ABSTRACT
A kinetic model for multicomponent substrate removal by the partial ozonation process is presented. The model consists of a component describing the co-evolution of COD and BOD as a function of ozone dosage and a mass transfer based component describing ozone dosage as a function of time. A multiple zero order reaction concept is used to describe the multicomponent kinetic behaviour. The model has been verified experimentally by comparing stoichiometric ratio and ozone reaction rate of conventional partial ozonation processes and partial ozonation processes with intermittent biodegradation. The model is found to effectively describe the change in stoichiometry and reaction rate that typically occurs during ozonation processes. Intermittent biodegradation is found to have no effect on the instantaneous stoichiometric ratio or the instantaneous ozone reaction rate. This implicates that intermittent BOD removal results in an additional decrease in required ozonation time and ozone demand compared to the conventional partial ozonation process and in addition to the expected decrease resulting from BOD removal.
Subject(s)
Models, Chemical , Ozone/chemistry , Waste Disposal, Fluid , Water Pollutants, Chemical/isolation & purification , Biodegradation, Environmental , Biological Oxygen Demand Analysis , Diffusion , Hydrogen-Ion Concentration , Kinetics , Oxygen/isolation & purification , Time FactorsABSTRACT
The aim of this work is the Toxicity Identification Evaluation (TIE) of highly toxic tank truck cleaning wastewater effluent. Conventional TIE, using EDTA and activated carbon addition, revealed organic compounds as main source of toxicity. Additional toxicant characteristics could be derived from hydraulic wastewater treatment plant simulation being high intake frequency, low biodegradability and high acute toxicity ratio between Pseudokirchneriella subcapitata and Daphnia magna. The risk probability of compounds present in the influent wastewater was simulated using USEPA Estimation Program Interface (EPI) software. Compound toxicity, solubility and removal rate in a wastewater treatment plant were incorporated into one risk number indicative for the probability of a compound to cause toxicity in the effluent. The herbicide acetochlor was deducted from these TIE procedures as major toxicant and this was confirmed by chemical measurements, concentrations in the effluent samples ranged from 3.73+/-0.52 ppm to 7.8+/-2.1 ppm acetochlor equivalents.
