Removals of pharmaceutical compounds from hospital wastewater in membrane bioreactor operated under short hydraulic retention time.

Pilot-scale membrane bioreactor (MBR) was operated at a short hydraulic retention time (HRT) of 3 h for the treatment of hospital wastewater. The removals of eleven pharmaceutical compounds in MBR operated at different mixed liquor suspended solids (MLSS) level were investigated during which nitrification degree was differed. The results experiments revealed the importance of immediate adsorption onto the colloidal particles in supernatant of MBR sludge and subsequently removed by membrane filtration for the recalcitrant pharmaceutical compounds. Nevertheless, the removals through biodegradation during short HRT were also found significant for some compounds. DGGE profile revealed the development of pharmaceutical degrading microorganisms in MBR.

Organic carbon recovery and photosynthetic bacteria population in an anaerobic membrane photo-bioreactor treating food processing wastewater.

Purple non-sulfur bacteria (PNSB) were cultivated by food industry wastewater in the anaerobic membrane photo-bioreactor. Organic removal and biomass production and characteristics were accomplished via an explicit examination of the long term performance of the photo-bioreactor fed with real wastewater. With the support of infra-red light transmitting filter, PNSB could survive and maintain in the system even under the continual fluctuations of influent wastewater characteristics. The average BOD and COD removal efficiencies were found at the moderate range of 51% and 58%, respectively. Observed photosynthetic biomass yield was 0.6g dried solid/g BOD with crude protein content of 0.41 g/g dried solid. Denaturing gradient gel electrophoretic analysis (DGGE) and 16S rDNA sequencing revealed the presence of Rhodopseudomonas palustris and significant changes in the photosynthetic bacterial community within the system.

Removal of organic micro-pollutants from solid waste landfill leachate in membrane bioreactor operated without excess sludge discharge.

Two-stage membrane bioreactor (MBR) system was applied to the treatment of landfill leachate from a solid waste disposal site in Thailand. The first stage anoxic reactor was equipped with an inclined tube module for sludge separation. It was followed by an aerobic stage with a hollow fiber membrane module for solid liquid separation. Mixed liquor sludge from the aerobic reactor was re-circulated back to anoxic reactor in order to maintain constant mixed liquor suspended solids (MLSS) concentration in the aerobic reactor. The removal of micro-pollutants from landfill leachate along the treatment period of 300 days was monitored. The results indicated that two-stage MBRs could remove biochemical oxygen demand (BOD), chemical oxygen demand (COD) and NH(4)(+) by 97, 87 and 91% at steady operating condition. Meanwhile organic micro-pollutant removals were 50-76%. The removal efficiencies varied according to the hydrophobic characteristic of compounds but they were improved during long-term MBR operation without sludge discharge.

Photosynthetic bacteria production from food processing wastewater in sequencing batch and membrane photo-bioreactors.

Application of photosynthetic process could be highly efficient and surpass anaerobic treatment in releasing less greenhouse gas and odor while the biomass produced can be utilized. The combination of photosynthetic process with membrane separation is possibly effective for water reclamation and biomass production. In this study, cultivation of mixed culture photosynthetic bacteria from food processing wastewater was investigated in a sequencing batch reactor (SBR) and a membrane bioreactor (MBR) supplied with infrared light. Both photo-bioreactors were operated at a hydraulic retention time (HRT) of 10 days. Higher MLSS concentration achieved in the MBR through complete retention of biomass resulted in a slightly improved performance. When the system was operated with MLSS controlled by occasional sludge withdrawal, total biomass production of MBR and SBR photo-bioreactor was almost equal. However, 64.5% of total biomass production was washed out with the effluent in SBR system. Consequently, the higher biomass could be recovered for utilization in MBR.

Removal of pollutants and reduction of bio-toxicity in a full scale chemical coagulation and reverse osmosis leachate treatment system.

Removals of pollutants and toxic organic compounds and reduction in bio-toxicity of leachate along an operating full-scale leachate treatment system utilizing chemical coagulation, sand filtration, microfiltration (MF) and reverse osmosis (RO) membrane were evaluated. High pollutant removals were achieved mainly by coagulation and sand filtration. Major toxic organic pollutants, i.e. DEHP, DBP and bisphenol A were removed by 100%, 99.6% and 98.0%. Acute toxicity test using water flea, Nile Tilapia and common carp and genotoxicity (Comet assay) were conducted to determine toxicity reduction in leachate along the treatment. Ammonia was found to be the main acute toxic compounds in leachate as determined by LC(50) but the effect of organic substances was also observed. DNA damage in fish exposed to diluted raw leachate (10% of LC(50)) was found to be 8.9-24.3% and it was subsequently decreased along the treatment. Correlation between pollutants and its bio-toxicity was established using multivariable analyses.

Treatment performance and microbial characteristics in two-stage membrane bioreactor applied to partially stabilized leachate.

