Sludge management has a significant impact on operating costs in municipal wastewater treatment plants (WWTPs). The current trend is to optimize the sludge management in order to enhance the energy independence from external energy suppliers, while reducing the operating costs of the WWTP. One of the methods is through the pretreatment of waste activated sludge (WAS). In this work, low-temperature alkaline pretreatment of WAS was examined as a method of improving the economic balance of the WWTP. In the initial pretreatment tests, the impacts of NaOH dose, temperature and reaction time on COD release as well as the degree of sludge disintegration were examined. Semi-continuous anaerobic digestion (AD) trials were then performed for pretreated WAS in selected conditions with low NaOH dosage for which no pH adjustment was required (16 g of NaOH/kgTS of WAS, 60 °C, 60 min). The tests showed an increase in methane yield from 210.4 ± 10.9 mL CH₄/gVS to 248.8 ± 13.1 mL CH₄/gVS and 267.1 ± 14.3 mL CH₄/gVS for HRT 15 d and HRT 21.5 d, respectively. Energy balance and economic calculations for a full-scale WWTP were conducted based on the obtained results. It was concluded that it would be possible to increase electricity production from methane originated from AD of pretreated WAS up to 27% as well as to reduce the amount of dewatered sludge up to 8.7%. Energy balance and cost-benefit analyses indicated a possibility to reduce the operating cost by over 300,000 EUR/year in the case of a 1,200,000 people-equivalent WWTP.

污泥管理对市政污水处理厂 (WWTP) 的运营成本有重大影响。当前的趋势是优化污泥管理，以提高能源独立于外部能源供应商的能力，同时降低污水处理厂的运营成本。其中一种方法是对废弃活性污泥（WAS）进行预处理。在这项工作中，研究了 WAS 的低温碱预处理作为改善污水处理厂经济平衡的方法。在初始预处理试验中，考察了 NaOH 剂量、温度和反应时间对 COD 释放以及污泥分解程度的影响。然后在选定的条件下对预处理的 WAS 进行半连续厌氧消化 (AD) 试验，低 NaOH 剂量不需要调节 pH 值（16 g NaOH/kgTS WAS，60 °C，60 分钟）。测试表明，甲烷产量从 210.4 ± 10.9 mL CH对于 HRT 15 天和 HRT 21.5 天，₄ /gVS 分别为 248.8 ± 13.1 mL CH ₄ /gVS 和 267.1 ± 14.3 mL CH ₄ /gVS。基于获得的结果进行了全规模污水处理厂的能量平衡和经济计算。得出的结论是，可以将来自预处理 WAS 的 AD 的甲烷的发电量提高 27%，并将脱水污泥的量减少 8.7%。能源平衡和成本效益分析表明，在 1,200,000 人当量污水处理厂的情况下，有可能将运营成本降低 300,000 欧元/年以上。