Extreme removal of phosphorus from wastewater now possible

25 April 2013

In South Africa, nutrients in wastewater effluents are the cause of most of the eutrophication problems this country experiences.  While nitrogen removal from wastewater effluents is effective, phosphorus (P) attenuation is far less so, resulting in high loads of this element being dumped into our rivers and dams.  Most wastewater treatment plants have phosphorus concentrations measured in milligrams P per liter, while a few plants manage to attain, at best, around 500 micrograms P per liter (0.5 milligrams per liter).

In the USA, advanced wastewater treatment plants (AWTs) have for some time been able to consistently produce an effluent with a P concentration of 100 micrograms per liter (0.1 milligrams).  Now, further advances tested at a works in Spokane USA  have shown that half that again, i.e. 50 micrograms per liter, is possible using a process termed Chemically Enhanced Primary Treatment (CEPT).  This is a seriously “Wow!” moment and probably the single most important advance in wastewater treatment (from an environmental protection perspective) for many, many years!

Should the CEPT process be economically-viable then it could be singularly responsible for negating wastewater-caused eutrophication around the world.  It does not look cheap (see below) but economies of scale and essential, environmental-protection incentive subsidization, could be brought to bear.

The capital cost came in at US$172 million — US$143 million for the design-build and an additional US$29 million for conveyance infrastructure and ancillary costs — financed through ratepayers over a payback schedule of 20 to 25 years. The cost of not building the facility, however, could have been much more. Water quality is being restored to the Spokane River and Lake Spokane, some of the burden from the existing downstream plant has been temporarily lifted, and thousands of septic systems were taken out of service for good, which also helps protect the Spokane-Rathdrum aquifer.

 

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