Preliminary study was done for the two types of wastewater treatment systems: bench-scale combined system of UASB+DHS (upflow anaerobic sludge blanket+downflow hanging sponge) reactor and single DHS reactor. The main objective of this study was to evaluate the prospective combined system of UASB+DHS or single DHS reactor to be applied in Jakarta. The result performance was subsequently compared to the existing intermittent aerobic pond system (IAPS) at the same location. Total COD removal by systems was around 90%, while the IAPS performance achieved only 52%. The organic removal efficiency of the combined system was comparable to that of the single DHS reactor but higher ammonium removal was achieved in the single DHS. Moreover, even though a short hydraulic retention time (HRT) was applied, the treatment performances of both systems were better than that of IAPS in terms of nitrification process. These findings suggest that single DHS reactor can be a viable option for the treatment of domestic wastewater in Jakarta.
A johkasou system is getting popular as a decentralized wastewater treatment system in low-density communities. Treated waters of the johkasou systems, which are generally discharged into channels within residential areas before entering the local receiving water body, may contain microbial contaminants. To identify the characteristics of fecal indicators in the channels of the johkasou systems, the concentrations of fecal indicators (F-RNA bacteriophages, GIII F-RNA bacteriophages, Escherichia coli, and total coliforms) were examined both in water and sediment in the channels of three johkasou systems. These fecal indicators were always detected at high levels both in water and sediment in the channels of three johkasou systems through the study period. Significant differences in concentrations of fecal indicators were not observed among three johkasou systems in different residential areas. Concentrations of fecal indicators fluctuated in a day mainly due to domestic activities. Significant positive correlations of total coliforms and E. coli in water with total coliforms and E. coli in sediment suggest the potential importance of sediment on microbial dynamics in the channels of the johkasou systems. No significant correlations of F-RNA bacteriophages with total coliforms and E. coli indicate a specific distribution mechanism for F-RNA bacteriophages.
This study aims to investigate the distribution of perfluoroalkyl carboxylates (PFCAs) and fluorotelomer alcohols (FTOHs) from air to water environment. Air and rainwater samples were collected in Kyoto, Japan. Eight PFCAs (C5 - C12) and three FTOHs in the samples were quantified by HPLC-MS/MS and GC-MS, respectively. All PFCAs were detected in the air (140 pg/m3) and rainwater (16.4 ng/L) samples, indicating their wet deposition from air in the study area. Flux of PFCAs via wet deposition ranged between 120 - 670 ng/m2 in each rainfall event. All FTOHs were detected in the air (1,800 pg/m3) but they were below the detection limits in rainwater (‹ 6.9 - 8.7 ng/L). The results indicated that FTOHs were difficult to be wet deposited from the air. Most of PFCAs in rainwater increased after a few weeks of sunlight exposure, which suggests degradation of their precursor compounds. Photodegradation of 8:2 FTOH was confirmed by a UV (254 nm) irradiation experiment. Five PFCAs (C5 - C9) were identified as degradation products of 8:2 FTOH, with the production rate of 1.79% at molar basis. This study demonstrated distribution pathways of PFCAs and their precursors in environment via wet deposition and photodegradation, and confirmed that atmosphere is an important compartment for the distribution of these compounds to water environment.
In a mesophilic anaerobic digestion process, decayed waste activated sludge biomass fed to a digester formed soluble COD substrates, which were eventually converted to methane by anaerobic microorganisms. To improve the decomposition of the soluble materials, performance of a high-rate anaerobic digester was experimentally evaluated. A lab-scale moving-bed biofilm digester having 83.33 m2-carrier surface/m3-reactor was operated for 200 days with decreasing HRT from 20 days to 1 day, while comparing its response to a conventional chemostat digester. Although both reactors gave a comparable methane production until a 15-day HRT, the soluble TOC in the chemostat digester elevated to 3,000 mg/L at 4-day HRT suggesting washout of the anaerobic microorganisms. On the other hand, the moving-bed biofilm digester kept a reasonable methane production rate without accumulation of the soluble materials until 3-day HRT. When the HRT was reduced to 2 days, the soluble fraction decreased due to limited production of the decayed materials. To simulate the responses, an extended IWA-Activated Sludge Model was applied and individual kinetics were estimated. The simulation demonstrated that the relevant active anaerobic biomass (acidogens and methanogens) accumulated in the moving-bed biofilm digester showing high TVS digestion efficiency (25%) at even very short HRT.
Adenoviruses, the most UV resistant microorganism currently known, are posing concerns in UV treated drinking water. To reduce the risk from adenovirus infection, combination processes of UV and chlorination are attractive. Bacteriophage MS2 and adenovirus 5 (AdV5) were used in this study, and inactivated by low-pressure UV (LPUV) lamp, chlorination, sequential processes (UV-Cl2 and Cl2-UV) and a simultaneous process (UV/Cl2). MS2 was more resistant against chlorine than AdV5, and CT values for 2 log reduction of MS2 and AdV5 were 0.77 and 0.033 mg-min/L, respectively. However, AdV5 was more resistant to UV than MS2 and required a 101 mJ/cm2 of fluence for 2 log reduction. Compared to the application of UV or chlorine separately, an increasing trend of MS2 inactivation rate was found in the sequential processes, which was statistically significant (p ‹ 0.05, ANCOVA). The simultaneous process of UV/Cl2 for MS2 provided about 2.3 times higher inactivation rate than a summation of inactivation rates by the separate application of either chlorine or UV, even at the same UV fluence rate and the same initial chlorine concentration. The combination processes of UV and chlorine, either sequential or simultaneous application, seemed to be more effective than a standalone process in viral inactivation.