TREATMENT METHODS TO IMPROVE THE ACTIVATED SLUDGE BIODEGRADATION OF A COMPLEX WASTE.

摘要

This research was directed toward enhancing the activated sludge aerobic biodegradation of polynuclear aromatic-type molecules known to be present in the pyrolysis waste as well as other petroleum products. Volatilization, activated carbon adsorption, photolytic activity, microbial seed source, and long solids retention times were the activated sludge treatment enhancers examined under basal and shock-loaded conditions. The two research questions were: Can the complex pyrolysis waste activated sludge biodegradation be improved by applying the treatment methods proposed? Would the treatment effectiveness be supported by toxicity tests on the effluents?; The analytical methods used included chemical oxygen demand (COD), total organic carbon, suspended solids, oxygen uptake rates, electrolytic biological oxygen demands, and acute toxicity tests with Daphnia magna. The three liter activated sludge units were batch fed up to 1500 mg/L soluble COD with 20% pyrolysis waste. Operational variables utilized were 100 mg/L powdered activated carbon (PAC) and 1000 mg/L granular activated carbon (GAC) added to the activated sludge units, an activated sludge unit kept in the dark continuously, four different microbial seed sources, and 10, 20, 40, 80 day solids retention times (SRTs).; Conclusions are: (1) Volatilization with diffused air is effective as a pretreatment method for high loadings of the pyrolysis waste onto the activated sludge system. (2) Minimal amounts of activated carbon are effective in reducing organic content and oxygen demand of activated sludge effluents. GAC was found to be as effective and easier to apply than PAC. (3) An inhibitory effect of photolysis was expressed when the activated sludge units were shock-loaded with pyrolysis waste. (4) The seed sources for activated sludge processing of the pyrolysis waste which were most adaptive were the "virgin" Iowa topsoil and the primary sludge organisms. (5) The longer solids retention times (20, 40, and 80 day SRTs) were significantly more effective in reducing the organics, biologically oxidizable material, and total suspended solids of the pyrolysis waste in the activated sludge process. Toxicity testing with Daphnia magna supported the conclusion that long solids retention times (20 and 40 day SRTs) improve effluent quality and reduce its toxicity.