Journal of Water and Environment Technology Vol. 15(2017) No. 3

The palm oil mill effluent (POME) is generally treated using biological anaerobic treatment and then utilized for POME land application. This research aimed to study the effect of treated POME land application on soil microbial community structure in oil palm plantation and their impact to the oil palm productivity. The results showed that ubiquinone (UQ) and menaquinone (MK) contents in soils without treated POME application were 0.045 and 0.204 μmol/kg-dry soils, respectively. These were much lower than the UQ and MK contents in soils with treated POME application which were 0.074 and 0.301 μmol/ kg-dry soils, respectively. The diversity quinone (DQ) and bioenergetic divergence quinone (BDq) in soils without treated POME application were 11.21 and 0.86, respectively, while in soils with treated POME application were 11.32 and 0.87, respectively. These results indicate that the treated POME application increased the amount of microorganisms but did not change the diversity of microorganisms. Treated POME application also increased the domination of aerobic bacteria in soils. The total UQ, MK, and UQ/MK ratio of soils with treated POME application are higher than those of soils without treated POME application and the application of POME is generally able to increase oil palm productivity.

We analysed the river water quality of Rekifune River and Satsunai River watersheds, which are evaluated as a clear stream in Tokachi region, Japan with the principal component analysis (PCA) and the cluster analysis to interpret complex water quality data and to evaluate factors affecting river water quality on the basis of a 2008 investigation. The mean pH was neutral and stable, also the mean BOD, SS and EC were relatively low. However, T-N concentrations tended to be high in Satsunai River watershed. The PCA and cluster analysis integrated the trend of water quality to two main components and classified the sampling points into three clusters. From the results, the river water quality of Satsunai River watershed was deteriorated by agricultural impacts, whereas the river water quality was preserved in Rekifune River watershed. Furthermore, three sampling points affected by the point source were classified in both river watersheds. It is necessary to develop a framework of agricultural impacts on Satsunai River watershed to improve the river water quality. An equally important priority is to control the loads from agriculture in some parts of Rekifune River watershed to maintain good water quality.

In Japan, there is little knowledge about the reduction in biological effects of wastewater on aquatic organisms by wastewater treatment, and a toxicant(s) contained in wastewater. The purpose of this study was to examine seasonal variation in the biological effect of the influent and final effluent obtained from a wastewater treatment plant, and to characterize the toxicant(s) in the wastewater using an algal growth test. The influents in every season tested had a growth-inhibiting effect on Pseudokirchneriella subcapitata. The final effluent in winter also had the same effect, but the final effluents in other seasons did not. The growth-inhibiting effects of the effluent in winter might be due to a reduction in the biological treatment ability caused by a decrease in water temperature, which may have led to the presence of residue of some toxicants in the effluent. A Toxicity Identification Evaluation (TIE) test suggested that the potential toxicants in the influent were non-polar organic toxicants and surfactants, among others, and that the toxicants in the final effluent were oxidants and pH-dependent toxicants. These potential toxicants appeared to be similar to chemicals suggested by the Pollutant Release and Transfer Register (PRTR) information, implying that this information is useful for identifying toxicants.

Control of non-point source pollution, particularly in terms of nutrients, has advanced to a new phase where the identification of pollution sources and processes is necessary for complex river systems. The Soil and Water Assessment Tool (SWAT) is a process-based model that has been applied to manage aquatic environments in multiple river basins worldwide. In this study, nitrogen (N) loads from point and non-point pollution sources in the Cau River Basin, one of the three most polluted river basins in Vietnam, were simulated. Three scenarios with different combinations of pollution sources were developed to evaluate the major contributions of natural sources, cultivation, industry, households, craft villages and livestock in the study area. A set of hydrological and water quality parameters was successfully calibrated and validated with data observed over multiple years. The model results showed good performance in stream flow simulations at all four hydrological stations. The best performance for the N load simulation was under a scenario representing the dominant contribution of the non-point sources, which caused high amounts of N runoff and was likely triggered by rainfall. The modelling approach presented in this study provides an example for establishing a modelling platform for complex pollution systems.

Recently, perfluorohexanoic acid (PFHxA), an emerging contaminant, has been detected at a high level in the water environment. Its possible presence in drinking water treatment process thus suggests that removal technique should be developed. In this study, one reverse osmosis (RO) membrane, two nanofiltration (NF) membranes and two ultrafiltration (UF) membranes were tested to reject PFHxA (100 − 300 ng/L) in pure water. The measured molecular weight cut-off (MWCO) of two NF membranes were as large as 10,000 and 27,000 Da, while they were still able to reject 96.3% and 95.3% PFHxA in pure water, respectively. This indicates PFHxA rejection rate was not dependent on the MWCO of membrane. Results also show that membrane with more negative zeta-potential tends to have higher rejection rate to PFHxA in pure water, suggesting that electrical repulsion between PFHxA and membrane might play an important role in PFHxA rejection. In conclusion, NF membranes would be a better option for removing PFHxA from drinking water than RO membrane because of their larger pure water permeability and NaCl transmission.