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There has been increasing research focus on the detection and occurrence of wastewater contamination in aquatic environment. Wastewater treatment plants receive effluents containing various chemical pollutants. These chemicals may not be fully removed during treatment and could potentially enter the receiving water bodies. Detection of these chemical pollutants and source identification could be a challenging research task due to the diversified chemical and functional groups, concentration levels and fate and transportation mechanisms of these pollutants in the environment. Chemical markers such as pharmaceuticals and personal care products, artificial sweeteners, fluorescent whitening agents, sterols and stanols, and nitrate and nitrogen isotopics have been widely used by most research as markers. These markers served as indicators of wastewater contamination to the receiving bodies due to their frequent usage, resistance to biodegradability and, more importantly, anthropogenic origin. These markers are commonly used in combination to identify the contaminant source of different origins. This article discusses the main chemical markers that are used to identify wastewater contamination in receiving bodies, the current trends, and approach to select suitable chemical markers. [ABSTRACT FROM AUTHOR]

In the present study, the sorption and biodegradation characteristics of five pharmaceutical and personal care products (PPCPs), including acetaminophen (ACT), carbamazepine (CBZ), crotamiton (CTMT), diethyltoluamide (DEET) and salicylic acid (SA), were studied in laboratory-batch experiments. Sorption kinetics experimental data showed that sorption systems under this study were more appropriately described by the pseudo second-order kinetics with a correlation coefficient (R2)> 0.98. Sorption equilibrium data of almost all target compounds onto soil could be better described by the Freundlich sorption isotherm model. The adsorption results showed higher soil affinity for SA, following by ACT. Results also indicated a slight effect of pH on PPCP adsorption with lower pH causing lower adsorption of compounds onto the soil except for SA at pH 12. Moreover, adsorption of PPCPs onto the soil was influenced by natural organic matter (NOM) since the higher amount of NOM caused lower adsorption to the soil. Biodegradation studies of selected PPCPs by indigenous microbial community present in soil appeared that the removal rates of ACT, SA and DEET increased with time while no effect had been observed for the rest. This study suggests that the CBZ and CTMT can be considered as suitable chemical sewage indicators based on their low sorption affinity and high resistance to biodegradation. [ABSTRACT FROM AUTHOR]

Aluminum-based water treatment residue (Al-WTR) generated during the drinking water treatment process is a readily available recycled material with high phosphorus (P) adsorption capacity. The P adsorption capacity of Al-WTR generated from Singapore's water treatment plant was evaluated with reference to particle size range, adsorption pH and temperature. Column tests, with WTR amendments in sand with and without compost, were used to simulate the bioretention systems. The adsorption rate decreased with increasing WTR sizes. Highest P adsorption capacity, 15.57 mg PO43--P/g WTR, was achieved using fine WTR particles (>50% particles at less than 0.30 mm). At pH 4, the contact time required to reduce effluent P concentration to below the detectable range was half compared with pH 7 and 9. The adsorption rate observed at 40 ± 2 °C was 21% higher compared with that at 30 ± 2 °C. Soil mixes amended with 10% WTR and compost were able to maintain consistently high (90%) total phosphorus (TP) removal efficiency at a TP load up to 6.45 g/m3. In contrast, TP removal efficiencies associated with columns without WTR amendment decreased to less than 45% as the TP load increased beyond 4.5 g/m3. The results showed that WTR application is beneficial for enhanced TP removal in bioretention systems. [ABSTRACT FROM AUTHOR]

Microalgae in three submerged ceramic membrane photobioreactors (SCMPBRs) with different hydraulic retention times (HRTs) were fed with permeate of a submerged ceramic membrane bioreactor for a period of 3 months to investigate the lipid content and also the biodiesel quality produced at different HRTs. The lipid content, lipid productivity and fatty acid compositions for all three SCMPBRs were not significantly different at the 95% confidence level. These results suggested that insignificant change in the amount of fatty acids was observed at different HRTs that supplied varying concentration of nitrate in the medium. Among the fatty acids, palmitic acid, palmitoleic acid, oleic acid and linoleic acid were the main components, whereas stearic acid was a minor fatty acid. Since there was insignificant effect of HRT on lipid content, lipid productivity and fatty acid compositions, the optimum HRT for SCMPBRs can then be designed based on optimum nutrient removal performance and low membrane fouling propensity. [ABSTRACT FROM AUTHOR]

The article presents research on the determination of organic carbon content feasibility derived from vermicompost and empty bed contact time (EBCT) on total nitrogen (TN) removal in saturated zone. The study demonstrates the significance of the organic carbon source amount and EBCT as design criteria for the removal of optimum nitrogen. It notes that more labile carbon sources help support better rates for NT removal.

