwhile, this study also verified the suitability of these PPCPs as specific markers of raw wastewater contamination in receiving water bodies in highly urbanized areas where both surface water and groundwater are not impacted by the discharge of treated wastewater effluents. Analytical results of wastewater showed that among 17 target PPCPs examined, only 5 PPCPs were detected in 100 % of raw wastewater samples, including acetaminophen (ACT), carbamazepine (CBZ), caffeine (CF), diethyltoluamide (DEET), and salicylic acid (SA). Similarly, these PPCPs were found in most surface water and groundwater. Interestingly, the three PPCPs (ACT, CBZ, and SA) were only detected in surface water and groundwater in the sampling sites close to relatively older sewer systems, while they were absent in background samples that were collected from the catchment with no known wastewater sources. This suggests that ACT, CBZ, and SA can be used as specific molecular markers of raw wastewater in surface water and groundwater. This study also confirmed that CF and DEET were not really associated with wastewater sources, thus cannot serve well as specific molecular markers of wastewater contamination in receiving water bodies. To the best knowledge of the authors, the use of ACT and SA as specific molecular markers of raw wastewater contamination in urban surface waters and groundwater was first reported. Further studies on the use of ACT, CBZ, and SA along with other chemical/microbial markers are recommended to identify and differentiate contamination sources of surface waters/groundwater.

There is no quantitative data on the occurrence of artificial sweeteners in the aquatic environment in Southeast Asian countries, particularly no information on their suitability as indicators of raw wastewater contamination on surface water and groundwater. This study provided the first quantitative information on the occurrence of artificial sweeteners in raw wastewater, surface water and groundwater in the urban catchment area in Singapore. Acesulfame, cyclamate, saccharin, and sucralose were ubiquitous in raw wastewater samples at concentrations in the range of ng/L–μg/L, while other sweeteners were not found or found only in a few of the raw wastewater samples. Residential and commercial effluents were demonstrated to be the two main sources of artificial sweeteners entering the municipal sewer systems. Relatively higher concentrations of the detected sweeteners were frequently found in surface waters at the sampling sites located in the residential/commercial areas. No significant difference in the concentrations of the detected sweeteners in surface water or groundwater was noted between wet and dry weather conditions (unpaired T-test, p> 0.05). Relatively higher concentrations and detection frequencies of acesulfame, cyclamate and saccharin in surface water samples were observed at the potentially impacted sampling sites, while these sweeteners were absent in most of the background surface water samples. Similarly, acesulfame, cyclamate, and saccharin were found in most groundwater samples at the monitoring well (GW6), which is located close to known leaking sewer segment; whereas these were absent in the background monitoring well, which is located in the catchment with no known wastewater sources. Taken together, the results suggest that acesulfame, cyclamate, and saccharin can be used as potential indicators of raw wastewater contamination in surface water and groundwater.

A high-throughput method for the simultaneous determination of 24 pharmaceuticals and personal care products (PPCPs), endocrine disrupting chemicals (EDCs) and artificial sweeteners (ASs) was developed. The method was based on a single-step solid phase extraction (SPE) coupled with high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) and isotope dilution. In this study, a single-step SPE procedure was optimized for simultaneous extraction of all target analytes. Good recoveries (≥ 70%) were observed for all target analytes when extraction was performed using Chromabond(®) HR-X (500 mg, 6 mL) cartridges under acidic condition (pH 2). HPLC-MS/MS parameters were optimized for the simultaneous analysis of 24 PPCPs, EDCs and ASs in a single injection. Quantification was performed by using 13 isotopically labeled internal standards (ILIS), which allows correcting efficiently the loss of the analytes during SPE procedure, matrix effects during HPLC-MS/MS and fluctuation in MS/MS signal intensity due to instrument. Method quantification limit (MQL) for most of the target analytes was below 10 ng/L in all water samples. The method was successfully applied for the simultaneous determination of PPCPs, EDCs and ASs in raw wastewater, surface water and groundwater samples collected in a local catchment area in Singapore. In conclusion, the developed method provided a valuable tool for investigating the occurrence, behavior, transport, and the fate of PPCPs, EDCs and ASs in the aquatic environment.

