Innovative Integrated Reactor System for Carbon, Sulfur and Nitrogen Removal Based on Biological Phase-Separation

Abstract

An innovative biological wastewater treatment system for the removal of organic carbon, sulfur and nitrogen was developed based on biological phase-separation principle. This system consists of three reactors integrated together i.e. sulfate reduction and organic matter removal (SR-CR), autotrophic and heterotrophic denitrifying sulfide removal (A&H-DSR) and nitrification (AN) reactors. In this system, the operational parameters for successful bio-phase separation are sulfate and organic loading rate, hydraulic retention time (HRT), COD/SO42-ratio and pH for the SR-CR reactor, and sulfide and nitrate loading rate, HRT, pH, S2-/NO3-ratio and COD/NO3-for the A&H-DSR reactor. The results from a laboratory scale system demonstrated that for the SR-CR reactor, the optimal operating conditions were HRT≥24 h; sulfate and organic loading rate ≤7.5 kg SO42-/m3•d and ≤10 kgCOD/m3•d; COD/SO42-≥2; and pH ≥6.5. For A&H-DSR process, the optimal conditions are sulfide loading rate ≤6.0kg S2-/m3•d; nitrate loading rate ≤3.5 kg NO3-/m3•d; S2-/NO3-≥1; COD/NO3-≥1.25:1; and pH≥7.5. Under such conditions, high sulfate, ammonia and organic matter removal of 99%, 90% and 99% were achieved, respectively. In this case, the elemental sulfur (S0) reclamation efficiency reached 6.0 kg S0/m3•d, around 20 times higher than the maximum level as referred in the literatures. DGGE profiling indicated that the predominant functional organisms of Clostridiaceae sp., Desulfomicrobium sp., Methanosaeta sp. dominated in the SR-CR reactor, and Sulfurovum sp., Pseudomonas aeruginosa and Denitratisoma sp. in the A&H-DSR reactor. These species played essential role in metabolic functions in each bio-phase.