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<p>Phosphorus removal technologies, such as chemical precipitation with alum or ferric chloride, effectively reduce phosphorus levels in wastewater. However, they produce large volumes of phosphorus-rich sludge, creating disposal challenges and leading to the loss of phosphorus—a critical and limited nutrient for agriculture. This study focuses on using a controlled composting process as an alternative phosphorus recovery and sludge management strategy for chemically precipitated sludge from wastewater lagoons. Composting experiments were conducted on alum sludge and ferric sludge recovered from a phosphorus removal system in a controlled temperature chamber. A 3:1 woodchip-to-sludge ratio, determined through preliminary trials, was used. Physicochemical properties, including moisture content, pH, and nutrient composition, were monitored throughout the 55-day composting process, followed by a 40-day maturation period. The final compost products were analyzed for organic matter, C:N ratio, and other key characteristics, with results compared to guidelines set by the Canadian Council of Ministers of the Environment (CCME) Class A compost. Both compost piles maintained thermophilic temperatures above 55&#xa0;°C for over 15&#xa0;days, facilitating effective pathogen reduction and decomposition. The final compost products met the CCME Class A standards, with C:N ratios of 12:1 (alum) and 17:1 (ferric), organic matter content exceeding 68% for both products, total organic carbon within 30–40% range, and moisture content of below 60%. These results suggest that a composting process can stabilize sludge and may be used as a strategy to recover nutrients including phosphorus from chemically precipitated sludge.</p>

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Composting of chemically precipitated sludge as a strategy for sludge stabilization and phosphorus reuse

  • 期刊论文

  • 发表日期：

    2025年7月5日

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  • Saba Vahedi,
  • Arman Vahedi,
  • Qiuyan Yuan

摘要

Phosphorus removal technologies, such as chemical precipitation with alum or ferric chloride, effectively reduce phosphorus levels in wastewater. However, they produce large volumes of phosphorus-rich sludge, creating disposal challenges and leading to the loss of phosphorus—a critical and limited nutrient for agriculture. This study focuses on using a controlled composting process as an alternative phosphorus recovery and sludge management strategy for chemically precipitated sludge from wastewater lagoons. Composting experiments were conducted on alum sludge and ferric sludge recovered from a phosphorus removal system in a controlled temperature chamber. A 3:1 woodchip-to-sludge ratio, determined through preliminary trials, was used. Physicochemical properties, including moisture content, pH, and nutrient composition, were monitored throughout the 55-day composting process, followed by a 40-day maturation period. The final compost products were analyzed for organic matter, C:N ratio, and other key characteristics, with results compared to guidelines set by the Canadian Council of Ministers of the Environment (CCME) Class A compost. Both compost piles maintained thermophilic temperatures above 55 °C for over 15 days, facilitating effective pathogen reduction and decomposition. The final compost products met the CCME Class A standards, with C:N ratios of 12:1 (alum) and 17:1 (ferric), organic matter content exceeding 68% for both products, total organic carbon within 30–40% range, and moisture content of below 60%. These results suggest that a composting process can stabilize sludge and may be used as a strategy to recover nutrients including phosphorus from chemically precipitated sludge.