Showing papers by "Swiss Federal Institute of Aquatic Science and Technology published in 1978"

Tetrachloroethylene in contaminated ground and drinking waters.

Abstract: Chlorinated compounds derived from C 1 and C 2 hydrocarbons are manufactured industrially in quantities exceeding a total annual world production of 36"106 tons. More than 4"106 tons are used either as aerosol propellants or as solvents in dry cleaning and metal degreasing (PEARSON and McCONNELL 1975). Because of their dispersive use and biological resistance these compounds have been identified in various parts of the atmospheric and aquatic environment. Of particular interest is their occurrence in finished drinking waters, where some (e.g. chloroform and other trihalomethanes) are attributed to the impact of water chlorination, and others (e.g. carbon tetrachloride) must be derived from contamination of the raw waters (SYMONS et al. 1975).

Design of a nitrifying activated sludge process with the aid of dynamic simulation

Abstract: A dynamic model of nitrification in the conventional, completely mixed activated sludge process was developed which considers diurnal and daily variations in temperature, hydraulic flow, ammonia load, organic load, sludge wasteage, recycle flow etc. The model is verified with data collected in large scale pilot work with nitrifying activated sludge plants during a six month winter operating period at an average temperature of about 10°C. Three activated sludge plants treating approximately 100 m3 per day of domestic wastewater from the City of Zurich's main sewer were operated at different sludge ages between 2.5 and 10 days. The nitrification model was expanded to predict ammonium concentrations in the receiving water when the degree of nitrification of waste water varies.