Sulfate Reduction in an Upflow Anaerobic Sludge Blanket Bioreactor and Optimization of Operational Conditions: pH, Hydraulic Retention Time, Sulfate Loading Rate, COD/SO42- Ratio

Document Type : Original Article

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Water Pollution Research Department, Environmental Research and Climatic Changes Institute, National Research Centre, P.O. Box 12622, El-Buhoth St., Dokki, Cairo, Egypt

Abstract

This paper introduces an application of biological treatment for industrial wastewater (IWW) contaminated with sulfate ions. Lab-scale up-flow anaerobic sludge blanket (UASB) bioreactor was fabricated for detecting the optimal operational conditions of sulfate ions removal with other impurities from IWW. Sulfate reducing bacteria (SRB) was effectively reduced sulfate into sulfide and let H2S gas liberated. The experiment has been carried out along 345 days of operational time. Results showed that, at pH 6.2, hydraulic retention time (HRT) between 24-18 h on increasing sulfate loading rate (SLR) up to 1.3 g SO42- L-1 d-1, the sulfate reduction efficiency (SRE) was increased from (53±11) up to (87±7) %, in addition to 99% heavy elements removal, respectively. However, on decreasing HRT to 12.0 h with increasing SLR up to 3.6 g SO42- L-1d-1, the sulfate reduction (SR) rate decreased to 66±3‌‌ %. On increasing the temperature from 25 to 35oC, the SRE was increased from 68 to 83%. When COD/SO42- ratio was increased from 2.0 to 5.0, the SRE was slightly decreased from 74±10 to 68±6%, respectively. Moreover, when COD/SO42- ratio was increased from 5.0 to 10.0, (SRE) decreased from 68±6 to 66±3%. Consequently, the optimal operational conditions of the UASB reactor for maximum SRB at temperature, HRT, SLR, and COD/SO42- ratio of 35oC, 18h, 1.3g SO42-L-1d-1, and 2.0, respectively, while Fe2+ is essential.

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History

  • Receive Date: 05 February 2023
  • Revise Date: 18 March 2023
  • Accept Date: 26 March 2023

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