Water Reuse is a Key Element in Responsible and Sustainable Development

In 1970, about the time I began my career, the population of the Southern California Coastal Community was about 11 million people[1].  Following William Mulholland’s model, facilities had been built to import water from places far away.  Facilities nearing completion would increase the total capacity for importing water to 3.7 million acre-feet per year (MAF/Y), or about 893 million gallons per day.  That capacity of 3.7 MAF/Y has never been full utilized; this year it looks as though utilization will be only 60 percent.  Yet the population of that same Coastal Community is now approaching 20 million people and demographers tell us that it will continue to increase.

Considering the requirements of the environment, the impacts of global warming and the realities of the competition for water throughout the southwestern United States, the prospects for more imported water are not good. Meanwhile, the four largest wastewater treatment plants in Southern California have an aggregate capacity of more than 1 MAF/Y, most of which is discharged to the Pacific Ocean.  A key element of responsible and sustainable development in southern California will be finding ways to recover this resource. More importantly, this scenario repeats itself across the U.S. and in much of the developed world.

Reuse of municipal wastewater is not a new idea.  Wastewater managers, long vexed by the necessity to discard a resource in which they have invested so much, have been advocates of reuse for some time.  However, for just as long, efforts to promote reuse have been frustrated by good principles turned into rigid rules and cultural aversion that cannot be easily overcome.

Beginning early in the 19th Century, shortly after we began to use water to transport personal waste out of households in our major cities, we learned that it is important to separate this wastewater from drinking water.  In fact, for the first five decades after John Snow’s demonstration of the connection between sewage contamination and waterborne disease, it was separation, not treatment, that was most important for public health protection.  So, we went long distances to obtain uncontaminated water supplies and relied on Thomas Hawksley’s ingenious idea of delivering the water in systems that were continuously pressurized to ensure the water remained uncontaminated. 

Treatment was always an alternative to finding “virgin” water, but it was generally reserved for contaminated water even after treatment became more sophisticated with the introduction of coagulation and filtration by George W. Fuller in the last decade of the 19th Century, and the introduction of chlorination by George Whipple at the inception of the 20th Century. Suppliers of drinking water continued to prefer protected supplies in lieu of treatment. In fact, many of these protected supplies received no treatment beyond disinfection until the last two decades of the 20th century when we discovered zoonotic pathogens like Giardia lamblia and Cryptosporidium.  Since these microbes can infect animals as well as humans, they show up in water supplies that have never been exposed to human waste.  

The time has come to re-examine our national practice.  The increase in the human population has now reached a density which requires we change our water lifestyle. The population in Southern California, for example, has already begun to make changes in lifestyle to conserve water.  So far, those changes have been relatively painless; tiered water rates (higher prices for those who use more water), low volume toilets, low flow shower heads, drip irrigation, etc.  Future changes, required as the population continues to increase, will be more noticeable.  Dramatic changes in landscaping are an example of changes some communities are already making.

Increases in population have also had a pervasive impact on the environment, making the idea of a truly protected supply seem unattainable.  These effects, combined with advances in analytical technology, result in our ability to find evidence of man-made chemicals in all but the most protected water supplies.  This was recently demonstrated in the survey of drugs in drinking water published by the Associated Press [2].  While it is difficult to identify a specific risk associated with these findings, they challenge the premise that water supplies can be taken from sources free of human influence and they put the choice between protected water and unprotected water with treatment squarely in the realm where we must compare one risk with another, absolute safety not being attainable.

Finally the past two decades have seen unprecedented advances in water treatment technology.  This is true with membrane processes in particular, but it is also true with respect to our understanding of oxidation (and advanced oxidation).  Most significantly, membrane technologies have made the elimination of the threat of microbial disease possible and, historically, the risk of microbial disease has been the most significant obstacle to reuse. 

Numerous reuse projects are now in place all over the world, including significant new projects in Orange County, CA and in Singapore.  Nevertheless, too many reuse proposals still fall victim to the familiar fears of contamination.  We are making headway in the arena of regulation and science, but as the architects of the water infrastructure for the new century, we need to find ways to garner the public’s support as well.

R. Rhodes Trussell, Issue Editor
Trussell Technologies, Inc.