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Summary
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Two novel phosphorus recovery processes, which effectively enable the reuse of recovered phosphorus as a resource, have been developed. These processes have been designed with full consideration given on the specific characteristics (sewage components, chemical concentrations, flow rates, etc.) of wastewater or sludge generated from sewage treatment. The first of these processes, named Rephosmaster CS, features the treatment of wastewater with high concentrations of suspended solids, such as that containing anaerobic digested sludge. The other, named Rephosmaster FB, is for the same with low concentrations of suspended solids, such as filtrate from dewatering machines and recycle flow. These processes have been proven effective for not only recovering phosphorus as a resource, but also for the prevention of eutrophication which may result from residual nitrogen and phosphorous in the effluent.
Rephosmaster CS recovers struvite from anaerobic digested sludge in wastewater. Demonstration and Verification tests using a full-scale plant and pilot-scale plant were as the following.
(i) Full-scale demonstration of using a 239 m3/d facility installed in Higashinada MWTP since 2013
(ii) Pilot-scale verification tests using a 6m3/d facility installed in WWTP in 2011
(iii) Full-scale verification tests using a 50m3/d facility installed in WWTP in 2007
(iv) Pilot-scale verification tests using a 6m3/d facility installed in WWTP in 2005
Resphosmaster CS process comprises trash removal equipment, a CSTR and a Struvite Separator. The viscosity of the digested sludge, containing several percentage of suspended solids, is higher than the viscosity of wastewater or sewage. To cope with this, a CSTR is used as the crystallization reactor to enable maximum seed crystal growth in the liquid. Almost all results of demonstration and verification tests indicated that PO4-P recovery rates were exceeding 90%. Moreover, the amount of hazardous metals in the recovered struvite was below the standard regulatory levels specified in the Fertilizer Regulation Act , Ministry of Agriculture of Japan. This established that struvite particles recovered by the process were suitable for use as a fertilizer.
In contrast, Rephosmaster (TM) recovers struvite from filtrate in sewage wastewater treatment plants and night soil treatment plants. The verification tests conducted for this process were as the following.
(i) Full-scale plant in a 48m3/d facility designed for night soil treatment plant, constructed in 2014
(ii) Pilot-scale verification tests using a 7.2m3/d facility installed in a night soil treatment plant in 2011
(iii) Pilot-scale verification tests in a 20m3/d facility installed at WWTP in 2003
The process comprises a fluidized bed struvite reactor equipped with a seeder. The reactor system includes a fluidized bed reactor, capable of treating more than 80% of the raw water, and a seeder, which produces seed struvite to be used in the fluidized bed reactor. All results of verification tests indicated an orthophosphate recovery exceeding 90 %, as was the case of Rephosmaster (TM) CS.
Reference: European Sustainable Phosphorus Platform, SCOPE NEWSLETTER, No. 104, pp18-19 (2014)
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Technology Benefits
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Rephosmaster (TM) CS, features the treatment of wastewater with high concentrations of suspended solids, such as that containing anaerobic digested sludge. The other, named Rephosmaster FB, is for the same with low concentrations of suspended solids, such as filtrate from dewatering machines and recycle flow. These processes have been proven effective for not only recovering phosphorus as a resource, but also for the prevention of eutrophication which may result from residual nitrogen and phosphorous in the effluent.
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