Formation and Role of Bacterial Community in the Sediment Bed of Open Channel Receiving Johkasou Effluent: Multivariate Statistical Analysis Interpretation

Abstract

To obtain information that can be used as reference for improving the environment inside and surrounding the open channels receiving johkasou effluent, the formation and correlation of sediment bed bacterial density with water quality were evaluated with multivariate statistical analysis based on measured data for water and sediment samples collected for 8 times from 6 sites of an open channel that receives johkasou effluent in a residential area of Gifu Prefecture, Japan. Statistical analysis included principal component and factor analysis (PCA/FA), cluster analysis (CA) and correlation analysis. The PCA/FA results showed that 3 dominant factors were responsible for the water quality data structure, accounting for 85.12% of the total variance in the dataset. Hierarchical cluster analysis grouped 6 study sites into 3 statistically significant clusters, reflecting different characteristics and pollution levels of the sites. Correlation analysis revealed statistically significant relationships of the sediment bed bacterial density with BOD, total nitrogen and total phosphorus in the water of the channel receiving johkasou effluent.

Spatialand Temporal Variation in Concentration of F-Specific Rna Bacteriophages in an Open Channel Receiving Johkasou Effluents

“…The interactions between the viruses in the water and the viruses in the sediment, intended as attachment of the viruses onto the sediment particles and their re-suspension from the sediment bed into the water phase, possibly occurred due to the strong correlation between F-RNA bacteriophages in the water and Qβ in the sediment and to the significantly positive correlation of F-RNA bacteriophages in the water with the VS and DS. As suggested by Rehmann and Soupir (2005), the re-suspension of microbes from the sediment bed can be a major source for the stream water 8,36) . Previous studies have also shown that the water flow over the sediment can affect the vertical diffusive flux of solutes because the solute concentration profile near the sediment/water interface varies with the flow velocity 8,37) .…”

“…Correlation analysis was performed using the non-parametric Spearman's rank correlation as not to assume normality of any parameters 24) . The terms "strong", "moderate", and "weak" were applied to factor loading and absolute loading values >0.75, 0.75-0.50, and 0.50-0.30, respectively 8) . All tests were carried out at 5% significant level.…”

“…Human enteric viruses generally enter the water environment through the discharge of sewage-contaminated water 1) . In Japanese rural areas, where sewage systems are not available, a small-scale onsite wastewater treatment system for household wastewater, namely johkasou, has been widely applied 7,8) . Currently, more than eight million johkasou are under operation, which include tandoku johkasou (67%, 5.6 million units) and gappei johkasou (33%, 2.8 million units) 8) .…”

“…Gappei johkasou treats both black and grey water, is an improvement over the tandoku johkasou. It serves approximately forty million people 8,9) . In order to meet Japan's regulation standards, tandoku johkasou was banned for new installation by the Japanese government in 2001 10) .…”

“…It is thus estimated that approximately 20% of the remaining viruses are discharged into the aquatic environment. The effluent can contribute to maintain sufficient water in open channels, enhancing the water circulation in the local areas, and contributing to the life of the aquatic organisms 8) . In addition, open channels receiving the effluents from johkasou may play a role in the transmission of several contaminants into the aquatic environment downstream, including viruses that cannot be completely removed by the johkasou system 11,12) .…”