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In conventional secondary wastewater treatment, aeration step consumes much electricity resulting in higher energy cost and carbon dioxide (CO2) emission. Anaerobic digestion (AD) is recently used as an alternative treatment approach to reduce energy consumption and CO2 emission. Additionally, methane (CH4) produced in AD can be further used for electricity generation to lower the energy cost. To increase the efficiency of AD, forward osmosis (FO) pretreatment can be conducted to effectively concentrate the organic content such as chemical oxygen demand (COD) in wastewater under a relatively low-pressure system. A significant portion of water (> 60%) can be extracted from wastewater through semi-permeable FO membranes by using simple FO draw solution (i.e., 1 M sodium chloride (NaCl) or seawater). Thus, a higher COD content can be obtained for the AD process resulting in higher treatment efficiency. Hong Kong, a city located at coastal area uses seawater for toilet flushing to reduce freshwater consumption. Therefore, 4–5 ‰ salinity would be found in sewage. In this study, treatments of the sewage and synthetic domestic wastewater (SDW) (as a control) added with 4–5 ‰ NaCl were investigated by using an integrated FO-AD approach. Two small FO membrane units (i.e., 3 cm × 7 cm) applied with a 180–200 mL/min flowrate showed 6 L per m2 hour (LMH) water flux that significantly pre-concentrated the COD content in the sewage or SDW (i.e. 2–4 folds). Moreover, the effects of salinity and ratio of COD to AD sludge required for higher COD removal and methane generation were critically investigated. Preliminary results showed that >60% of concentrated COD content was effectively removed, and >30% methane was produced after 10 days of AD treatment in the presence of high salinity (~20 ‰). The parameters of FO (i.e. draw solution concentration, flowrate) and AD (i.e., pH, temperature) will be further optimized for better COD removal and methane generation assisting in the development of economically and environmentally sustainable wastewater treatment.

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Study on an Economical Wastewater Treatment Design for Achieving Environmental Sustainability Using Integrated Forward Osmosis-Anaerobic Digestion

  • 会议论文

  • 发表日期：

    2026年

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  • Wai-Yu Vivian Lam,
  • Shui-Shing Chan,
  • Cho-Yin Chan

摘要

In conventional secondary wastewater treatment, aeration step consumes much electricity resulting in higher energy cost and carbon dioxide (CO2) emission. Anaerobic digestion (AD) is recently used as an alternative treatment approach to reduce energy consumption and CO2 emission. Additionally, methane (CH4) produced in AD can be further used for electricity generation to lower the energy cost. To increase the efficiency of AD, forward osmosis (FO) pretreatment can be conducted to effectively concentrate the organic content such as chemical oxygen demand (COD) in wastewater under a relatively low-pressure system. A significant portion of water (> 60%) can be extracted from wastewater through semi-permeable FO membranes by using simple FO draw solution (i.e., 1 M sodium chloride (NaCl) or seawater). Thus, a higher COD content can be obtained for the AD process resulting in higher treatment efficiency. Hong Kong, a city located at coastal area uses seawater for toilet flushing to reduce freshwater consumption. Therefore, 4–5 ‰ salinity would be found in sewage. In this study, treatments of the sewage and synthetic domestic wastewater (SDW) (as a control) added with 4–5 ‰ NaCl were investigated by using an integrated FO-AD approach. Two small FO membrane units (i.e., 3 cm × 7 cm) applied with a 180–200 mL/min flowrate showed 6 L per m2 hour (LMH) water flux that significantly pre-concentrated the COD content in the sewage or SDW (i.e. 2–4 folds). Moreover, the effects of salinity and ratio of COD to AD sludge required for higher COD removal and methane generation were critically investigated. Preliminary results showed that >60% of concentrated COD content was effectively removed, and >30% methane was produced after 10 days of AD treatment in the presence of high salinity (~20 ‰). The parameters of FO (i.e. draw solution concentration, flowrate) and AD (i.e., pH, temperature) will be further optimized for better COD removal and methane generation assisting in the development of economically and environmentally sustainable wastewater treatment.