Effects of Cr³⁺ and Ni²⁺ on the efficiency and performance of sequencing batch reactor (SBR) system

Abstract

Sequencing batch reactor (SBR) system at hydraulic retention time (HRT) of 1.5 days could be used for the treatment of Ladkrabang industrial estate wastewater (LIWW) with high Cr³⁺ and Ni²⁺ removal efficiencies of 80.7 ± 17.9 and 53.5 ± 25.1%, respectively. Bio-sludge of SBR system with synthetic industrial estate wastewater (SIWW) showed the highest Cr³⁺ and Ni²⁺ adsorption yields of 36.00 ± 9.80 and 31.59 ± 9.67 mg/g, respectively but they were reduced to 25.20 ± 8.38 and 20.49 ± 7.20 mg/g, respectively with LIWW. Cr³⁺ and Ni²⁺ strongly suppressed the growth and activity of heterotrophic bacteria. Ni²⁺ at 3.0 mg/L did not impact either nitrifying or denitrifying bacteria, while the growth and activity of denitrifying bacteria was suppressed at 3.0 mg/L Cr³⁺. The other advantage of SBR system was that the bio-sludge could adsorb inorganic matters from LIWWs, which contains high inorganic content about 33%.

Key words: Adsorption, chromium, heavy metals, nickel, sequencing batch reactor (SBR) system.