Sewer Mining: Extreme Measure or Viable Solution?
6-Star Green Star-rated building, Council House 2 in Melbourne, Australia, pioneered an urban innovation, “sewer mining” of blackwater for treatment and reuse in buildings. Courtesy of the City of Melbourne.
A 9-story public office building, Council House Two (CH2) in Melbourne, Australia, implemented sewer mining with an in-house blackwater treatment system. Sewage extracted or “mined” from a sewer main located in the street near the building, along with wastewater produced in the building, is purified using a multi-water reuse (MRW) plant in the basement. The wastewater undergoes a micron-sized prescreening, ceramic ultra-filtration and finally reverse osmosis, which together purify it to a Grade-A drinking-water-quality standard.
The system processes more than 26,000 gallons of wastewater per day, and the effluent provides recycled wastewater for toilet flushing, a roof garden and other uses. The sewage treatment plant, coupled with a 5,280-gallon rainwater and fire-sprinkler-test water collection and storage tank onsite, supply 100 percent of CH2’s non-potable water.
There is plenty of water flowing in cities in the sanitary sewer system, so why not tap into it? Considering the increase in droughts, potential water supply shortages and the expense associated with transporting and treating water, sewer mining is an approach that could supplement current water supplies and help prevent a future urban water crisis. In fact, my engineering friends tell me that many new large office projects in Australia are incorporating sewer mining into their design as a viable approach to meeting water demands, especially from cooling tower make-up water.
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