Reuse Wastewater Applications

Water recycling, also referred to as water reclamation and reuse, dates back approximately 3,000 years when the Mioan Civilization in Crete, Greece used wastewater for agricultural irrigation. In the United States, the first reference to wastewater reuse that considered health effects was in the Monthly Bulletin, California State Board of Health, in February, 1906, where the Oxnard septic system
effluent was discussed as a valuable, cost effective and safe source of fertilizer for plant irrigation.

Today, the opportunities for water recycling are many, and fall into seven general categories:

• Agricultural irrigation for food and non food crops
• Landscape irrigation for unrestricted, limited, and restricted access areas
• Groundwater recharge for replenishment and seawater intrusion
• Industrial reuse including cooling water, boiler feedwater, process water, and heavy construction (dust control, concrete manufacturing, curing, and fill compaction, and cleanup)
• Recreation and environmental uses for body contact and non contact applications such as artificial lakes, ponds and fountains
• Nonpotable uses such as toilet flushing, sewer flushing and commercial car washes
• Indirect potable uses such as blending in public surface waters and groundwaters

The states of Florida and California are the nation's leaders in volume of water recycled, with Arizona, Florida, Hawaii, Nevada, Texas and Washington all actively recycling water as well. Water recycling is anticipated to grow exponentially in the future as water is a limited resource. California is addressing this issue by establishing water recycling goals, the most recent being recycling 1,000,000 ac-ft of water per year by 2010.

The U.S. Government does not regulate water recycling, rather, U.S. EPA has published guidelines (U.S EPA, 2004) and individual states have developed regulations or standards for water reuse applications. Regulations and guidelines become more stringent and restrictive as the degree of human contact with reclaimed water increases. Typically, regulations and guidelines for nonpotable applications are focused on the control of pathogenic organisms. Potable applications include control of both microbial and chemical constituents.

State regulations frequently specify the type of treatment required. For instance, where human contact with recycled water is incidental or not likely to occur, a low level of wastewater treatment is usually permitted, i.e. disinfected secondary treated effluent. Where human contact is likely to occur, most requirements specify tertiary treatment. The State of California's laws pertaining the recycled water are published together in a book commonly referred to as the Purple Book (State of California, 2001), which may be accessed online (http://www.dhs.ca.gov/ps/ddwem/publications/waterrecycling/purplebookupdate6-01.PDF).

Agricultural and landscape irrigation are the largest uses of recycled water in the country, although Florida does not fit this overall pattern, using a significant amount of recycled water for other uses such as dual plumbing systems in municipal buildings, and for fire fighting purposes. Use of recycled water by industry generally occurs at large facilities such as power plants, oil refineries, and steel manufacturing facilities where the primary use of recycled water is for cooling, heating, material conveyance, rinse water, and equipment and facility cleaning. However, regulations are generally not concerned with water quality issues such as mineral content and total dissolved solids that are important for many industrial uses. Some industries can use recycled water directly, whereas others may need to provide supplemental treatment, especially when the recycled water is to be used for boiler feedwater, manufacturing, or applications such as chip manufacturing that have very specific water quality constraints. In cooling and heating applications water quality characteristics are of concern because of the potential for scaling, corrosion and biofouling in piping, cooling towers, and heat exchangers.

Specific water quality parameters of concern for industrial users, their related issues, and select control options are listed below:

• Alkalinity (carbonate and bicarbonate) - pH stability and corrosion - softening, dealkalization
  
• Ammonia - Affects free chlorine residual, causes stress corrosion in copper-based alloys, and stimulates microbial growth - Nitrification and air stripping.

Nitrification and air stripping:

• Calcium and magnesium - Scale formation - Nanofiltration (NF), reverse osmosis (RO), and ion exchange
• Hydrogen sulfide - Corrosion, odors
• Iron - Scale formation, staining - Green sand filtration, membrane filtration (NF and RO)
• Nitrate - Stimulates microbial growth, interferes with dyeing of textiles - Denitrification
• Organic compounds - Biological fouling, microbial growth, slime and scale formation, foaming in boilers - Biological treatment
• pH - May affect chemical reactions, and the solubility of minerals and metals
• Phosphorus - Scale formation, stimulates microbial growth - pH adjustment, biological nutrient removal
• Silica - Scale formation - Chemical threshold inhibitors
• Sulfate - Corrosion, scaling
• Suspended solids - Deposition, fouling
• Total dissolved solids - Corrosion, scaling - Nanofiltration, reverse osmosis, boiler blowdown

Selecting the appropriate treatment technology for meeting specific water quality should be based on science. Trussell Technologies, Inc. is a leader in applying fundamental science to water reclamation systems and reuse applications.

Our team's expertise includes:
Dr. R. Shane Trussell, who has extensive experience with the membrane bioreactor (MBR) technology, an ideal process for water reclamation systems; on-site work experience at various water reclamation facilities; and design of advanced wastewater projects focused on meeting high reclaimed water quality objectives. Dr. R. Shane Trussell understands the treatment processes needed to cost effectively meet a desired reclaimed water quality goal. He is also a member of the WateReuse Association's Professional Advisory Committee (PAC) for "A Decision Support System for Selection of Satellite versus Regional Treatment Water Reuse Systems."
Dr. R. Rhodes Trussell began his career working on Water Factory 21's groundwater replenishment project, lead indirect potable reuse projects internationally, and is currently the Chair of the Research Advisory Committee for the WateReuse Association.
Dr. David Hokanson, is an industry leader in modeling advanced oxidation processes (AOP), targeted compound removal by activated carbon, and ion exchange technologies and all advanced processes typical for meeting high quality water goals.
Jennifer Aieta has worked extensively in system design and serves as technical editor for Water Reuse: Issues, Technologies, and Applications; a textbook to be published in 2006.

Terminology:
Wastewater: Used water discharged from homes, business, cities, industry, and agriculture. Various synonymous uses such as municipal wastewater (sewage), industrial wastewater, and storm water.
Water reclamation: Treatment or processing of wastewater to make it reusable. This term is often used to include delivery
of reclaimed water to the place of use and its actual use.
Water reuse: The use of treated wastewater for a beneficial use, such as agricultural irrigation and industrial cooling.

References:
U.S. EPA and U.S. AID (2004) Guidelines for Water Reuse, EPA/625/R-04/108, U.S. Environmental Protection Agency and U.S. Agency for International Development, Washington, D.C. (http://www.epa.gov/nrmrl/pubs/625r04108/625r04108.htm)

State of California (2001) California Health Laws Related to Recycled Water “The Purple Book” Excerpts from the Health and Safety Code, Water Code, and Titles 22 and 17 of the California Code of Regulations, California Department of Health Services, Sacramento, California. (http://www.dhs.ca.gov/ps/ddwem/publications/waterrecycling/purplebookupdate6-01.PDF)