Industrial wastewaters have been strongly controlled by effluent standard. Either water quality-based or technology-based effluent standard could be adopted on the basis of the scientific rationale. Since it is important to set the regulation acceptable to both of environmentalist and developmentalist, reasonable background in areal classification and industrial categorization is required as well as scientific background. This study focused on Korean effluent standards from the past to the future covering how to set the regulation based on the approaches employed in well-developed countries. Except the area where strong protection is required, the regulation should be applied according to the type of discharge, that is, direct or indirect discharge. Industrial categorization should be carried out with the collection of wastewater data to reflect the characteristics of wastewater in the regulation. As a way of improving the allowable level of pollutant discharged, it was proposed that conventional pollutants to follow technology-based standard, whereas toxic pollutants would be appropriate to water quality-based standard. The lognormal distribution based on the effluent concentration data was considered to be reasonable for the regulation of conventional pollutants. The water quality standard implying risk assessment with 10 times dilution ratio was used to derive toxic pollutant standards.
With increasing concerns regarding the limited capacity of landfill, conservation of resources, and reduction of CO2 emissions, dry anaerobic digestion of organic solid waste has recently been gaining considerable attention. However, there have been few reports on continuous operation and most have involved operation under thermophilic condition. In the present study, a continuous dry anaerobic digestion system treating a mixture of food waste and paper waste was operated under mesophilic condition. For easy injection of a solid type substrate, the feed was diluted six-fold with the sludge inside the reactor, and then, fed into the reactor. During the operation, hydraulic retention time (HRT) decreased as follows: 150, 100, 60, 40, and 30 d at a fixed substrate concentration of 30% total solids (TS), corresponding to a solid loading rate (SLR) of 2.0, 3.5, 5.0, 7.5, and 10.0 kg TS/m3/d, respectively. Up to 40 d of HRT, biogas production proportionally increased as SLR increased, but at 30 d of HRT, biogas production decreased. At further operation, instead of controlling HRT, substrate concentration was increased to 40% TS, which was found to be a better option for increasing the treatability. The system could achieve a stable CH4 production yield of 0.27 m3 CH4/kg TSadded and 0.25 m3 CH4/g CODadded, and over 75% of volatile solids (VS) reduction.
A novel high-dissolved CO2 device was developed for the disinfection of treated sewage wastewater. Several experiments were conducted regarding the waterborne pathogen inactivation rate, the treatment time and the disinfection target (several treated sewage wastewaters, canal and river water). The results indicated that different disinfection targets can lead to 2.8-3.0 log-inactivation of waterborne pathogens within 20 minutes of treatment under 0.3 MPa of pressure in the device. Results also showed that the suspended solid (SS) in raw water affected the disinfection efficiency.
In this study, it was attempted to identify the mutagen produced by chlorination of insecticide fenitrothion using a quadrupole GC-MS and a high-resolution GC-MS. From the mass spectra obtained by the GC-MS, the chemical structures of two unidentified compounds were extrapolated: one was identified as 2-chloro-5-methyl-4-nitrophenol by comparison to the synthesized standard compound, while another one was identified as trichloro-3-methylphenol by high-resolution GC-MS. The mutagenicity of these identified chlorination by-products (CBPs) of fenitrothion were evaluated by the Ames assay (preincubation method) using Salmonella typhimurium TA100 without exogenous activation by S9 mix (TA100-S9). However, none were found to be mutagenic. Further studies are needed to identify the mutagenic CBP(s) of fenitrothion.
A rapid decrease in the concentration of microcystin due to the decline of Microcystis spp. cells has been observed during fall in Japan. Past researches have shown the involvement of microcystin-degrading bacteria in this phenomenon, but the process by which it occurs has not yet been elucidated. In this research, microcystin-degrading bacteria were quantified using real-time TaqMan polymerase chain reaction. The new TaqMan probe was based on the sequence of the mlrA gene that is conserved in microcystin-degrading bacteria; new primers were similarly developed. These new primers and probe enabled the precise examination of microcystin-degrading bacteria in a biofilm. Moreover, the bacteria present in a biofilm from a practical biological treatment facility could be detected and quantified. The results showed that microcystin-degrading bacteria existed in the biofilm throughout the year, and the number of bacterial cells increased in fall.
