Effect of influent COD/N ratio on biological nitrogen removal (BNR) from high-strength ammonium industrial wastewater

The effect of influent COD/N ratio on biological nitrogen removal (BNR) from high-strength ammonium industrial wastewater was investigated. Experiments were conducted in a modified Ludzack–Ettinger pilot-plant configuration for 365 days. Total nitrification of an influent concentration of 1200 mg NH₄⁺–N l⁻¹ was obtained in this period. Influent COD/N ratios between 0.71 and 3.4 g COD g N⁻¹ were tested by varying the nitrogen loading rate (NLR) supplied to the pilot plant. An exponential decrease of nitrification rate was observed when the influent COD/N ratio increased.

The experimental COD/N ratio for denitrification was 7.1±0.8 g COD g N⁻¹ while the stoichiometric ratio was 4.2 g COD g N⁻¹. This difference is attributable to the oxidation of organic matter in the anoxic reactor with the oxygen of the internal recycle. The influence of influent COD/N ratio on the treatment of high-strength ammonium industrial wastewater can be quantified with these results. The influence of COD/N ratio should be one of the main parameters in the design of biological nitrogen removal processes in industrial wastewater treatment.     

Microbial treatment of high-strength perchlorate wastewater

To treat wastewater containing high concentrations of perchlorate, a perchlorate reducing-bacterial consortium was obtained by enrichment culture grown on high-strength perchlorate (1200 mg L⁻¹) feed medium, and was characterized in a sequence batch reactor (SBR) over a long-time operation. The consortium removed perchlorate in the SBR with high reduction rates (35-90 mg L⁻¹ h⁻¹) and stable removal efficiency over 200-day operations. The maximum specific perchlorate reduction rate (q_max), half saturation constant (K_s), and optimal pH range were 0.67 mg-perchlorate mg-dry cell weight⁻¹ h⁻¹, 193.8 mg-perchlorate L⁻¹, and pH 7-9, respectively. The perchlorate reduction yield was 0.48 mol-perchlorate mol-acetate⁻¹. A clone library prepared using the amplicons of cld gene encoding chlorate dismutase showed that the dominant (per)chlorate reducing bacteria in the consortium were Dechlorosoma sp. (53%), Ideonella sp. (28%), and Dechloromonas sp. (19%).     

Treatment of high-strength ammonium wastewater by polyvinyl alcohol–sodium alginate immobilization of activated sludge

We employed microorganism embedding immobilization technology to treat high-strength ammonium(NH₄⁺-N) wastewater. Experiments were conducted in batch reactors with different initial ammonium concentrations (50–400 mg/L), 10% particle dosage rates, 7.5–8.5 pH, and 495-min operation cycle. Stable treatment efficiency was reached in the 28th, 40th, 55th, 58th, and 58th cycles with average ammonium removal rates of 100, 100, 80.9, 64.6, and 48.0%, respectively. The ammonium removal reaction followed zero-order reaction kinetics. Brunauer-Emmett-Teller (BET) and Scanning Electron Microscopy (SEM) demonstrated that the specific surface area and pore size of beads in stable phase were larger than corresponding values for the unused embedding beads, and microorganisms were found in the interior and external surface of beads. High-throughput sequencing illustrated that the microbial community composition significantly differed between the interior and external surface of embedding beads. And the existence of heterotrophic nitrifying and aerobic denitrifying bacteria may provide additional pathways for biological nitrogen removal in the reactors.