Soluble microbial products in pilot-scale drinking water biofilters with acetate as sole carbon source.

A comprehensive study on formation and characteristics of soluble microbial products (SMP) during drinking water biofiltration was made in four parallel pilot-scale ceramic biofilters with acetate as the substrate. Excellent treatment performance was achieved while microbial biomass and acetate carbon both declined with the depth of filter. The SMP concentration was determined by calculating the difference between the concentration of dissolved organic carbon (DOC), biodegradable dissolved organic carbon (BDOC) and acetate carbon. The results revealed that SMP showed an obvious increase from 0 to 100 cm depth of the filter. A rising specific ultraviolet absorbance (SUVA) was also found, indicating that benzene or carbonyl might exist in these compounds. SMP produced during this drinking water biological process were proved to have weak mutagenicity and were not precursors of by-products of chlorination disinfection. The volatile parts of SMP were half-quantity analyzed and most of them were dicarboxyl acids, others were hydrocarbons or benzene with 16-17 carbon atoms.

Fate of dissolved organic nitrogen during biological nutrient removal wastewater treatment processes.

Due to its potential to form toxic nitrogenous disinfection byproducts (N-DBPs), dissolved organic nitrogen (DON) is considered as one of the most important parameters in wastewater treatment plants (WWTP). This study describes a comprehensive investigation of variations in DON levels in orbal oxidation ditches. The results showed that DON increased gradually from 0.71 to 1.14 mg l-1 along anaerobic zone, anoxic zone, aerobic zone 1 and aerobic 2. Molecular weight fractionation of DON in one anaerobic zone and one aerobic zone (aerobic zone 2) was performed. We found that the proportion of small molecular weight (<6 kDa) decreased and large molecular weight (>20 kDa) showed opposite trend. This variation may have been caused due to the release of different types of soluble microbial products (SMPs) during biological processes. These SMPs contained both tryptophan protein-like and aromatic protein-like substances, which were confirmed by three-dimensional excitation-emission matrix (EEM) analysis.