Electroflotation clarifier to enhance nitrogen removal in a two-stage alternating aeration bioreactor

• Published in: Environmental technology Vol. 34; no. 19; pp. 2765 - 2772
• Main Authors: Cho, Kangwoo, Chung, Chong Min, Kim, Yun Jung, Hoffmann, Michael R, Chung, Tai Hak
• Format: Journal Article
• Language: English
• Published: Abingdon Taylor & Francis 01-10-2013; Taylor & Francis Ltd
• Subjects: activated sludge; Aeration; alternating aeration bioreactor; Applied sciences; Biological and medical sciences; Bioreactors; Bioreactors - microbiology; Biotechnology; carbon nitrogen ratio; Chemical engineering; chemical oxygen demand; Clarifiers; Crack opening displacement; Electrochemical Techniques - instrumentation; Electroflotation; environmental technology; Equipment Design; Exact sciences and technology; Fundamental and applied biological sciences. Psychology; General purification processes; Influents; Methods. Procedures. Technologies; nitrogen; Nitrogen - isolation & purification; Nitrogen removal; Others; Pollution; Reactors; Sewage - analysis; Sewage - microbiology; Sewerage works: sewers, sewage treatment plants, outfalls; Tin; Various methods and equipments; wastewater treatment; Wastewaters; Water Purification - instrumentation; Water treatment and pollution; British Isles; Activated sludge; Water treatment; Stability; wastewater treatment; Nitrogen; Electroflotation; Retention time; Sewage treatment plant; Biological purification; alternating aeration bioreactor; nitrogen removal; Aeration; Pollutant; Bioreactor; Loading; Chemical oxygen demand; Water quality; Gas solid; Waste water purification
• ISSN: 1479-487X; 0959-3330; 1479-487X
• DOI: 10.1080/09593330.2013.788072

Stringent water treatment criteria and rapidly growing pollutant loads provoke the demand for retrofitting wastewater treatment plants towards a higher capacity. In this study, we assess a two stage alternating aeration (AA) bioreactor equipped with electroflotation (EF) clarifier, for nitrogen removal within a short hydraulic reTENTion time (HRT). The EF under steady solids loading required a minimum unit height and gas:solids ratio of 0.006 for efficient clarification. The separated sludge blanket was further thickened with retaining stability when the cyclic solids loading was smaller than 1.0 kg m ⁻². In the continuous operation of the bioreactor, the returned activated sludge concentration increased to more than 18,000 mg L ⁻¹, while the effluent suspended solids concentration was lowered below 5 mg L ⁻¹. Under influent chemical oxygen demand (COD)/total inorganic nitrogen (TIN) concentration of 300/30 mg L ⁻¹, the TIN removal efficiency was near 70% with cycle time ratios of 0.17 and 0.27. Under higher influent COD concentration of 500 mg L ⁻¹, TIN removal efficiency was found to be 73.4% at a carbon:nitrogen (C:N) ratio of 10 and even higher (80.4%) at a C:N ratio of 16.6. The increased mixed liquor suspended solids concentrations (>6000 mg L ⁻¹) under the high COD loading were efficiently maintained by using the EF clarifier. The results of this study demonstrate that an EF clarifier with a HRT of less than 1 h can support reliable nitrogen removal in the AA process that has a HRT of 6 h, even under increasing influent loadings.