A simple technology for phosphate (Pi) recovery has been developed using a bifunctional adsorption–aggregation agent. The bifunctional agent was prepared by soaking calcium silicates in hydrochloric acid solution. Importantly, recyclable calcium silicates were available almost free of charge from the cement industry and also from the steel industry. The acid treatment was essential not only for enhancing the ability of calcium silicates to remove Pi from aqueous solution but also for enabling the high settleability of removed Pi. On-site experiments using a mobile plant showed that approximately 80% Pi could be recovered from anaerobic sludge digestion liquor at a wastewater treatment plant. This technology has the potential to offer a simple, compact service for recycling Pi from wastewater to farmland in rural areas.
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