L-5480 9-08

Onsite treatment systems

Graywater tank

Blackwater tank Figure 1: A home with separate and graywater plumbing systems. Graywater safety

Rebecca Melton and Bruce Lesikar Extension Assistant and Professor and Extension Agricultural Engineer The Texas A&M System

hen homeowners use graywater to water their lawns, they help preserve washed materials soiled with human limited water supplies, reduce the demand for potable water for lawn waste (such as diapers) and water that Wirrigation and decr,ease the amount of wastewater entering sewers or has been in contact with waste. onsite systems. A graywater system may collect water from a single approved source However, homeowners who What is in graywater? or from any combination of those irrigate their lawns with graywater sources. The amount and quality The Texas Administrative Code need to understand the risks and of the graywater depends on the defines graywater as water from these safety issues associated with such use. sources. residential sources: Residential wastewater can be They should know the constituents ✔ of graywater as well as their potential ✔ Showers and bathtubs classified as either blackwater (sew- ✔ effects on human, soil, plant, and ✔ Sinks, except those used for age containing fecal matter or food environmental health. disposal of hazardous or toxic wastes) or graywater. If graywater is materials or for food preparation collected separately from blackwater, or disposal it can be dispersed as water ✔✔ Clothes-washing machines with less treatment than is required The code excludes water that has for blackwater. Table 1 includes a partial list of Table 1. Wastewater constituents from various residential sources. constituents that may be present in Shower Sinks Laundry graywater, illustrating that if some- and bathtub (not kitchen) thing is washed down the drain, it Bacteria • • will end up in the graywater. Several factors affect the com- Bleach • position of graywater, including the Grease and oil • • • quality of the water supply; the resi- dents’ personal habits; soaps, deter- Hair • gents, and cleaners used in the home; High pH • the age and number of residents in the home; the graywater treatment Hot water • • • process (if any); and the length of Nitrogen • graywater storage time. For example, a study in 2001 by Odor • • the University of Arizona found that Organic matter (BOD)† • • a home with two adults and a child had a significantly higher concentra- Phosphorus • tion of fecal coliform (microorgan- • isms found in ) in the graywater than did a household of Soap • • • just two adults. Sodium • Graywater will have higher concentrations of chemicals from Suspended solids • • • detergents and cleaners if strong • • • products are used in the home and †Biochemical oxygen demand, a measure of organic contamination if the products are used often. Also, any treatment of the graywater and Often graywater has already ✔✔ Avoid irrigating edible fruit and the length of time it is stored before come into contact with humans—at vegetable gardens with graywa- application will influence its levels of sinks and in showers and tubs— ter. suspended solids, nutrients, bacteria, before it enters the graywater system. ✔✔ Discourage children from play- viruses, and odor. There is some concern that bacteria ing in areas where graywater is When homeowners use gray- can accumulate and grow in the regularly applied. water for landscape irrigation, they graywater storage system and that ✔✔ Never use graywater to wash should understand that the water graywater can be exposed to people down driveways, patios, or other contains constituents that may influ- who do not live in the house where it impervious surfaces. ence whether it is appropriate for use. originated. In addition to using graywater in As shown by several research stud- To eliminate possible exposure, areas that reduce the risk to human ies, the amount of contaminants in homeowners should choose the health, homeowners should make graywater varies greatly (Table 2). The distribution method and application sure that the system is designed and quality of graywater is lower than that areas carefully. For example, never operated to prevent inadvertent expo- of drinking water but higher than use spray distribution (sprinklers) sure to people: that of raw municipal wastewater. to apply graywater because it is the ✔✔ Prevent cross-contamination by method most likely to cause human using backflow prevention valves. Preventing harm exposure. The method least likely to ✔✔ Direct the overflow from the to people cause human exposure is a subsurface graywater reservoir to an onsite distribution system. The risk that graywater may pose wastewater treatment system or to human health is not as great as is If graywater is applied to the municipal sewer. often assumed. Although many of the soil surface (in a method other than ✔✔ Color-code all graywater com- contaminants in graywater may harm spray), take these steps to prevent ponents with purple markings your health (Table 3), the damage oc- exposure to people: to identify the water in them as curs only if the graywater is ingested ✔ ✔ Apply the graywater to areas that unsuitable for drinking. or otherwise contacted physically. receive little or no traffic. ✔✔ Wear latex or surgical gloves when handling components of Table 2. Concentrations of contaminants in graywater and raw wastewater and the maximum allowable concentrations in drinking water. Graywater studies

Constituent Units Standard Water Drinking Protection (Environmental Agency, 2006) Typical Raw Wastewater (University of Arizona, 2001) Michigan, of University 1974 Urban Water Research Association of Australia (includes kitchen waste) University of Arizona, 2001 University of Arizona, 1991 New Mexico, 1998 Journal of Environmental Health, 1978 University of Arizona, 1995 Barium mg/L 2 <1 41

