Use of dewatered sludge as microbial inoculum of a subsurface wastewater infiltration system: effect on start-up and pollutant removal

Yingying Jiang,Yafei Sun,Yang Zhang,Jing Pan

doi:10.4314/wsa.v43i4.07

Yingying Jiang, Yafei Sun + Show 2 more

Open Access

https://doi.org/10.4314/wsa.v43i4.07

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Journal: Water SA	Publication Date: Nov 6, 2017
Citations: 7	License type: cc-by

Affiliation: Shenyang Normal University

Abstract

Brown earth–based subsurface wastewater infiltration systems (SWISs) inoculated with/without dewatered sludge were constructed and operated under the same conditions to boost the application of SWIS in brown soil areas. Start-up period of SWIS with dewatered sludge was 28 days, 12 days shorter than that of SWIS without dewatered sludge. COD, NH 3 -N and TN removal efficiencies of dewatered sludge as microbial inoculum for SWIS were higher than that of SWIS without dewatered sludge under hydraulic loading rates (HLR) of 0.04, 0.07, 0.1 and 0.13 m 3 ·m −2 ·d −1 . Effluent concentrations of COD, NH 3 -N and TN in the SWIS inoculated with dewatered sludge were 44.51±4.13, 7.35 ± 0.24 and 14.03 ± 0.31 mg·L −1 under HLR of 0.13 m 3 ·m −2 ·d −1 , which were simultaneously lower than Chinese criteria for water discharge from municipal wastewater treatment plants. The number of bacteria, nitrifying bacteria and denitrifying bacteria in dewatered sludge as microbial inoculum for SWIS were higher than that in SWIS without dewatered sludge under the same HLR. The results will be helpful in promoting the application of dewatered sludge as microbial inoculum in brown earth–based SWISs for the purpose of shortening start-up period, effecting high levels of pollutant removal and recycling waste. Keywords : subsurface wastewater infiltration system, dewatered sludge, start-up, inoculum

Highlights

Decentralized wastewater treatment is becoming ever more critical because 95% of decentralized wastewater around the world is currently discharged into the environment without any treatment (Li et al, 2011b)
The start-up period of brown earth–based Subsurface wastewater infiltration systems (SWIS) inoculated with dewatered sludge was 28 days, 12 days shorter than that of the SWIS inoculated without dewatered sludge
COD, NH3-N and TN removal efficiencies for the SWIS using dewatered sludge as microbial inoculum were higher than that for the SWIS inoculated without dewatered sludge, under hydraulic loading rates (HLR) of 0.04, 0.07, 0.1 and 0.13 m3·m−2·d−1

Summary

Introduction

Decentralized wastewater treatment is becoming ever more critical because 95% of decentralized wastewater around the world is currently discharged into the environment without any treatment (Li et al, 2011b). SWIS has many advantages compared with conventional wastewater treatment plants, including high removal efficiency for organics and phosphorus, low construction and operation cost and easy maintenance (Li et al, 2011a). It is widely used in North America, Europe and Asia (Li et al, 2011b). The maximum wastewater hydraulic loading rate of SWIS differs across locations because of differences in the soil matrix and degree of pre-treatment. There are no general recommendations for the maximum number of inhabitants for the application of SWIS. In China, the maximum number of inhabitants for the application of SWIS (800 m3·d−1) is reported by Li et al (2012) to be 8 000 (Li et al, 2012)

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