Waste Not, Want Not — Turning Wastewater Into An Asset
By Bryan Webb
Every water project is different, but each one also provides lessons for others, such as this profile of a Southern California reuse project where conveyance needed to be routed around a protected environment.
In this age of repeated drought and water shortages, the line between water and wastewater is getting blurred. In parts of the U.S., such as California, drought conditions can last for years on end, and water and environmental engineers need to be creative when it comes to supplying water to meet every anticipated need.
One of the most important strategies revolves around taking the effluent from wastewater treatment and making it reusable as non-potable water. The treated water becomes a valuable asset that can be sold to farms, golf courses, and other industries that need water for irrigation.
The opportunities are obvious. In areas that suffer from frequent water shortages, having the ability to reuse wastewater offers extraordinary environmental and industrial benefits, not to mention the financial benefits to cities that are able to sell their wastewater.
Of course, any opportunity brings challenges. The challenges presented here are typical of those facing any wastewater treatment. The pumps and treatment facilities need to be able to handle the volume of wastewater created by the system. Also, in order to assure that there’s no exfiltration or infiltration, it may be necessary to put in new pipelines to assure that salt and brackish water won’t make their way into the treated water before it makes its way to buyers.
Environmental challenges are prevalent, particularly in areas with stringent environmental regulations. It’s essential to ensure that the system won’t impact the natural environments through which pipelines run or those that are adjacent to the treatment system.
A Case In Point
One seaside community in Southern California is in the process of creating a wastewater treatment facility for water reuse. A large development is underway that will eventually house up to 4,000 people, and of course, a development this large will create a lot of wastewater.
The city has traditionally sent its wastewater to an adjacent city for treatment. Through this project, a recycled water plant is being developed to permit the direct treatment and resale of the city’s wastewater. The new system will also feature an upgraded pipeline to handle the increased volume of wastewater and the resultant increase in water pressure.
In addition to the upgraded pipes, the system also includes a series of pump stations fed by both gravity and pressurized pipe. The pumping stations upgraded the existing pumping system while providing additional resources for moving the wastewater throughout the three-mile-long system.
Odor control was also an important consideration, and the system utilized a calcium nitrate-based system using Bioxide to control odors. The 4,400-gallon Bioxide storage tank features a double wall for spill containment and includes a number of overflow and pressurization features to assure that the containment tank won’t impact the local environment in any way.
The most significant challenge was assuring that the pipeline wouldn’t impact the environment. This was particularly important because the wastewater treatment plant is adjacent to a national wildlife reserve that serves as a critical habitat for dozens of species. A spill could have serious environmental repercussions.
Project engineers could have safely run the pipe system underneath the wildlife reserve without causing any environmental concerns. However, local officials were concerned that by doing so, they would be setting a precedent that would lead to similar installations of oil, natural gas pipes, or other types of infrastructure that could harm the local environment, particularly the wildlife reserve. Additionally, running the pipes under the wildlife reserve could have triggered regulatory issues that would cause significant delays. The entire project only had a six-month design frame, so it was important to avoid any unnecessary delays.
The solution was found by running the pipeline around the reserve with the aid of an old abandoned railway easement to keep the wastewater moving from the new development to the treatment center, while skirting the wildlife reserve. The upgraded pipes and pumps will assure that the system will be able to handle the increased volume of wastewater without impacting the local environment. After the water is treated, it can be sold to local businesses for industrial or agricultural uses.
From Wastewater To Liquid Gold
Drought is becoming increasingly common as weather patterns are altered through climate change. While California is the most obvious example, much of the rest of the western U.S. is also susceptible to drought. The good news is that some of this shortage can be offset through treatment strategies that convert wastewater to useful non-potable water. As the above example demonstrates, while there are challenges to be overcome, communities can improve existing wastewater treatment systems to turn their wastewater into liquid gold.
About The Author
Bryan Webb is a water engineer with Kleinfelder with an expertise in water and wastewater design and construction. He was the project engineer for the City of San Diego Water Master Plan, and he has also designed a number of utility pipelines and utility rehabilitation projects. He also has experience serving as a resident engineer for sewer and force main construction projects. He can be reached at BWebb@kleinfelder.com.