Performance of single-pass and by-pass multi-step multi-soil-layering systems for low-(C/N)-ratio polluted river water treatment

Chemosphere
Cai-Jie Wei, Wei-Zhong Wu

Abstract

Two kinds of hybrid two-step multi-soil-layering (MSL) systems loaded with different filter medias (zeolite-ceramsite MSL-1 and ceramsite-red clay MSL-2) were set-up for the low-(C/N)-ratio polluted river water treatment. A long-term pollutant removal performance of these two kinds of MSL systems was evaluated for 214 days. By-pass was employed in MSL systems to evaluate its effect on nitrogen removal enhancement. Zeolite-ceramsite single-pass MSL-1 system owns outstanding ammonia removal capability (24 g NH4+-Nm-2d-1), 3 times higher than MSL-2 without zeolite under low aeration rate condition (0.8 × 104 L m-2.h-1). Aeration rate up to 1.6 × 104 L m-2.h-1 well satisfied the requirement of complete nitrification in first unit of both two MSLs. However, weak denitrification in second unit was commonly observed. By-pass of 50% influent into second unit can improve about 20% TN removal rate for both MSL-1 and MSL-2. Complete nitrification and denitrification was achieved in by-pass MSL systems after addition of carbon source with the resulting C/N ratio up to 2.5. The characters of biofilms distributed in different sections inside MSL-1 system well illustrated the nitrogen removal mechanism inside MSL systems. Two kinds of MSLs ar...Continue Reading

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