Effect of sponge media structure on the performance of the intermittent contact oxidation process for in-sewer purification

Abstract

We examined the effect of sponge media structure, focusing on the pore cell density and media thickness, on the degradation rates of a model lipid substrate during extended conditions without flow in the intermittent contact oxidation process (ICOP). Three open-celled sponges with approximate cell densities of 6 cell/cm, 9 cell/cm, and 18 cell/cm were used as test sponges. The degradation behavior of lipid substrate placed on a substrate sheet was observed together with a test sponge. Substrate sheets placed at the bottom and on the top of the test sponges were observed separately. Degradation was observed during extended conditions without wastewater flow. The degradation rates had a range of 1.4–7.1 g COD/(m2 ∙ day) for the bottom substrate placement condition and 8.0–12.7 g COD/(m2 ∙ day) for the top substrate placement condition expressed per area of substrate sheet. We found that the direct access of the biofilm to the headspace-gas enhanced degradation rates. To this, increased water retention by increased media pore cell density and thickness decreased the degradation rates. The rate decrease was further associated with the decrease of microbial cell density in the substrate sheet with increased water retention capability of the sponge media.