F-specific RNA bacteriophages (FRNAPHs) have been suggested as good indicators of the presence of human enteric viruses in water treatment facilities. The occurrence and reduction of norovirus (NoV) and FRNAPH genotypes in wastewater treatment plants (WWTPs) have been well studied; however, the relationship between these genotypes in WWTPs has not been fully elucidated. Thus, we aimed to investigate the occurrence and reduction of FRNAPH genotypes in an attempt to identify NoV indicators in a WWTP via a 1-year survey. All FRNAPH and NoV genotypes were detected in WWTP influents at high rates (71–100%), including the infectious FRNAPH genotype IV (GIV), which has been rarely detected in previous studies. The reductions of FRNAPH GII and NoV GII during wastewater treatment indicated a relationship between the two (r = 0.69, P < 0.01), and the mean values were not significantly different. These results suggested that FRNAPH GII could be used as an appropriate indicator of NoV GII during wastewater treatment. FRNAPH GI was also found to be an appropriate indicator of viral reduction because of its high resistance to wastewater treatment compared with the other FRNAPH and NoV genotypes; therefore, it can be considered as a worst-case scenario organism.
The outbreak of Cryptosporidiosis in 1996 in Japan is thought to have been enlarged by the proliferation of Cryptosporidium in the water cycle from wastewater to drinking water through the river system. From this experience, the wastewater system must have functions to remove Cryptosporidium oocysts effectively. Efficiencies of wastewater treatment processes to remove oocysts were investigated using pilot plants receiving municipal wastewater. An activated sludge process and a following sand filter showed removal efficiencies of 2 log and 0.5 log, respectively. Poly-aluminium chloride dosage improved the efficiencies by 3 log for the activated sludge process and by 2 log for the sand filter. Chemical precipitation of raw wastewater with poly-aluminium chloride could achieve 1 to 3 log removal according on the coagulant concentration.
When ultrafiltration (UF) membrane processes that are able to effectively reduce viruses are installed in a waste water reclamation system, the security of sanitation safety for water-borne diseases is essential. It is important to understand the behaviour of enteric viruses such as Adenovirus, Rotavirus and Norovirus (NV), the detection rate of which is relatively high in sewage. This study focused on the UF membrane process for the reclaimed water treatment process, and investigated the removal performance in NV type GI and GII in the UF membrane process by performing coagulation and sedimentation as the pre-treatment process in a pilot-plant by considering the concentration fluctuation of the influent. The removal ratio of GI and GII by the UF membrane process alone was 3.3 ± 0.7 Log in GI and 3.6 ± 1.0 Log in GII, and no clear difference in the removal ratio by NV species type was observed. The removal ratio of NV GII was increased by about 0.6 Log on average (4.2 ± 1.1 Log) compared with the UF membrane process only when the coagulation and sedimentation process were conducted as pre-treatment. However, there was no significant difference in the removal of NV GI by conducting the coagulation and sedimentation process.
The outbreak of cryptosporidiosis in Ogose in 1996 forced the wastewater treatment authorities to rethink the level of contamination by Cryptosporidium of wastewater and waters in the watersheds and counter-measures in wastewater treatment plants. A survey of Cryptosporidium concentrations in wastewater and treated wastewater conducted nationwide showed relatively low levels. Also, evaluation of wastewater treatment showed a 2 log oocyst removal with an activated sludge process and an additional 1 log removal with coagulant dosing.
The behaviour of heavy metals was investigated at 22 wastewater treatment plants (WWTPs). In addition, the survey of heavy metal balance was conducted in detail at one WWTP. For the measurement, 22 types of heavy metals were selected from the chemical materials of pollutant release and transfer register (PRTR). There were some heavy metals, which were detected not in wastewater but in dewatered sludge. By means of the detailed survey at one WWTP, 60 to 80% of some heavy metals, such as B, Mn, Co, Ni and Mo, were discharged with treated water. According to the results of PRTR, Zn, B and Mn accounted for a large part of the discharge into the water course. To estimate the behaviour of heavy metals in the environment, leaching tests were applied to the products made of biosolids. During a series of leaching tests for building materials, it was observed that the concentration of heavy metals was very small, but the ratio of increase keeps a constant value. Therefore, it was considered that the acid extractable contents of heavy metal would be important.
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