The mixture of polysilicate and Fe(III), and commercial polysilicato-iron (PSI) were employed to control membrane fouling risk. Batch experiments and long-term membrane bioreactor (MBR) experiments were conducted with the addition of 1) polysilicate, 2) mixtures of polysilicate and Fe(III) with various ratios, and 3) sole Fe(III) and commercial PSI with two available molar ratios, Fe/Si = 1:1 (PSI-100) and Fe/Si = 1:0.25 (PSI-025). Sole polysilicate addition in MBR showed no effect on controlling membrane fouling risk, while the mixture of polysilicate and Fe(III) could yield some advantages at a specific combination, 90 mg/L Fe(III) with 5 mg/L Si for batch experiment, and 45 mg/L Fe(III) with 20 mg/L Si for long-term MBR experiment. On the other hand, the higher efficiency of biopolymer removal was attained by the addition of PSI in batch experiments. Furthermore, the membrane fouling frequencies were reduced and the concentrations of protein and carbohydrate in soluble microbial products (SMP less than 1μm) were largely diminished by the addition of PSI in long-term MBR experiments. These results suggested that PSI would be useful to control membrane fouling problem and enhance the performance of membrane filtration.
Fenthion (MPP), an organophosphorus pesticide, is widely used as an agricultural and household insecticide. The oxons are known to be the actual toxic forms of organophosphorus pesticides. Using an in vitro cytochrome P450 (CYP) metabolism system, MPP was metabolized to produce five metabolites: MPP sulfoxide, MPP sulfone, MPP oxon, MPP oxon sulfoxide and MPP oxon sulfone. MPP sulfoxide was the main product, while MPP oxon sulfone and the other metabolites were produced in small amounts. On the other hand, MPP was converted to MPP oxon sulfone by chlorination in a water purification system, raising the possibility of human exposure to MPP oxon sulfone through drinking water. MPP oxon sulfone showed the highest acute toxicity among MPP and its metabolites. In addition, MPP oxon sulfone was not metabolized by CYP3A4, the major CYP isomer in humans. It is important that MPP and its oxides are monitored and their health risk assessed to control drinking water safety because MPP was detected in river water.
The water quality of environmental waters from the viewpoint of aquatic ecotoxicity was investigated using a three-species ecotoxicity test (algae, daphnia and fish). Water samples were collected, concentrated with a solid-phase extraction technique and exposed to each test species. The growth inhibition, immobilization (swimming inhibition) and mortality ratios in acute toxicity tests for algae, daphnia and fish, respectively, were used as water quality indexes. For the river waters, 38% of the monitoring sites showed good water quality from the viewpoint of long-term ecotoxicity for all the three test species because no toxicity effects were observed at the concentration factors of 10, 50 and 50 for algae, daphnia and fish, respectively. For the agricultural drains, the ecotoxicity level responded sensitively especially when agricultural chemicals were applied. The GC/MS analysis also confirmed that the detection index (DI) in the agricultural drains was often raised significantly by the agricultural chemicals, but the period with high ecotoxicity did not continue for long.