Boron removal is a challenging task for any seawater desalination plant employing a singlepass reverse osmosis (RO) system. With a pKa value of 9.25, more than 99% boron removal is normally achieved at pH >10.5. As pKa value is theoretically lower at higher salinity, an increase of borate ion and a corresponding increase in boron removal could be expected as salinity increases. However, boron removals by CPA2 and SWC4+membranes were found to decrease or, sometimes, unchanged at higher salinity where membrane zeta potentials shifted from negative values to positive values were observed at higher salinity at both pH 7 and 9. The decrease in boron removal by CPA2 membrane with increasing salinity at pH 9 could be attributed to the reduced charge repulsion mechanism. Similarly, boron removal by SWC4+ membrane decreased with increasing salinity. However, the removal efficiency reached its lowest value at 2000 mg/l of NaCl at pH 9. The subsequent increase in boron removal efficiency at salinity higher than 2000 mg/l could be attributed to size exclusion mechanism. At pH 7, the trend of boron removal by CPA2 membrane was similar to that observed at pH 9. However, the corresponding trend of SWC4+ membrane at pH 7 was different from that observed at pH 9. With a negligible amount of borate at pH 7, reduced boron removal by CPA2 membrane observed at higher salinity might be attributed to enhanced diffusion. In contrast, the relatively stable boron removal at pH 7 by SWC4+ membrane observed at all salinities suggested that size exclusion could be the dominant mechanism. [ABSTRACT FROM AUTHOR]

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, <3.0 mg/L; although the influent NH4+ -N concentrations of the DWW were 1.5 times those of the SWW. [ABSTRACT FROM AUTHOR]

The generation of brine solutions from dense membrane (reverse osmosis, RO or nanofiltration, NF) water reclamation systems has been increasing worldwide, and the lack of cost effective disposal options is becoming a critical water resources management issue. In Singapore, NEWater is the product of a multiple barrier water reclamation process from secondary treated domestic effluent using MF/UF-RO and UV technologies. The RO brine (concentrates) accounts for more than 20% of the total flow treated. To increase the water recovery and treat the RO brine, a CDI based process with BAC as pretreatment was tested. The results show that ion concentrations in CDI product were low except SiO2 when compared with RO feed water. CDI product was passed through a RO and the RO permeate was of better quality including low SiO2 as compared to NEWater quality. It could be beneficial to use a dedicated RO operated at optimum conditions with better performance to recover the water. BAC was able to achieve 15-27% TOC removal of RO brine. CDI had been tested at a water recovery ranging from 71.6 to 92.3%. CDI based RO brine treatment could improve overall water recovery of NEWater production over 90%. It was found that calcium phosphate scaling and organic fouling was the major cause of CDI pressure increase. Ozone disinfection and sodium bisulfite dosing were able to reduce CDI fouling rate. For sustainable operation of CDI organic fouling control and effective organic fouling cleaning should be further studied. [ABSTRACT FROM AUTHOR]

Drinking water biofilm development is affected by the available nutrient levels and the presence of disinfectants. Phosphorus is recognized as another important limiting nutrient besides organic carbon. In this study, drinking water biofilms were developed in annular reactors to examine the effects of phosphorus on the biofilm disinfections with free chlorine and monochloramine. Phosphorus addition was found to increase the biofilm cell number but decrease the exopolysaccharides (EPS) production. The disinfection efficacies of both free chlorine and monochloramine were increased when phosphorus was added into the reactor systems. At the same disinfection dosages, monochloramine showed greater biofilm removal efficiency than free chlorine. Monochloramine could be a better choice than free chlorine in biofilm disinfection when phosphate-based corrosion inhibitors are applied. [ABSTRACT FROM AUTHOR]

