To recycle water clarifier sludge as a coagulant, we extracted alum from the sludge (hereafter called recovered alum (RA)) and attempted to obtain a high Al concentration and improve RA quality. RA was obtained by acidifying the sludge with concentrated sulfuric acid to adjust its pH below 2, and then centrifuging the mixture and decantating the supernatant. RA contained Al at 0.75-9.4% as Al₂O₃. To obtain a high Al concentration, it was better to use the sludge with a low water content. As impurity concentration increased with Al concentration, we purified RA by coagulating it with the addition of sodium hydroxide and resolubilizing it with the addition of dilute sulfuric acid. We were able to remove T-N, Fe, and Mn in the crude RA at 43.6%, 45.4% and 76.5% respectively by purification. When we used RA to model effluent containing 0.85 mg P·L^-1 and underground water samples containing 1.14-1.52 mg P·L^-1, the phosphorus removal efficiency of RA was essentially comparable with that of commercial alum. RA removed over 90% phosphorus when the PO₄^3-:Al molar ratio was 1:5. As a conclusion, RA is a useful coagulant as long as we pay attention to the dose of contaminants.

View full abstract

The aim of this study is to survey damage reduction of in an aqueous environment using nonionic surfactants and to develop a resourceful system that recovers and recycles. In previous papers, it was reported that a nonionic surfactant in solution can be removed and recovered using a suction filtration packing soil system. In this study, the recovered nonionic surfactant was separated from the alcohol component of the extract, and examined for possible recycling. The result showed that NP10, NP15, and NP20 could be separated from alcohol using an evaporator. The structure of the separated nonionic surfactant showed no change, as determined from the result of NMR analysis. The performance parameters related to detergency, namely, surface tension, osmotic force, critical micelle concentration, dispersion force, and emulsion stability, were examined for the nonionic surfactant. Although a part of surface tension, osmotic force, and the dispersion force had the significant difference as compared with the intact surfactants, these were maintained of the nonionic surfactant even after separating it from alcohol. From these results, it is clear that, if restricted for this model system, recovered nonionic surfactants can be recyclable.

View full abstract

Recently, coastal recreation areas have been polluted by pathogenic microorganisms from human and animal feces. In fact, it has been reported that the risk of infection by pathogens is not negligible in coastal areas. Fecal bacteria (e.g., fecal coliforms (FCs) and enterococci (ENTs)) were monitored on Aoshima Beach, Miyazaki, Japan, to understand the contamination by fecal bacteria, indicating the presence of pathogens in coastal recreation areas. Coastal water samples were collected at 5 stations on Aoshima Beach between May and August, 2010. The FC and ENT counts in coastal water were found to range from below detection limits (BDL) to 1.4×10³ CFU·100 mL^-1 and from BDL to 4.6×10² CFU·100 mL^-1, respectively. The monitoring carried out daily between June 23 and July 21 indicated that the concentrations of both fecal bacteria increased during rainfall, exceeding the guideline levels set by U. S. Environmental Protection Agency (i.e., FC, 800 CFU·100 mL^-1; ENT, 104 CFU·100 mL^-1). However, the high fecal bacterial counts decreased to approximately 10 CFU·100 mL^-1 within 3 days after the rainfall.

View full abstract