In Japan, environmental quality standards for Zn pollution were enacted recently because of the toxicity of Zn to aquatic ecosystems. A free-water-surface constructed wetland (500 m2) planted with Zizania latifolia Turcz. received secondary-treated wastewater from a dormitory (60 to 100 residents) at the Koibuchi College of Agriculture and Nutrition in Japan, to remove nutrient salts before the discharge of the water to a pond for agricultural use. We examined the removal efficiencies of Zn and its behavior in this constructed wetland within 3 years and discussed the mechanism of Zn removal. The constructed wetland was effective in treating wastewater with low Zn concentrations. The T-Zn concentration in secondary-treated domestic wastewater (average T-Zn: 0.048 mg/L) decreased by 51% during passage through the constructed wetland. Most of the dissolved Zn was removed, but only a little particulate Zn was removed. The increase in Zn concentration in the wetland soil corresponded to 69.8% of the Zn removed by the wetland. However, the amount of Zn accumulated in the aboveground parts of Z. latifolia corresponded to only 9.8% of the Zn removed by the wetland. Thus, Zn was removed mainly by adsorption onto the wetland soil, including soil particles and organic matter.
We investigated the stability of the phenol-removal ability of an association between Spirodela polyrrhiza and bacteria. We carried out 21-cycle repeated batch experiments (equivalent to 21 days where each cycle was done for 24 hours) on phenol-contaminated water treatment using S. polyrrhiza-pond water bacteria association and pond water bacteria alone. The rate of phenol degradation by the S. polyrrhiza-bacteria association was higher than that by the pond water bacteria alone through the 21 cycles. The phenol degradation ability of the S. polyrrhiza-bacteria association rapidly increased after exposure to phenol, along with a notable increase in the density of catechol 2,3-dioxygenase (C23O) gene in the bacterial community. S. polyrrhiza-bacteria association rapidly gained an enhanced phenol degradation ability compared with the pond water bacteria alone. After phenol acclimation, this enhanced phenol degradation ability of S. polyrrhiza-bacteria association was maintained in the long term, with a high density of catechol 1,2-dioxygenase (C12O) gene and C23O gene in the bacterial community. Bacteria harboring a diverse range of C12O gene and C23O gene accumulated on the root of S. polyrrhiza, and bacterial diversity was stable under conditions of phenol contamination. The findings in this study demonstrate the possibility of using an aquatic plant treatment system as an effective and stable treatment technology for organic pollutants.
In this study, the formation characteristics of aerobic granular sludge in a continuous-flow reactor were investigated under several experimental conditions. Both surface loading rate (equal to liquid linear velocity at a sludge settling zone) and aeration rate strongly affected the selection of well-settling sludge in the same manner as sludge settling time in a sequencing batch reactor. By setting and controlling adequate surface loading and aeration rates, small particles were effectively washed out, and well-settling sludge selectively remained in the reactor. As a result, aerobic granular sludge was effectively formed. On the other hand, feeding pattern, i.e., continuous and intermittent feeding, did not affect the aerobic granulation when completely inorganic wastewater was fed. These findings will contribute to the dissemination of aerobic granular sludge technology because the information on the formation of aerobic granular sludge in a continuous-flow reactor is limited.
In Hanoi, the capital of Vietnam, lakes and rivers are polluted by both point pollution sources such as discharge from sewerage system; and by non-point pollution sources such as washoff from land surface and leakage from septic tanks. Several studies had mentioned about water pollution but were mainly focusing on organic pollution, feacal contamination and pollutant sources from surface runoff were not considered. To investigate the characteristics of pollutant variation in runoff water and feacal contamination by pathogenic indicators, water samples were collected in August and September 2008, by the roadside and at the inflows of lakes under wet weather condition in the downtown of Hanoi. Monitoring results showed high pollutant concentration, especially pathogenic indicators as E.coli and total coliform (TC), both in road runoff and water that flowed into lakes. Runoff water quality was much different depending on the sampling locations and patterns of rainfall. Pollutant concentration collected by the roadside tend to increase at the end of rainfall. It might be attributed to the discharge of domestic wastewater from individual households or leakage from septic systems. Time and spatial variation were much different for each event that made urban runoff water to be more difficult to control in comparison with domestic wastewater. Cluster analysis was applied to find the similarities of water quality among sampling locations. It was a useful method to find the spatial variation of pollutants and their level of pollution.