Removal of the Inert Organic Fraction of Municipal Wastewater Using the Integrated Activated Sludge/Trickling Filter System

Document Type : Research Paper

Authors

1 Assoc. Prof. of Environmental Health Eng., Facutly of Public Health, Shahrekord University of Medical Sciences, Shahrekord

2 M.Sc. Student of Environmental Health Eng., Faculty of Public Health, Shahrekord University of Medical Sciences, Shahrekord

3 M.Sc. Student of Natural Resources and Environmental Eng., Tarbiat Modares University, Tehran

Abstract

The discharge of phenol and chlorinated compounds, fatty acids, tannin, lignin, and their by-products into receptive waters poses serious hazards for the aquatic life. In this study, the efficiency of a tow-step process of activated sludge-trickling filter (AS/TF) in the removal of inert chemical materials that defy conventional treatment processes was investigated. For this purpose, an integrated activated sludge process (industrial scale) was used sequentially with a trickling filter (pilot scale). Inside a tank with an effective volume of 6.87 m3 was installed 5.78 m3 of polypropylene 2HX media with a specific area of 240 m2/m3. The hydraulic loading rate (HLR) of the trickling filter during the startup period (90 days) was 3.6 m3/h which was raised to 3.6-6 m3/h in the operation period (120 days), with the best effluent quality achieved at HLR=5.4 m3/h. For the purposes of the experiments in this study, four reactors, each 1256 cm3 in volume, were fed the WWTP effluent and concurrently a glucose substrate containing a COD content equal to that fed to the four reactors was fed into two identical reactors; all the reactors were subsequently run for 480 h in aerobic conditions. Nutrients, pH, and DO (as environmental control indicators) as well as soluble and total COD were measured twice daily. The effluent values of soluble inert materials (SI), total soluble COD (STO), degradable suspended materials (XSO), degradable COD (CSO), refractory suspended materials (XI), and degradable soluble materials (SSO) for AS were calculated as 40, 227, 94, 281, 251, and 187, respectively, while the same parameters for the AS/TF were 20, 227, 104, 311, 241, and 207 mg/l, respectively. The results showed that the activated sludge process when combined with the trickling filter has a twofold capability, compared to when used alone, in removing inert COD. It was also shown that treatment levels in conventional WWTPs can be improved by integrating conventional treatment processes.

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