Clear understanding of mankind’s effect on the water cycle would bring about greater appreciation of the benefits of used water treatment and the extent of our dependence on carefully managed and regulated indirect potable reuse.
Pamela Wolfe, Managing Editor
One advantage of working with electronic and print media is the privilege of not having to wait two months to respond in only one media to reader enquiries. Just last week one well-informed reader’s quick response to my use of the phrase “direct use of recycled wastewater” in my introduction to the October WWI E-newsletter (October 12, 2006) was enlightening. The Enewsletter is sent monthly to WWI subscribers.
To explain the context, the article briefly reported answers to a question posed to four corporate and industry leaders during a roundtable discussion moderated by WWI that was conducted as part of the Aquatech Amsterdam 2006 Opening Session on September 25. Panelists included: ITT Fluid Technology President Hank Driessel; Vice President of GE Water & Process Technologies Jeff Connelly; International Water Association President Paul Reiter; and Siemens Water Technologies’ Chief Executive Officer Roger Radke.
One question I asked focused on the feasibility of recycling wastewater on a large scale for direct use as drinking water. Radke explained that it is technically possible to produce clean drinking water from sewage water, although public acceptance remains a challenge. The rest of the panel agreed. Advances made in the treatment of drinking water and wastewater now ensure the removal of harmful chemical and microbial contaminants.
Only one percent of water treated by public water systems is used for drinking and cooking, according to the UK Rainwater Harvesting Association, approximately 70 percent is used for irrigation, and the rest is used to meet the growing demand for industrial process water. Recycled wastewater applications in agriculture and industry, therefore, could help to conserve drinking water by replacing drinking water or water taken from drinking water sources.
Connelly emphasized that increasing the use of recycled wastewater for irrigation and industry worldwide would reduce the overall demand on available water supplies. The focus of major water technology companies reflect this trend; many industries in water-scarce regions are opting to recycle wastewater in order to produce their own reliable, clean industrial process water.
Bruce Durham, the technical secretary of the EUREAU Water Recycling and Reuse Working Group (www.eureau.org) responded:
“Interesting article, but why is there no discussion about indirect potable reuse? Direct reuse for potable is a viable option, but only if there is no choice. Direct potable reuse is not necessary as it is safer, easier and more efficient to indirectly reuse treated used water through our rivers, catchment reservoirs, and aquifers. So why do we keep writing articles referring to direct potable reuse? Direct reuse for irrigation or industry is of course a well established practice. The world's population in river basins relies on treated used water indirectly (with a level of freshwater dilution depending on the time of the year) to supply the freshwater source that is then treated to potable standards.
“Most people live downstream of someone else. The used water treatment plants or water reclamation plants are there to produce fresh water and recharge the water resource so that it is available for the environment and for licensed abstraction. The UWWTD (EC Urban Wastewater Treatment Directive) is not just there to treat a waste product for disposal while protecting the environment; it’s there to produce an essential freshwater resource as described in the UE Water Framework Directive.
“The big problem here is that everyone understands the natural water cycle, but not the real water cycle as it does not include people. Very few (people) know where their potable water comes from or where their used water goes. If there was a better understanding of the anthropogenic water cycle, there would be less confusion and a greater appreciation of the benefits of used water treatment and on how much we depend on carefully managed and regulated indirect potable reuse.”
An excellent point. Most people turn on the tap and never consider the substances that had to be removed from their drinking water source before clean, potable water flows from their faucet. If consumers realized the ways in which human activities affect the source of their drinking water, would they still dispose of their unused pharmaceuticals and paint thinners down the domestic sink? Or be complacent about toxic discharges to surface water and overuse of agricultural fertilizers? Remain critical of increases in taxes or water prices needed to upgrade outdated water and wastewater treatment plants?
Residents living in New Orleans, Louisiana, USA, drink treated water from the Mississippi River that winds its way slowly from Montana through Louisiana for 6,240 kilometers until it discharges into the Gulf of Mexico. Its watershed drains parts of 31 states and two Canadian provinces. Along the way, hundreds of communities, small and large, depend on the river for raw water and disposal of treated sewage, wastewater, and stormwater. Municipalities take raw water from the river, treat it to US Environmental Protection Agency (EPA) drinking water quality standards, and then ultimately discharge treated effluent back into the river. This is very similar to other major rivers such as the Rhine or the Thames.
In Louisiana, between Baton Rouge and New Orleans, industries release half of industrial discharges to surface water in the USA, according to the Mississippi River Basin Alliance. When does this used water become fresh water again? Readers are welcome to respond…
