Characteristics and transformations of dissolved organic nitrogen in municipal biological nitrogen removal wastewater treatment plants

Dissolved organic nitrogen (DON) represents most of the dissolved nitrogen in the effluent of biological nitrogen removal (BNR) wastewater treatment plants (WWTPs). The characteristics of wastewater-derived DON in two different WWTPs were investigated by several different methods. The major removals of DON and biodegradable dissolved organic nitrogen (BDON) along the treatment train were observed in the anaerobic process. Dissolved combined amino acids (DCAA) and dissolved free amino acids (DFAA) in the effluent accounted approximately for less than 4% and 1% of the effluent DON, respectively. Approximately half of wastewater-derived DON was capable of passing through a 1 kDa ultrafilter, and low MW DON cannot effectively be removed by BNR processes. More than 80% of effluent DON was composed of hydrophilic compounds, which stimulate algal growth. The study provided important information for future upgrading of WWTPs or the selection of DON removal systems to meet more demanding nitrogen discharge limits

A 100 Year Sedimentary Record of Heavy Metal Pollution In a Shallow Eutrophic Lake, Lake Chaohu, China

This study has worked on the evaluation of the temporal and spatial evolution of heavy metal contamination in sediment taken from a shallow eutrophic lake, Lake Chaohu, China, over the last 100 years, and thereby used (137)Cs and (210)Pb dating, a PIRLA procedure, statistical analysis, geochemical normalization and a enrichment factor calculation (EF). Concentrations of 5174, 29 325, 10.7, 36.4, 20.4, 386.0, 21.1 and 38.4 mg kg(-1) for Ti, Fe, Co, Cr, Cu, Mn, Pb and Zn, respectively, are proposed as natural background values for the Lake Chaohu based on a PIRLA procedure. The contamination history from the last 100 years can be divided into two periods. Before the 1960s, heavy metal contamination did not occur and there was no spatial difference for heavy metal distribution. Since the 1960s, heavy metal enrichment and contamination has occurred, and the west half of the lake region showed a higher degree of contamination than the east half to various intensified anthropogenic activities. In the east half of the lake region, the anthropogenic source of heavy metals mainly originated from agricultural intensification, whereas in the west half of the lake it originated from city runoff and industry as well as agriculture. In all anthropogenic heavy metals, Co is only from industry

A 60-Year Sedimentary Record of Natural and Anthropogenic Impacts on Lake Chenghai, China

Recent sediments from Lake Chenghai, China, were investigated at high temporal resolution to trace both natural and anthropogenic effects on the lake using total organic carbon (TOC), total nitrogen (TN), total phosphorus (TP), organic phosphorus (P-o), inorganic phosphorus (P-i) and organic carbon and nitrogen stable isotopes (delta C-13(org), and delta N-15) in a Cs-137-dated sediment core. The results indicated that the sedimentary record covers the last 60 years, during which the lake had undergone apparent changes in nutrient sources and productivity in response to nutrient loading. Prior to the late 1980s, the nutrient contents in sediments mainly originated from algae and lake productivity was relatively stable. Since the late 1980s, increasing TOC, TN and TP concentrations together with the change of delta C-13(org) and delta N-15 suggested anthropogenic perturbations in nutrient loading and lake productivity. Endogenic nutrients derived from algae and anthropogenic inputs were two important sources of sedimentary nutrients. The anthropogenic nutrients mainly originated from the discharge of industrial wastewater and artificial cultivation of Spirulina after the middle 1980s, and domestic wastewater discharged from Yongsheng County since 1993