Pilot-Scale Airlift Bioreactor with Function-Enhanced Microbes for the Reduction of Refinery Excess Sludge.

Hongyan Mu,Zhongzhi Zhang,Qingzhe Jiang,Min Zhang,Shanshan Sun,Zhaozheng Song,Yijing Luo

doi:10.3390/ijerph18136742

Abstract

A pilot-scale airlift bioreactor (ALBR) system was built and operated continuously for refinery excess sludge (RES) reduction. Combined ALBR and function-enhanced microbes (composed of photosynthetic bacteria and yeast) were integrated into the system. The pilot-scale ALBR was operated for 62 days, and the start-up time was 7 d. Continuous operation showed that the sludge reduction efficiency was more than 56.22%, and the water quality of the effluent was satisfactory. This study focused on investigating the effects of hydraulic retention time (HRT) on the stability of the system and the effect of sludge reduction. Under different HRT conditions of 40, 26.7, 20, and 16 h, the sludge reduction rates reached 56.22%, 73.24%, 74.09%, and 69.64%, respectively. The removal rates of chemical oxygen demand (COD) and total nitrogen (TN) decreased with decreasing HRT, whereas the removal rate of NH4+-N increased. The removal rate of total phosphorus (TP) was approximately 30%. Results indicate that the ALBR and function-enhanced microbe system can reduce sludge and treat sewage simultaneously, and the effluent is up to the national emission standard. Addition of function-enhanced microbes can promote the degradation of petroleum hydrocarbon substances in the sludge, especially alkanes with low carbon numbers. This study suggests that the optimal HRT for the system is 16 h. The total operation cost of the ALBR combined with the function-enhanced microbe system can be reduced by 50% compared with the cost of direct treatment of the RES system.

Highlights

Refineries produce large amounts of sludge throughout the entire process of crude oil exploration until final refinement [1]
Combined airlift bioreactor (ALBR) and function-enhanced microbes were integrated into the system used for Refinery excess sludge (RES) reduction
Continuous operation showed that the sludge reduction efficiency was higher than 56.22%, and the water quality of the effluent was satisfactory

Summary

Introduction

Refineries produce large amounts of sludge throughout the entire process of crude oil exploration until final refinement [1]. Sludge from petrochemical refineries is a state-specified hazardous waste that has been included in the National Catalogue of Hazardous Wastes in China (2016 edition). Of the total treatment wastewater quantity, the moisture content is usually approximately. The cost of sewage sludge treatment and disposal is over half of the total cost of wastewater treatment plants [3]. The sludge usually contains considerable amounts of toxic and harmful substances, such as parasite eggs, pathogenic microorganisms, heavy metals, and unstabilized organic matter [4,5]. If sewage sludge directly enters the ecological environment without proper treatment and disposal, it will cause secondary pollution and pose a serious threat to human health

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