BOD† mg/L 300 328 159 65 260 149 120

Cadmium mg/L 0.005 0.1 30– Chloride mg/L 250* 25 21 9.0 100 Copper mg/L 1.3 (1*) 0.11 130

CFU/100 107– 8.03 1.4 7.6± 0.8 Fecal coliform mL 10 7 6 10 X10 X10 Log10 Iron mg/L 0.3* 0.11 700

Lead mg/L 0.015 0.04

Manganese mg/L 0.05* <0.05 31

Nitrate/nitrite mg/L 10/1 0.9 0.3 9.3 0.12 1.8

pH mg/L 6.5–8.5* 7.2 7.3 7.5 6.5 6.8 6.7

Phosphorus mg/L 59 8.1 9.3 26

Sodium mg/L 80 73

Sulfate mg/L 250* 117 35 60 23

Suspended solids mg/L 192 33 160 162 40.3

Turbidity mg/L 5 49 100 43 76

Zinc mg/L 5* 0.62 100 *Indicates EPA secondary water quality standard, which means that removal of these constituents is not required. If the concentration exceeds this standard, the effect to the water will only be aesthetic (odor, color, bad taste, corrosion etc). † Biochemical oxygen demand, a measure of organic contamination

the system to perform mainte- Generally, most of the graywater harm depends on the quality of the nance activities, such as cleaning and the nutrients in it will be used by graywater, the type of soil, and the filters. plants, and the dynamics of the soil geology of the site. should break down the other contam- Groundwater may become Avoiding harm inants. If the system is maintained contaminated if it contains large to the environment properly, the graywater should have amounts of industrial chemicals that little if any effect on groundwater (the The greatest environmental effect are not broken down by biological water beneath the ground surface, of using graywater is that it decreases and/or environmental processes. It such as in an aquifer) or surface water the demand for fresh water, preserv- can also become contaminated if the (water in rivers, lakes, and streams). ing limited water supplies. The use of graywater is applied to ponded soils graywater also reduces the amount of However, graywater can pollute or saturated soils. wastewater entering sewers or onsite groundwater and surface water if it is Surface water may be affected if wastewater treatment systems. not applied properly. The amount of the graywater is applied to the ground Table 3. Potential health effects of contaminants. Contaminant Effect Barium Increase in blood pressure