A bench-scale fluidised bed bioreactor was used to treat aquaculture effluent intended for recycling. The reactor was loaded with ammonia-nitrogen (NH 4 -N) from 0.025 to 5.675 g m −2 day −1 . Maximum NH 4 -N removal was 82% of influent concentration when loading was between 0.201 and 0.397 g m −2 day −1 ; at this level, effluent NH 4 -N did not exceed 0.05 mg 1 −1 .

The synthesis, spectroscopic and structural characterization of the stable gallium hydride compound [Ga(TPP)H] (TPP=5,10,15,20-tetraphenylporphyrinato) have been reported. The hydride compound was synthesized in high yield (85%) by reducing [Ga(TPP)Cl] with sodium borohydride in N , N -dimethylformamide. The title compound was fully characterized by spectroscopic methods (IR, UV–Vis, and 1 H NMR spectroscopy) and its molecular structure was established by X-ray crystallography. The Ga–H IR stretch occurs at 1864 cm −1 , and the hydride 1 H NMR resonance locates at −6.47 ppm. The gallium–hydrogen distance is 1.48(4) A, whereas the gallium atom lies 0.46(1) A from the perfect porphyrin plane.

Three submerged anaerobic membrane bioreactors (SAnMBR) with solids retention times (SRTs) of 30, 60 and 90d were set up for domestic wastewater treatment. Total COD removal rates higher than 83% were achieved. Maximum biogas production was 0.5L CH4d(-1) (0.010L CH4 (gMLVSS)(-1)d(-1); MLVSS: mixed liquor volatile suspended solids) at a SRT of 90d. A longer SRT benefited biomass accumulation and biogas production due to enhanced dominancy of methanogens. With the SRT increasing from 30 to 90d, enhancement of hydrolysis from 35 to 56% was identified as the major reason for the better efficient acidification and methanogenesis observed. Best treatment performance and membrane fouling control were observed for the SAnMBR operated at a SRT of 60d. Soluble microbial products or specific soluble microbial products that accumulated with SRT decrease from 60 to 30d led to a faster membrane fouling. With an increase of SRT from 60 to 90d, higher mixed liquor suspended solids concentration caused more particle deposition on the membrane surface, while more soluble microbial products or specific soluble microbial products was attributed to more metabolism products generation.

The performance of an ultra-compact biofilm reactor (UCBR) treating domestic wastewater (DWW) collected from a local water reclamation plant; and gradually shifting to a mono-type carbon source synthetic wastewater (SWW) combined with DDW (CWW) and finally SWW; was investigated in this study. The total COD concentrations of influent DWW and CWW/SWW were 413.6 ± 80.8 mg/L and 454.9 ± 51.3 mg/L, respectively. The UCBR was able to achieve average total COD removal efficiencies of 70 ± 10% and 80 ± 4% for DWW and SWW respectively. The total COD concentrations of the effluent of DWW and CWW/SWW were 122.5 ± 44.4 mg/L and 89.7 ± 10.3 mg/L, respectively. These observations suggested that heterotrophs in the UCBR system were able to better assimilate and remove carbon of mono-type SWW compared to diverse carbon sources such as DWW; although the influent soluble COD concentrations of the SWW were higher than those of the DWW. However, the effluent NH4+-N concentrations for both types of wastewater were rather similar

An experimental prawn pond of 600 sq m surface area and 2 m depth was used for the cultivation of tiger prawn. Thirty-thousand 14-day PL flies were stocked. Water treatment systems consisting of primary sedimentation, aerated biofilter and inclined plate final sedimentation were installed for treatment and recycling of the pond water. With complete recycling and reuse of the pond water and occasional replenishing with seawater to make up for losses due to evaporation, water quality was maintained at an acceptable level. Survival rate of the prawn was above 80 %. Prawn yield was estimated to be around 7.6 tonnes/hectare-cycle or 22.8 tonnes/hectare-year.

