Aerobic/semi-aerobic single-stage autotrophic nitrogen removal process for wastewater with high ammonia nitrogen levels (average ammonia nitrogen removal rate of 94%)

Thread Content

Application Scope: Wastewater with high ammonia nitrogen levels and low C/N ratios, such as landfill leachate, sludge effluent from wastewater treatment plants, and wastewater from livestock and poultry manure. Basic Principle: This technology utilizes restricted oxygen supply and a special reactor design to enable the initiation of an autotrophic nitrogen removal process within the same reactor in a short period of time, building on the sub-nitrous acid stage. It solves the problem related to the source of inoculum for single-stage autotrophic nitrogen removal reactors; moreover, its startup method is simple and easy, reducing the difficulty of starting up the system and shortening the startup time. Process flow: First, sludge is inoculated into a single-stage autotrophic denitrifying biofilm batch reactor ； Under conditions of limited oxygen supply and a small amount of organic carbon source, a microbial system dominated by nitrosifying and nitrifying bacteria was established ； By restricting oxygen supply, ammonia nitrogen is oxidized to the nitrous acid stage, thereby enriching nitrosifying bacteria and suppressing the growth of nitrifying bacteria, thus establishing a microbial system dominated by nitrosifying bacteria ； Based on a stable sub-ao acid phase, by adjusting the aeration method and controlling the dissolved oxygen level, the microenvironment in the reactor where nitrosifying bacteria and anaerobic ammonium oxidizing bacteria coexist is modified and optimized, thereby promoting the growth and accumulation of anaerobic ammonium oxidizing bacteria and enabling the operation of a single-stage autotrophic nitrogen removal system. Key technical aspects or design features involve initiating a single-stage autotrophic denitrification reactor on the basis of achieving the sub-anoic acid stage, in order to treat wastewater with high ammonia nitrogen levels and low C/N ratios, such as leachate from landfills, sludge effluents from sewage treatment plants, and animal waste from poultry farms. Promotion status: The sewage treatment plant of Bai Shi Yi Duck Food Co., Ltd. has a capacity of 1,200 t/a. Typical Case (I) Project Overview: The wastewater treatment plant project of Chongqing Baishiyi Duck Food Co., Ltd. is located at the company’s premises in Baishiyi, Chongqing, with a treatment capacity of 1200 tons per year. Construction began in June 2011, and it was completed in mid-September; since then it has been officially put into operation and is still in use today. It mainly deals with wastewater from the manure of pigs, ducks, chickens and other livestock and poultry that is temporarily stored, as well as wastewater generated during their slaughtering and processing. (II) Technical indicators: According to the acceptance report issued by the Chongqing Water Special Project Office, this process system achieves an average removal rate of 96% for COD, 94% for ammonia nitrogen, and 86% for TN. The quality of the treated wastewater meets the first-class standards set in the \"Emission Standards for Water Pollutants in the Meat Processing Industry\". This wastewater treatment facility reduces total nitrogen emissions by 0.14 tons per year, total phosphorus emissions by 0.05 tons per year, and COD emissions by 2.5 tons per year. It is also possible to recover ≥1.0 m3 of biogas per day/(m3·d) ； The COD removal rate for livestock and poultry farming waste is ≥75%. (III) Investment costs: For this project, the process technology is fully implemented through equipment, with no civil construction required; the total investment amounts to over 550,000 yuan. The investment cost per ton of water is 0.98 million yuan. The service life of the main equipment is over 15 years. (IV) Operating costs: This process integrates methane production via denitrification with autotrophic nitrogen removal, enabling the simultaneous removal of COD, nitrite, and ammonia nitrogen in wastewater. It allows for a 40% reduction in carbon sources, a 25% reduction in oxygen requirements, and a 300% decrease in sludge production. Based on data from over three years of operation, it shows that 1,200 tons of wastewater are processed per year, with annual operating costs amounting to 0.55 million yuan; the cost per ton of water processed is 4.6 yuan.