Cadmium Kidney damage

Copper Short-term exposure: gastrointestinal distress Long-term exposure: liver or kidney damage Fecal coliform Short-term effects: diarrhea, cramps, nausea, headaches or other symptoms. Fecal coliform does not cause these symptoms, but its presence indicates that the water may be contaminated with micro- organisms that do cause the symptoms. Lead Infants and children: delays in physical or mental development Adults: kidney problems; high blood pressure Nitrate Infants below the age of 6 months who drink water containing nitrate above the drinking water standard could become seriously ill. Turbidity Although turbidity has no health effects, it can interfere with disinfection and provide a medium for microbial growth. Turbidity mayindicate the presence of disease-causing organisms, including bacteria, viruses and parasites that can cause symptoms such as nausea, cramps, diarrhea and associated headaches. Source: Adapted from U.S. Environmental Protection Agency, 2006 surface and it runs off into streams Sodium not only increases the limiting the amount of harmful or lakes. To limit the risk to surface alkalinity of a soil, but it also can elements entering the graywater water resources, choose a site where greatly damage the soil structure and, streams, such as by selecting a the soil can absorb the graywater and over time, inhibit the soil’s ability to laundry detergent low in sodium. does not allow ponding. Apply the accept water. To counteract the effects graywater at a low rate and distribute of sodium and help restore the soil Reducing effects it uniformly. You may need to move structure and water absorption rates, on plants the drag hose to limit ponding and periodically add organic matter such A study in 2004 by North distribute the contaminants. as or agricultural gypsum to Carolina State University showed the distribution area. Graywater cannot be discharged that graywater’s effect on ornamen- into a lake, river, or stream or into a You can minimize the buildup tal plants depends on the sources ditch leading to these water resources. of sodium and other contaminants of the graywater and the species of by periodically flushing the soil with Reducing effects on soil plant. The study found that graywater fresh water (this includes heavy rain- streams from kitchens (which are not Applying graywater can have fall), rotating the area to which the approved for graywater reuse under long-term effects on the soil, primar- graywater is distributed, and distrib- the Texas code) killed all the plant ily an increase in pH or alkalinity, uting the graywater over large areas. species tested. and an accumulation of sodium. The soil type will also influence Conversely, the plants irrigated Laundry detergents often contain the effect of graywater on the site. For with laundry graywater all survived, alkaline chemicals such as sodium, example, a well-draining sandy soil although some of them differed in potassium, and calcium. Adding will be less affected by water composi- size and physical appearance com- these chemicals to the landscape can tion than will a clay soil. pared to the test group, which was raise the pH of the soil. The amount of water that the irrigated with tapwater. Just as not all Monitor this change by periodi- soil will be able to accept unaffected plants can grow in certain climates cally measuring the soil pH of the depends largely on: and soil types, not all plants thrive distribution area. An acidic soil will ✔✔ The physical characteristics of when irrigated with graywater. For have a pH of 6.9 or lower; an alkaline the soil. For example, do not dis- example, because graywater makes soil will have a pH of 7.1 or higher. If tribute large amounts of graywa- the soil more alkaline, plants that the pH is excessively high (7.5 to 8), ter in an area that drains poorly. grow best in acid soils should not be you can bring the pH closer to neutral ✔✔ The quality of the graywater. used where graywater is applied. (7) by incorporating into the soil an You can improve your graywa- However, a lush landscape can agricultural sulfur or an acidic fertil- ter quality by treating it before be achieved with the proper graywa- izer such as ammonium sulfate. distribution or by preventing or ter distribution methods and plant selection. Of the many types of plants ally have lower sodium content than Plants typically do better if the that could be used, only a small do regular detergents because the soil is allowed to dry between water- percentage of them are damaged by concentrated varieties do not contain ing. Do not apply more water than the graywater. Table 4 shows examples fillers. soil can handle, or the graywater will of plants that should not be used in a Many cleaning agents contain pond. Ponding can result in runoff, graywater reuse area as well as those large amounts of chlorine. Although groundwater contamination, human that do well. the chlorine is often expended in the contact, mosquito breeding areas, and The quality of the graywater can cleaning process, it should still be a plant disease. influence plant health. Plants can be goal to prevent high chlorine concen- Over time, the soil may become harmed by high sodium, boron, and trations in the irrigation water. less able to accept water because chlorine levels in graywater. Sodium The California guide also rec- of the effects of the graywater. You inhibits water intake to the plant, ommended that homeowners with may need to periodically adjust the and large amounts of chlorine can be graywater systems not use detergents application rates and/or distribution toxic. Signs of excessive chlorine and that contain: area size. sodium include leaf burn, yellowing ✔ ✔ Bleaches Summary leaves, and twig die-back. ✔✔ Softeners Although plants require some ✔✔ Whitening ingredients Graywater can meet part of boron for growth, too much boron our landscape’s need for water. To ✔✔ Enzymatic powers can cause problems such as leaf limit health risks to people and the ✔✔ Borax tip and margin burn, leaf cupping, environment, homeowners must ✔ yellowing leaves, branch die-back, ✔ Peroxygen manage the constituents in graywater premature leaf drop, and reduced ✔✔ Sodium perborate properly. Select the soil application growth. ✔✔ Petroleum distillate site and method carefully, take steps You can decrease the damage ✔✔ Alkylbenzene sodium trypochlo- to prevent contact of graywater with from sodium, chlorine, and boron rite people, monitor the soil quality and by reducing the amount of these The amount of graywater used correct it if needed, and choose plants chemicals in the graywater. To do can also influence the health of your that are not sensitive to graywater this, choose your detergents carefully. landscape. Sometimes the amount constituents. The California Water Conserva- produced is only enough to provide tion’s Using Graywater in Your Home supplemental water to the landscape, For more information Landscape: Graywater Guide suggests and additional water is needed to Additional information on using soaps and detergents that are meet the plants’ needs. Other times, graywater reuse systems is available low in sodium-rich “fillers” (ingre- the system may produce more gray- in Extension publication B-6176, On- dients added to the detergent that do water than is needed for the distribu- Site Wastewater Treatment Systems: not affect the cleaning effectiveness). tion area, and the landscape suffers Graywater. Concentrated liquid detergents usu- from overwatering.

Table 4. Plant suitability for graywater irrigation. Plants that will probably not do well with Plants susceptible to high sodium and Plants that will probably do well with graywater chloride graywater Azalea, begonia, bleeding hearts fern, Crape myrtle, deodar cedar, holly, redwood, Agapanthus, Arizona cypress, Australian camellia, foxglove, gardenia, hydrangea, star jasmine tea tree, Bermuda grass, bougainvillea, impatiens, oxalis (wood sorrel), philodendron, cottonwood, fan and date palms, primrose, rhododendron, violets honeysuckle, ice plant, Italian stone pine, juniper oleander, olive, oak, purple hopseed bush, rose, rosemary Source: Using Graywater in Your Home Landscape: Graywater Guide, California Water Conservation This publication was funded by the Rio Grande Basin Initiative administered by the Texas Water Resources Institute of the Texas AgriLife Extension Service, with funds provided through a grand from the Cooperative State Research, Education, and Extension Service, U.S. Department of Agriculture, under Agreement No. 2005-45049-03209.

The Onsite Wastewater Treatment Systems series of publications is a result of collaborative efforts of various agencies, organizations and funding sources. We would like to acknowledge the following collaborators: Texas State Soil and Water Conservation Board USEPA 319(h) Program Texas On-Site Wastewater Treatment Research Council Texas AgriLife Extension Service Texas Commission on Environmental Quality Texas AgriLife Research Consortium of Institutes for Decentralized Wastewater Treatment USDA Natural Resources Conservation Service