Change in light output of Photobacterium phosphoreum was used as a screening test for detecting the level of toxicity in clarified sewage, SBR-treated effluent, and mixed liquors. Besides using the 2% and 90% Microtox screening test protocols, a 45% screening test procedure was developed. Previously reported studies on SBR removal of BOD, COD, TSS and selected microorganisms have shown that effective and stable removal of these would generally require two or more hours of REACT. This would also result in good effluent quality in terms of toxicity. The removal of toxicants appeared to be due to their adsorption onto the biomass during FILL followed by their conversion to less- or non-toxic products and/or the assimilation and accumulation of such toxicants in the sludge. Some desorption of toxicants was observed during SETTLE. Efficient removal of toxicity, in excess of 90%, may be achieved with a REACT of 1·5 h or more.

A method based on denaturing gradient gel electrophoresis (DGGE) banding polymorphism was developed for rapid small-subunit (SSU) rDNA clone screening and microbial diversity estimation. Clones with correct rDNA insertion were initially identified using whole-cell PCR with vector-specific primers. Subsequently, the correct PCR products were re-amplified with nested primers in a DGGE analysis. An average of five to 10 individual DGGE-PCR products could be mixed together and loaded into a DGGE well, and at least 125 to 250 clones could be screened and compared within one DGGE gel. This approach eliminated the reproducibility problem associated with DGGE, increased the ability to screen a large set of clones at a relatively affordable cost, and was shown to be more sensitive than the restriction fragment length polymorphism method in identifying 10 different but phylogenetically closely related 16S rDNA fragments from 126 clones obtained from an anaerobic sludge sample.

The relationships between the loading factor (Li) and BOD5, COD, TSS, total coliform, fecal coliform and coliphage removals were explored using three laboratory SBRs receiving a medium-to-low strength domestic sewage. The SBRs were operated with different FILL/REACT ratios in a 6-h cycle. Not unexpectedly results showed that increases in Li led to decreases in the removals of BOD5, COD, TSS and potential pathogen indicators. However, low SVIs (Sludge Volume Index) in the SBR need not necessarily mean good solids settleability. Good settleability is, however, necessary for good TSS removal as it led to better removals of total BOD5, total COD and indicators of potential pathogens. During FILL, fermentation reactions probably occurred and this resulted in up to 86% reduction of the initial dissolved BOD5 concentration. Degradation of waste then continued into the REACT period. This preliminary assessment showed that the SBR is, potentially, a viable option for domestic wastewater treatment, especially since the aeration time required for treatment to achieve comparable effluent quality is shorter than the conventional continuous activated sludge systems which are usually operated with about 3–8 h of aeration time.

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

The rational design of closed aquaculture systems requires data on metabolite production rates. The metabolite of primary concern is often ammonia. Ammonia formation rates for a number of tropical ornamental fish types and sizes were determined. Cyprinus carpio, Barbus conchonius, Pseudotropheus auratus and Carassius auratus auratus were used as representative egg-layers while Xiphophorus variatus and Xiphophorus helleri represented the live-bearers. Specific metabolite production rates, R′, were determined not only in terms of mass of fish but also the amount of feed. For instance, R′ (Amm-N) for 1.33 g unit size Barbus conchonius was determined to be 155.9 mg Amm-N kg-fish−1% feed−1 day−1. In an attempt to produce a general model for all the ornamental fish investigated, all values of R′ obtained were correlated with fish sizes to produce an equation R′ (Amm-N) = 1.57-[30×log(itUW)] where UW = unit fish size.

Rain water was collected from storm drains and after filtration was stored at an earth pond. The pond water was the main source of fresh water supply for intensive fish cultivation. To conserve the limited water resources, effluent from fish cultivating ponds was treated and recycled for reuse. With proper blending of water from the storing earth pond and recycling of the water between the fish ponds and the fish lagoon, water quality at the fish ponds and the lagoon was maintained at acceptable levels. Although fresh water replenishing rate was low there was no serious buildup of metals and total solids in the fish ponds.