Development of LEEO® technology for efficient H₂S control from saline wastewater sludge: From lab study to pilot trial

Sulfate-laden wastewater presents a challenge in controlling hydrogen sulfide during sludge treatment and disposal. Wastewater in areas such as Hong Kong SAR presents copious amounts of sulfate from seawater toilet flushing, reflecting high sulfate (100–150 mg-S/L) in the sewage sludge. To resolve this critical issue, a new electrochemical pretreatment process, Low Energy Electrical Odor control (LEEO®), was developed to suppress sulfide production in the sludge from lab studies to a pilot demonstration (~7 m³ sludge/day) at a local chemically enhanced primary treatment works. LEEO® simultaneously eliminated sulfide production for up to 5 days while having enhanced dewaterability of 20–30 % without chemical addition. The total energy consumption could be reduced to 0.20 kWh/kg total solids by optimizing the operation input for sludge sulfide control. Furthermore, the LEEO® pilot system demonstrated stability toward sulfide control under different weather (e.g., rainy and sunny) and temperature (23–38 °C) conditions, and confirmed the low comparative developmental toxic impact on the final effluent of the trialed treatment works. The successful upscaling from lab study to pilot demonstration laid the foundation for a full-scale demonstration development of LEEO® as an efficient and long-lasting sulfide control method for saline or sulfate-laden wastewater sludge.