This paper concerns field survey and laboratory experiment on the inactivation of pathogenic bacteria during sludge treatment processes with particular emphasis on anaerobic digestion process. We surveyed the inactivation of pathogenic bacteria processes by sampling various types of sludges from 17 wastewater treatment plants located in Japan and counting the number of bacteria in the sampled sludges. The bacteria we counted included fecal coliform groups, enterococcus and salmonella. The median number of fecal coliform groups in primary sludge was found to be 105 MPN/g, while the number of fecal coliform groups in digested sludge decreased to 103 MPN/g. We also confirmed that the treatments of dewatering using inorganic coagulant, drying and composting are also effective in inactivating pathogenic bacteria. In addition, we studied the performance conditions of anaerobic digestion and the degree of inactivation of pathogenic bacteria in the experiment of anaerobic treatment of the primary sludge. This study showed that the number of fecal coliform groups in mesophilic digestion sludge was in the range of 102 to 104 MPN/g regardless of the HRT, whereas the number of bacteria in thermophilic digestion sludge was of the order of 100 MPN/g, clearly indicating that the number of bacteria substantially decreases when the sludge is digested at thermophilic temperature. The number of enterococcus in digested sludge was in the range of 102 to 105 MPN/g after the sludge was subjected to mesophilic digestion while the number decreased to 100 MPN/g after the sludge was digested at thermophilic temperature. The number of salmonella in digested sludge was in the range of 1.8 to 30 MPN/4g after the sludge was digested at mesophilic temperature, but the number decreased to less than 1.8 MPN/4g after the sludge went through thermophilic digestion process. The thermophilic digestion is thus effective in inactivating pathogenic bacteria.
The in vitro estrogen receptor (ER) reporter gene assay has long been used to measure estrogenic activity in wastewater. In a previous study, we demonstrated that the assay represents net estrogenic activity in the balance between estrogenic and antiestrogenic activities in wastewater. However, it remained unclear whether the net estrogenic activity measured by the in vitro ERα reporter gene assay can predict the in vivo estrogenic effect of wastewater. To determine this, we measured the following: estrogenic and antiestrogenic activities of wastewater and reclaimed water by the in vitro ERα reporter gene assay, expression of vitellogenin-1 (vtg1) and choriogenin-H (chgH) in male medaka (Oryzias latipes) by quantitative real-time PCR, and estrone, 17β-estradiol, estriol, and 17α-ethynylestradiol concentrations chemically to predict estrogenic activity. The net estrogenic activity measured by the in vitro medaka ERα reporter gene assay predicted the in vivo vtg1/chgH expression in male medaka more accurately than the concentrations of estrogens. These results also mean that in vivo vtg1/chgH expression in male medaka is determined by the balance between estrogenic and antiestrogenic activities. The in vitro medaka ERα reporter gene assay also predicted in vivo vtg1/chgH expression on male medaka better than the human ERα reporter gene assay.
To elucidate the action mechanism of environmental androgenic chemicals on fish reproductive activity by transient stimulation in heavily polluted areas, individuals of the hermaphrodite fish Kryptolebias marmoratus were injected once with six concentrations of methyltestosterone (MT) (0.1, 1, 5, 10, 50, and 100 μg/g BW) intraperitoneally. The fish were sampled at intervals of 7, 15, and 30 days after a single injection. At 7 days after injection, mature oocytes were not observed in the MT-exposed groups except for the group exposed to 0.1 μg MT, while testicular development was not remarkably different between any of the groups. Also, at 7 days after injection, hepatic estrogen receptor α (ERα) and vitellogenin (VTG) mRNA abundance decreased significantly in the MT-exposed groups despite no significant difference in plasma 17β-estradiol (E2) levels between any of the groups. This significant difference in VTG mRNA between the control and the MT-exposed groups persisted until 30 days after injection, although ERα mRNA abundance was not statistically different between any groups at 30 days after injection. Our results clearly show that a single injection of MT inhibits ovarian development rather than testicular development in the hermaphroditic gonad of K. marmoratus. Furthermore, our results demonstrate that a single injection of MT interfered with hepatic VTG mRNA synthesis mediated by the suppression of hepatic ERα mRNA transcription.
The objective of this work was to evaluate the biological effect of the secondary effluent (SE) of a wastewater treatment plant and reclaimed water treated via ultrafiltration (UF) followed by either reverse osmosis (RO) membrane filtration or nanofiltration (NF) to be used for environmental use by comparing the results of algal growth inhibition tests of concentrated samples of the SE and permeates of RO and NF with those of six rivers in southern Okinawa Island. Although the SE water had no adverse effects on the growth of the algae Pseudokirchneriella subcapitata, it could lead to water quality degradation of rivers in terms of its toxic unit value, whereas the use of RO and NF permeates would not lead to such degradation. The recharge of rivers, into which domestic wastewater and livestock effluents might be discharged in southern Okinawa Island, with reclaimed water subjected to advanced treatment could dilute the concentrations of chemicals that cause biological effects and improve the water quality of the rivers, based on the results of the bioassay using P. subcapitata. Comparing the results of bioassays of reclaimed water with those of the ambient water at a site might be effective in assessing the water quality of reclaimed water for environmental use at the site.
The purpose of this study is to evaluate a biological effect of infl uent, secondary and fi nal effl uent obtained by conventional activated sludge process on aquatic organisms. Biological tests were conducted using 3 kinds of aquatic organisms Pseudokirchneriella subcapitata, Daphnia magna and Danio rerio referring to the draft Japanese Whole Effl uent Toxicity test guidelines. These tests were repeated twice for D. magna, three times for P. subcapitata and D. rerio. As a result, some infl uents had some effects on all of the organisms, but secondary and fi nal effl uents had no effect. These results suggested that biological impacts by sewage water were improved by the process, and that chlorination in this study maximum total chloride concentration: 0.87mg/l for P. subcapitata, 0.37mg/l for D. magna and 0.55mg/l for D. rerio had no harmful effect on the organisms.
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