The future of wastewater treatment
Although the original goal of wastewater treatment was to protect water quality, today scarcity of resources and sustainability are driving major global changes. The N-E-W paradigm focuses on recovering resources such as Nutrients, Energy and Water.
The concept of discharging or disposing is gone as is describing constituents in wastewater as pollutants or contaminants. Beneficial use and resource recovery are the focus of using Water Resource Recovery Facilities (WRRFs).
For decades GHD has designed facilities for water reclamation and high performance capture of phosphorus and nitrogen. According to Alan B. Cooper, GHD's Head of Biosolids Technology in the USA, "Biosolids treatment consolidates nutrients into new products for beneficial uses such as soil amendments, compost, fertilisers, artificial soils, fuel and biochar as examples. Separate phosphorus recovery can also be done. Anaerobically digesting biosolids generates digester gas (60 percent methane) for co-generating electricity and heat, providing half of a WRRF's energy requirements assuming proper energy conservation. Digester gas can be refined to natural gas quality and even converted to liquid natural gas or LNG.
"Importation of high strength waste, food wastes and Fats/ Oils/Grease (FOG) into co-digestion can produce the methane required to produce as much energy as the WRRF requires. Examples include the Hill Canyon Treatment Plant in Thousand Oaks, California, which has been energy neutral since 2013 by receiving and treating FOG and wastes from dairies, a coffee plant and a brewery. Food wastes can be gathered efficiently from institutions, universities, schools, cafeterias, or restaurants.
"In addition, DC Water in Washington, DC, USA and Queensland Urban Utilities in Australia utilise hydrolysed anaerobic digestion for high levels of biosolids decomposition and digester gas production for power generation and heat."
Validating the benefits of biosolids technology, DC Water's Biosolids Program has been recognised by the Water Environment Research Foundation as 'one of the greenest projects in the world'. This has been achieved by improving all biosolids facilities and adding thermal hydrolysis, anaerobic digestion, and gas turbines to reduce biosolids by 50 percent, produce 13 MW of electricity and provide for all process heat. In this process, all biosolids are beneficially used.
Alan says, "As urbanisation increases demand on water resources, there are rising opportunities for wastewater treatment plants to become resource recovery plants."