A two-stage membrane bioreactor system was applied to the treatment of partially stabilized leachate from solid waste landfill in Thailand. In the system, an anoxic tank with incline tube for biomass separation from re-circulated sludge is followed by a second-stage aerobic tank in which a direct submerged hollow-fiber membrane module is used for solid-liquid separation. During steady operation of 200 days, BOD, COD, NH3 and TKN removals were found to be 99.6, 68, 89 and 86% respectively. Determination of nitrogen transforming bacteria by fluorescent in-situ hybridization technique revealed a slightly higher percentage of nitrifying bacteria in the aerobic tank and a higher percentage of denitrifying bacteria in the anoxic tank respectively. Anammox-like bacteria were also detected at relatively high percentage.

Leachate treatment and greenhouse gas emission in subsurface horizontal flow constructed wetland.

Organic and nitrogen removal efficiencies in subsurface horizontal flow wetland system (HSF) with cattail (Typha augustifolia) treating young and partially stabilized solid waste leachate were investigated. Hydraulic loading rate (HLR) in the system was varied at 0.01, 0.028 and 0.056 m(3)/m(2) d which is equivalent to hydraulic retention time (HRT) of 28, 10 and 5 d. Average BOD removals in the system were 98% and 71% when applied to young and partially stabilized leachate at HLR of 0.01 m(3)/m(2) d. In term of total kjeldahl nitrogen, average removal efficiencies were 43% and 46%. High nitrogen in the stabilized leachate adversely affected the treatment performance and vegetation in the system. Nitrogen transforming bacteria were found varied along the treatment pathway. Methane emission rate was found to be highest at the inlet zone during young leachate treatment at 79-712 mg/m(2) d whereas CO2 emission ranged from 26-3266 mg/m(2) d. The emission of N2O was not detected.

Solid waste characteristics and their relationship to gas production in tropical landfill.

Solid waste characteristics and landfill gas emission rate in tropical landfill was investigated in this study. The experiment was conducted at a pilot landfill cell in Thailand where fresh and two-year-old wastes in the cell were characterized at various depths of 1.5, 3, 4.5 and 6 m. Incoming solid wastes to the landfill were mainly composed of plastic and foam (24.05%). Other major components were food wastes (16.8%) and paper (13.3%). The determination of material components in disposed wastes has shown that the major identifiable components in the wastes were plastic and foam which are resistant to biodegradation. The density of solid waste increased along the depth of the landfill from 240 kg m(-3) at the top to 1,260 kg m(-3) at the bottom. Reduction of volatile solids content in waste samples along the depth of landfill suggests that biodegradation of solid waste has taken place to a greater extent at the bottom of the landfill. Gas production rates obtained from anaerobic batch experiment were in agreement with field measurements showing that the rates increased along the depth of the landfill cell. They were found in range between 0.05 and 0.89 l kg(-1) volatile solids day(-1). Average emission rate of methane through the final cover soil layer was estimated as 23.95 g(-2)day(-1) and 1.17 g(-2)day(-1) during the dry and rainy seasons, respectively.

Particle and microorganism removal in floating plastic media coupled with microfiltration membrane for surface water treatment.

Floating plastic media followed by hollow fiber microfiltration membrane was applied for surface water treatment. The performance of the system in terms of particle and microorganisms was investigated. The floating filter was examined at different filtration rates of 5, 10 and 15 m3/m2 x h. Treated water was then fed into a microfiltration unit where different filtration rates were examined at 0.6, 1.0 and 1.4 m3/m2 x d. It was found that polyaluminum chloride was the best coagulant for the removal of particle, algae and coliform bacteria. Average turbidity in treated water from the floating plastic media filter was 3.3, 12.2 and 15.5 NTU for raw water of 80 NTU and 12.9, 11.7 and 31.2 NTU for raw water of 160 NTU after 6 hours at the filtration rates of 5, 10 and 15 m3/m2 x h, respectively. The microfiltration unit could further reduce the turbidity to 0.2-0.5 NTU with low transmembrane pressure development of 0.3-3.7 kPa. Microfiltration membrane could retain most of algae and coliform bacteria remaining in the effluent from the pretreatment unit. It was found that at higher turbidity, algae and coliform bacteria removal efficiencies were achieved at lower filtration rate of the system of 5 m3/m2 x h whereas a higher filtration rate of 15 m3/m2 x h yielded better coliphage removal.

Methanotrophic production of extracellular polysaccharide in landfill cover soils.

A bench-scale soil reactor was used to study methane oxidation and EPS production under tropical conditions. The study of pertinent environmental factors affecting EPS production was carried out by batch cultivation of methanotrophs. These factors included variations in temperature (20 degrees C to 45 degrees C), soil water content (5% to 33%), and the supply ratios of methane/oxygen. The bench-scale study revealed that excessive EPS was accumulating in an active methane oxidation zone located 5-45 cm below the soil surface of the reactor. The observed peak rates of oxidation could not be sustained over an extended period of time due to EPS accumulation. Results from the batch cultivation experiments confirmed the production of EPS in soils subject to methane oxidation. EPS production was found to correlate with methane oxidation rates which, in turn, were regulated by the variance of temperature and soil water content. A larger amount of EPS production was obtained at 30 degrees C and 17% soil water content. Oxygen is required for methane oxidation; however, at high oxygen tension it may accelerate the production of EPS by methanotrophs causing limited oxygen diffusion and declining rates of methane oxidation.