The membrane bioreactor (MBR), a combination of activated sludge process and the membrane separation system, has been widely used in wastewater treatment. However, 90% of MBR reported were employing polymeric membranes. The usage of ceramic membranes in MBR is quite rare. Four submerged ceramic membrane bioreactors (SCMBRs) with different membrane pore size were used in this study to treat sewage. The results showed that the desirable carbonaceous removal of 95% and ammonia nitrogen removal of 98% were obtained for all the SCMBRs. It was also showed that the ceramic membranes were able to reject some portions of the protein and carbohydrate, whereby the carbohydrate rejection rate was much higher than that of protein. Membrane pore size did not significantly affect the COD and TOC removal efficiencies, the composition of EPS and SMP or the membrane rejection rate, although slight differences were observed. The SCMBR with the biggest membrane pore size fouled fastest, and membrane pore size was a main contributor for the different fouling potential observed. [ABSTRACT FROM AUTHOR]

The application of immunofluorescent labeling using quantum dots for detection of inactivated Crypt osporidium parvum oocysts in spiked water samples (reservoir water, treated wastewater effluent, permeate of a membrane bioreactor, and tap water) provided more consistent results compared with the organic fluorophores label. The varying degree of particles present in the different water samples (with turbidity ranging from 0.2 to 6.1 NTU) in nonconcentrated water samples had insignificant interference on the labeled counts (2-sample t-tests, p > 0.236) using the quantum dot label, while the quantum dot label provided an advantage of approximately 50% lower interference in concentrated water samples compared with the organic fluorophores label. [ABSTRACT FROM AUTHOR]

The effects of formaldehyde on biofilm morphology and biomass activity were investigated in an ultracompact biofilm reactor (UCBR) for carbonaceous wastewater treatment. The wastewater contained a fixed amount of glucose (with a chemical oxygen demand concentration of 600 mg/L) and an increasing concentration of formaldehyde (ranging from 21.4 to 271.1 mg/L). An influent formaldehyde concentration higher than 75 mg/L could facilitate filamentous growth (on biofilm) control and lead to a higher biofilm density, which is desirable as it enhanced the UCBR performance stability. However, at an influent formaldehyde concentration higher than 214.4 mg/L, biomass production was inhibited and deteriorations of biofilm morphology and biomass activity were observed. This study showed that it was desirable to maintain an influent formaldehyde concentration lower than 202.2 mg/L, as this concentration could achieve a good biofilm morphology while not inhibiting its microbial activity. [ABSTRACT FROM AUTHOR]

Columnar packed-bed (PB) reactors with a specific surface area of 127 m²/m³ were investigated in this study for treating nitrate wastewater. This study demonstrated that a single-stage packed bed was able to achieve total nitrogen (TN) and chemical oxygen demand (COD) removal efficiencies higher than 83 and 75%, respectively. The highest achievable TN and COD removal rates were 47.2 g N/m²⋅d and 158.0 g COD/m²⋅d, respectively. The substrate removal rate in the PB column was found to follow half-order reaction kinetics, with a reaction coefficient, k, of 53.62 (mg/L)½/d. A dual-stage PB system was capable of achieving TN and COD removal efficiencies greater than 99 and 98%, respectively. Effluent TN and COD concentrations less than 6.5 mg NO3--N/L and 50.0 mg COD/L, respectively, were obtained when the dual PB system was used. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The author reflects on the urgent need to study emerging contaminants to safeguard consumers. The author asserts that the need is particularly significant for drinking water treatment and water reclamation. The author expresses that the potential treatment techniques include membrane retention, adsorption and advance oxidation.

The article discusses the use of membrane technology in removing water contaminants during reclamation. It notes that the types of membrane processes are microfiltration, ultrafiltration, nanofiltration, reverse osmosis (RO) and membrane bioreactor (MBR). It states that the use of MBR showed effective scouring and a low membrane-fouling rate. It stresses that RO has been commonly used in water reclamation and desalination due to its high-productivity and low-cost antifouling polyamide thin-film composite membranes.

The article discusses the opportunities and challenges in membrane technology for environmental applications. To resolve the issues of water shortage and water quality and achieve sustainable growth, it is widely recognized that membrane processes will increasingly play an important role and emerge as the dominant technology for water purification in the future.