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How might PUB recover phosphorus from dewatered sludge, dewatering centrate or sewage sludge incineration ash (SSIA) cost-effectively for safe and sustainable local vegetable production via hydroponics cultivation?
Challenge Owners
Phosphorus is a critical yet non-renewable resource for modern agriculture. Its current global reserves are expected to be depleted in 50 - 100 years. The phosphorus scarcity issue poses a serious threat to food security globally. Under the ’30 by 30’ goal, Singapore aspires to build up the capability and capacity of our agri-food industry to produce 30% of our nutritional needs sustainably by 2030. With limited land, Singapore has identified hydroponics as one Agri-tech that can help speed up the growing cycle of our homegrown tech without compromising on nutritional value.
Due to the potential depletion of phosphorus as well as more stringent regulations on the discharge quality to water courses, there is a growing interest worldwide to recover phosphorus from municipal wastewater treatment plants (WWTPs)1. PUB hence calls for a solution that can recover phosphorus from the following waste streams from our local water reclamation plants (WRPs) that are suitable for local agricultural use:
| Waste Streams | Quantity | Total Phosphorus (TP) Concentration |
|---|---|---|
| Dewatered Sludge | 300,000 tonnes/year | 5-11g/kg dry solid |
| Dewatering Centrate | 3,500,000 m3/year |
200 – 300 mg/L |
| Sewage Sludge Incineration Ash |
30,000 tonnes/year |
55-86 g/kg dry solid |
PUB had conducted several trials with SFA to investigate the applicability of phosphorus recovery from waste streams from WRP. The known limitations are as outlined below:
1For instance, Germany stipulates phosphorus recovery from WWTPs with at least 100,000 population equivalents (PE) mandatory by 2029.
PUB is interested in seeking partners to work with who can identify phosphorus recovery process that can be integrated with PUB’s used water treatment processes or paired with incineration plants to recover phosphorous from the various waste streams, such as dewatered sludge, dewatered centrate and SSIA.
The phosphorus product recovered must be of quality, free of contaminants and readily soluble in water so that it can be applied as part of nutrient solution for hydroponics cultivation. The overall cost-benefit analysis of the solution, and the consistency of the phosphorus produced across batches for hydroponics cultivation shall be demonstrated.
Considerations to be addressed include:
A prototype or equivalent that can effectively recover phosphorus from the waste stream(s) of PUB’s WRP in a form suitable for local agricultural use. Techno-economic analysis should also be included to illustrate the merits of the proposed solution.
If the preliminary study or proof-of-concept is successful, PUB may further scale up the solution.
Challenge Owners
Phosphorus is a critical yet non-renewable resource for modern agriculture. Its current global reserves are expected to be depleted in 50 - 100 years. The phosphorus scarcity issue poses a serious threat to food security globally. Under the ’30 by 30’ goal, Singapore aspires to build up the capability and capacity of our agri-food industry to produce 30% of our nutritional needs sustainably by 2030. With limited land, Singapore has identified hydroponics as one Agri-tech that can help speed up the growing cycle of our homegrown tech without compromising on nutritional value.
Due to the potential depletion of phosphorus as well as more stringent regulations on the discharge quality to water courses, there is a growing interest worldwide to recover phosphorus from municipal wastewater treatment plants (WWTPs)1. PUB hence calls for a solution that can recover phosphorus from the following waste streams from our local water reclamation plants (WRPs) that are suitable for local agricultural use:
| Waste Streams | Quantity | Total Phosphorus (TP) Concentration |
|---|---|---|
| Dewatered Sludge | 300,000 tonnes/year | 5-11g/kg dry solid |
| Dewatering Centrate | 3,500,000 m3/year |
200 – 300 mg/L |
| Sewage Sludge Incineration Ash |
30,000 tonnes/year |
55-86 g/kg dry solid |
PUB had conducted several trials with SFA to investigate the applicability of phosphorus recovery from waste streams from WRP. The known limitations are as outlined below:
1For instance, Germany stipulates phosphorus recovery from WWTPs with at least 100,000 population equivalents (PE) mandatory by 2029.
PUB is interested in seeking partners to work with who can identify phosphorus recovery process that can be integrated with PUB’s used water treatment processes or paired with incineration plants to recover phosphorous from the various waste streams, such as dewatered sludge, dewatered centrate and SSIA.
The phosphorus product recovered must be of quality, free of contaminants and readily soluble in water so that it can be applied as part of nutrient solution for hydroponics cultivation. The overall cost-benefit analysis of the solution, and the consistency of the phosphorus produced across batches for hydroponics cultivation shall be demonstrated.
Considerations to be addressed include:
A prototype or equivalent that can effectively recover phosphorus from the waste stream(s) of PUB’s WRP in a form suitable for local agricultural use. Techno-economic analysis should also be included to illustrate the merits of the proposed solution.
If the preliminary study or proof-of-concept is successful, PUB may further scale up the solution.
