Prediction of the Effect of Recirculation on the Effluent Quality of Anaerobic Filters by Empirical Models

Author： Yu Hanqing Wilson Francis Tay Joo-Hwa

ISSN： 1061-4303

Source： Water Environment Research, Vol.72, Iss.2, 2000-03, pp. : 217-224

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Abstract

The action of effluent recirculation on an anaerobic filter is complex, and there has been no consensus about its effect. In this study two models, established through linear regression analyses of experimental results from two anaerobic filters without recirculation, were modified and used to predict the effect of recirculation on effluent quality of anaerobic filters. The form of the models suggested that effluent recirculation would increase the output chemical oxygen demand (COD) concentration of the anaerobic filter treating municipal wastewater, whereas the effect of recirculation on the anaerobic filter treating soybean processing wastewater would be more complex. For a given raw COD concentration and hydraulic loading rate, it was predicted that there would be a threshold recirculation ratio (r_t) for the anaerobic filter treating soybean wastewater. It was predicted that recirculation with a ratio less than r_t would reduce output COD concentration and enhance performance of the anaerobic fiter, whereas recirculation with a ratio beyond r_t would result in a greater output COD concentration and thus adversely influence performance. Subsequent experiments verified these predictions.