The enrichment of lakes, inland seas, groundwater and rivers by nutrients such as nitrogen and phosphorus compounds, and their consequences is one of the most severe problems across the world. Transfer of nutrients from different sources into the environment causes eutrophication of surface waters, nitrate accumulation in groundwater, and others. Domestic wastewater is an important nitrogenous and phosphorous source. Among the treatment technologies for it, constructed wetland is emerging as a promising low-cost approach to improve treatment of point and diffuse sources in broad rural areas in developing countries. In this paper, the performance of two typical types of constructed wetlands, FWS (Free Water Surface) and SF (Subsurface Flow) constructed wetlands was investigated on pollutants removal, furthermore, the risk of resulting water bloom for the effluent is also discussed using the parameter of algae growth potential (AGP). The results indicated that the pollutant removal rate measured in the wetland indicated obvious seasonal change. But subsurface constructed wetland indicated more preferable pollutants removal performance and higher stability for wastewater treatment than FWS constructed wetland. The results also indicated that SF constructed wetland could alleviate the effluent's potential of resulting in eutrophication.
After growing mass and monoxenic cultures of three species of small metazoa, Nais sp., Aeolosoma hemprichi and Philodina sp. using sterilized activated sludge as the metazoan food, the effect of six kinds of metals on the specific growth rate of each metazoa was examined. EC50 (effective concentration) was used to define the metal concentration required to reduce the specific growth rate of metazoa to half of that of a control. The EC50 for A. hemprichi, Nais sp., and Philodina sp. were: 0.9, 1.3 and 5.4 mg · l-1, respectively for copper, 0.04, 0.03 and 1.4 mg · l-1 for hexavalent chromium, 3.4, 4.3 and 9.2 mg · l-1 for zinc, 14.0, 7.6 and 33.0 mg · l-1 for manganese and more than 102.4 mg · l-1 under pH adjusted (A. hemprichi and Nais sp.) for alminium and iron. It was noted that concentrations of these metals from the influent of domestic sewage treatment plants were apparently less than values of EC50 mentioned above.
A swim-bed attached-growth bioreactor (BF reactor) using a novel acryl-fiber biomass carrier (Biofringe: BF) for treating Hanoi groundwater, which is polluted by high levels of ammonium, has been developed. The swim-bed technology is aerobic and combines the advantages of fix-bed attached-growth processes, which can retain high amounts of slowly growing nitrifiers, and moving-bed attached-growth processes, which avoid clogging problems. Experiments were conducted in 7.7-l reactors, using synthetic Hanoi groundwater, containing 30 mg-N/l of ammonium. Two reactors (BF1 and BF2) were used to investigate the ammonium removal capacities; BF1 was fed influent containing 5 mg/l of iron and BF2 was fed influent without iron. Maximum ammonium removal rates of 0.24 and 0.48 kg-N/m3/d, corresponding to hydraulic retention times (HRTs) of 3 and 1.5 hours were achieved for BF1 and BF2, respectively and nitrification efficiencies are close to 98% for the both reactors. The ferrous form of iron was oxidized to the ferric form as a hydroxide (Fe(OH)3), which was mostly washed out. This resulted in a high iron removal efficiency (98%) with effluent suspended solid (3-6 mg/l) containing a low volatile suspended component (20%). Nitrification efficiency decreased sharply due to a decrease in temperature from 25 to 15°C, but efficiency quickly recovered following 1 day of operation, demonstrating that the attached-immobilized nitrifiers in BF reactor were able to adapt to the decrease in temperature. Nitrifying bacteria communities from BF reactors were investigated with rRNA-based molecular techniques, and ammonia oxidizers as Nitrosomonas were found in both reactors. Ammonia oxidizers identified as a Nitrosospira sp. were also found in BF2.
We assessed the primary and ultimate biodegradability in aquatic environments of three phthalic acid esters (PAEs)—di-n-butyl phthalate (DBP), butyl benzyl phthalate (BBP) and di (2-ethylhexyl) phthalate (DEHP)—and phthalic acid (PA) by using microbes obtained from four river-water, three pond-water and four activated sludge samples. Though none of the tested samples had been acclimatized to PAEs, all of them showed an ability to biodegrade the PAEs and PA, suggesting the ubiquitous existence of PAE-degrading microbes in aquatic environments. The PAEs underwent rapid primary biodegradation: 40 and 10 mg · l-1 TOC of the PAEs disappeared within 2 weeks via biodegradation by activated sludge samples and by river- and pond-water samples, respectively. However, ultimate biodegradation reached only 40%-80% by activated sludge and 15%-70% by river- and pond-water samples within the 2-week experimental period, and metabolites accumulated, including monoalkyl phthalates, PA, protocatechuate and β-carboxy-cis-muconate. According to analyses of the biodegradation kinetics, the investigated PAEs can be ranked by their primary and ultimate biodegradability as DBP≥BBP>DEHP and BBP≥DBP>DEHP, respectively.
The disposer wastewater treatment system, which combined with the household garbage disposers and the wastewater treatment equipment, has spread quickly in a metropolitan area. However, wastewater treatment properties of installed systems in a real houses has not been reported yet. In this paper we reported the 4 year survey of the system wastewater treatment properties and its household waste reduction effect. The system has installed for the 48 houses condominium in a major city designated by government ordinance. It was found the BOD and SS influent concentrations were always lower than the design standard concentrations and garbage weights discharged by houses were also 0.6 times as its design standard weight. And then, system effluent concentrations were sufficiently lower than the designed concentrations, 200mg/l. The disposers reduced the household waste to 0.6 times and made ease to classify the recyclable waste by making the rooms for temporary storage until municipal collection.
The anaerobic treatment of wastewater including yeast, Pichia pastoris, with a high concentration of 30 g/l was carried out. To digest the high VSS concentration, a two-phase anaerobic digestion process consisting of liquefaction and gasification was used. Performance of thermophilic liquefaction (53°C) was better than mesophilic liquefaction (37°C) with respect to VSS digestion, using a upflow anaerobic filter reactor. The digestion efficiency of VSS was about 80% at an organic matter volumetric loading rate of 1 to 2 g/l/d. The effluent from the liquefaction process had to be diluted prior to the gasification treatment. The allowable maximum TOC loading rate was only 1 g/l/d to achieve a TOC removal efficiency of more than 80%. It was shown that thiourea inhibited 70% of the gasification performance even at a low concentration of 10 mg/l, and the reason for the inhibition of gasification seems to be the presence of a thiourea-like compound in the wastewater.
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