提标升级对乡镇污水处理厂碳排放特征的影响

Impact of upgrading on carbon emission characteristics of township sewage treatment plants

  • 摘要: 在碳达峰、碳中和和流域水污染防治的背景下,乡镇污水处理厂减污降碳协同势在必行。基于成都市某乡镇市政污水处理厂2016—2022年水质水量数据,分析提标升级前后化学需氧量、氨氮、总磷、总氮的时间变异性,利用《IPCC 2006 国家温室气体清单指南》(2019年修订版)、《城镇水务系统碳核算与减排路径技术指南》评估直接、间接碳排放强度特征,探究提标升级前后碳排放量对季节、水质及污染物削减量的响应。结果表明:1)污水处理厂主体工艺从周期循环活性污泥法(CASS)升级为厌氧-缺氧-好氧-膜生物反应器法(AAO-MBR)后,出水水质满足DB 51/2311—2016《四川省岷江、沱江流域水污染物排放标准》,升级后通过增加碳源、利用MBR膜截留污泥等措施,使出水水质指标更加稳定,对污染物的处理效率更高;2)提标升级后,直接、间接碳排放强度分别为0.296和1.082 kg/m3(以CO2当量计),分别增加41.59%和105.70%,且夏季碳排放强度显著低于其他季节(P<0.01),升级前后的间接碳排放强度均高于直接碳排放强度;3)提标升级后,总碳排放强度增加了0.643 kg/m3(以CO2当量计),工艺升级导致的电耗增加,使得间接碳排放强度变化更显著。乡镇污水处理厂提标升级在提高处理效能的同时也增加了碳排放量,建议在工艺改造中协同考虑污染物去除与能耗控制,以实现减污降碳协同增效。

     

    Abstract: To achieve carbon peak and neutrality targets and control watershed water pollution, township sewage treatment plants (STPs) need to collaborate in reducing pollution and carbon emissions. Based on water quality and quantity data from 2016 to 2022 at a municipal sewage treatment plant in a township in Chengdu, the temporal variability of COD, NH3-N, TP, and TN was analyzed before and after the standard enhancement and upgrading. Using 2006 IPCC Guidelines for National Greenhouse Gas Inventories (2019 revision) and Guidelines for Carbon Accounting and Emission Reduction in the Urban Water Sector, the characteristics of direct and indirect carbon emission intensity were investigated, and the response of carbon emissions to seasons, water quality, and pollutant reduction amounts before and after the standard enhancement and upgrading was explored. The results showed: (1) After upgrading from Cyclic Activated Sludge System (CASS) to Anaerobic-Anoxic-Oxic -Membrane Bioreactor (AAO-MBR), the effluent quality met Emission Standards for Water Pollutants in Minjiang and Tuojiang River Basins of Sichuan Province (DB 51/2311-2016). Moreover, by increasing carbon source, using MBR membrane to trap sludge and other measures, the effluent concentration and water quality indexes were more stable, and the treatment efficiency of pollutants was higher. (2) After upgrading, direct and indirect carbon emission intensities increased by 41.59% and 105.70%, respectively, with values of 0.296 and 1.082 kg/m3 (in terms of CO2-eq). In summer, the carbon emission intensity was significantly lower than that of other seasons (P<0.01), and indirect carbon emission intensities before and after the upgrade remained higher than direct carbon emission intensity. (3) After the upgrade, the total carbon emission intensity increased by 0.643 kg/m3(in terms of CO2-eq). Due to increasing electricity consumption caused by upgrading, the indirect carbon emission intensity significantly changed. Therefore, the township STP upgrading could not only improve treatment efficiency but also increase carbon emissions. It was recommended to consider pollutant removal and energy consumption control synergistically during process transformation to achieve pollution reduction and carbon emission reduction simultaneously.

     

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