The Latest Grist from the Mill:
WATER REUSE: COMING OUR WAY SOON?
Dan Hudson, 09/28/2007
Reading Rick Dunn’s June article on MBR’s (Membrane Bioreactors) made me pause and reflect on how quickly advances in technology keep changing the way we do things in our industry. MBR’s have been a hot topic these days, and it seems you can't open a trade magazine or view an industry website without hearing about them. As wastewater engineers, they provide us with a reliable and economical tool to produce high quality effluent.
Another hot item we hear about these days is Water Reuse, a fairly common term, but what exactly is it? And how will it affect us? Traditionally, wastewater has always been considered a problem, something to be treated so it could be simply gotten rid of, and the level of treatment required was determined by the method of disposal. Nationwide there is an increasing demand for water, and actual water shortages have been experienced in many parts of the country. With the recent advances in wastewater treatment technology, treated wastewater is increasingly being seen as a valuable commodity, and it is now possible to use treated wastewater where historically, only potable water was suitable or available.
There are several terms being thrown around when talking about wastewater reuse. While "wastewater reclamation" and "wastewater recycling" are also commonly used, the term "water reuse" is becoming more and more popular. The United States Environmental Protection Agency (US EPA) defines wastewater reuse as “using wastewater or reclaimed water from one application for another application” and categorizes types of water reuse as follows:
Urban Reuse: Irrigation of parks, school yards, and residential landscapes; fire protection; toilet flushing in commercial and industrial buildings; construction; and street cleaning
Agricultural Use: Irrigation of crops, including food crops, pasture lands, and nurseries (The level of required treatment is dependent on the type of crop to be irrigated)
Recreational Impoundments: Ponds and lakes
Environmental Reuse: Creating wetlands and enhancing existing wetlands and stream flows
Industrial Reuse: Various industrial uses, including cooling water
Groundwater Recharge: Of both potable and non-potable aquifers
For many years, water reuse has been employed in some areas of the country, and many states, including New Jersey, have developed regulations and standards governing the practice. In 1992, the US EPA published “Guidelines for Water Reuse”, which included a survey of how various states have implemented programs. In general, the states have established water quality limits for types or classes of reclaimed water, and have determined the required level of treatment for various uses. As might be expected, the level of required treatment depends on the anticipated use.
In some areas where water reuse is an established practice, there are dual water distribution systems, one for potable water, and the other for recycled water. Typically, the pipe for the recycled water is color-coded purple to prevent accidental connections to the wrong line. St. Petersburg, Florida boasts the oldest municipal dual distribution system in the country, which includes more than 260 miles of pipe serving more than 10,000 homes and businesses with water used for lawn irrigation and industrial cooling.
Water reuse projects have generally been implemented in areas of the country with little rainfall. However, recent droughts in Pennsylvania have prompted various agencies to investigate the potential for reuse, and the Pennsylvania Department of Environmental Protection (DEP) is in the process of developing guidelines. Progress, however, is impeded due to differing opinions between regional offices of the agency regarding the level of treatment that should be provided for a given use.
Although there is generally plenty of good, cheap, potable water available in Pennsylvania, unique circumstances can make water reuse an attractive alternative. At least one beneficial reuse project has been approved in Pennsylvania, and the initial phase of the project has been constructed and is now operating. The University Area Joint Authority (UAJA) operates the Spring Creek Pollution Control Facility which serves the Centre Region of Pennsylvania, a council of local governments that surrounds and includes the Borough of State College and the Pennsylvania State University. The facility discharges treated effluent to Spring Creek, a world famous trout stream. Faced with thermal discharge limits, coupled with the fact that projected increases in groundwater withdrawal would reduce the stream flow in the area and further exacerbate the problem, the UAJA elected to construct a water reuse system that produces a potable quality effluent. As part of the project, a water distribution system is being constructed and will ultimately include 11 miles of pipeline to distribute reclaimed wastewater to local area industrial users, including a cement plant, a commercial laundry, a concrete plant, and a golf course. The water will also be used to restore and enhance stream flow by discharging to constructed wetlands and groundwater aquifers. With Pennsylvania still in the process of developing water reuse standards, the authority designed the facility to produce a product that meets the nation’s most stringent discharge standards. In addition to the membrane systems described in Rick’s previous article, the facility uses Reverse Osmosis, a technology that is used to remove dissolved solids from the effluent.
The potential for water reuse should be kept in our engineers' “bag of tricks” with MBR’s and all the other new tools that technology has given us for treating wastewater. It is certain to be something we will see more of in the future.
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18 Nov 2013
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