Standards for Chemical Quality
1. EPA Regulated Chemical Contaminants. The requirement for “potable, uncontami-nated” drinking water for “ordinary animals”, as stated in the Guide, can be interpreted to mean that animal drinking water should, at a minimum, comply with the EPA’s Primary (health-related) Drinking Water Regulations for human consumption. This is similar to the requirement that states USP Purified Water must be prepared with water complying with the EPA regulations. The EPA regulated contaminants are listed in Table 1.
Recommendation: Water should meet EPA Primary Drinking Water Standards. Test for the list of regulated chemicals at your facility or obtain documentation from your local water utility. Animal facilities that test for these contaminants usually do so 1 to 4 times per year.
2. pH. The Guide specifically mentions pH as something that may necessitate periodic monitoring. The reason for setting a low limit is that low pH water is corrosive and can dissolve plumbing components. This is especially a concern when water contacts brass and copper piping systems where copper, zinc, and lead can dissolve into the animal’s drinking water. Reasons for setting a high limit are that high pH can promote hardness scale precipitation (see number 3 "Hardness" below) and that chlorine disinfection is not as effective at high pH. See the Edstrom Industries document Forms of Chlorine in Water (MI-4148) for more information. Some facilities acidify animal drinking water to pH 2.5 to 3.0 in order to kill Pseudomonas and other common water bacteria.
Recommended ranges for acceptable pH:
• 6.5–8.5 for water that contacts brass and copper plumbing components
• 2.5–8.5 for water in stainless steel and/or plastic piping systems
Note: For most effective chlorine disinfection, pH should be below 7.0
3. Hardness. The reason for setting an upper limit on hardness is that hard water can cause calcium carbonate scale deposits in automated watering systems, which can lead to drink-ing valve leaks and other operational problems. According to the Water Quality Association, water is considered “hard” when the measured hardness exceeds 120 mg/L.
Just knowing the hardness level of water is not enough to predict if it will cause scaling problems. A better predictor is the Langelier Saturation Index (LSI). When the LSI (which is calculated from pH, total dissolved solids, calcium hardness, and alkalinity) is greater than zero, water will have a tendency to scale. See the Edstrom Industries docu-ment Scale-forming Tendency of Water (MI-4170) for more information.
Recommendation: LSI of water in automated watering systems should be less than zero.
4. Total Dissolved Solids or Conductivity. Total dissolved solids (TDS) and conductivity both indicate the total inorganic mineral content of drinking water. Either of these tests can be used to monitor the consistency of quality from water purification processes (such as reverse osmosis), which remove inorganic contaminants from water. The typical con-ductivity of reverse osmosis (RO) water ranges between 1-100 μS/cm, depending on the conductivity of the supply water. Usually, conductivity is measured with in-line sensors. For more information on monitoring water purifications, see Monitoring an RO System (MI4154).
Recommendation: When water is purified by reverse osmosis, deionization, or distillation, the purification process should be monitored by measuring the TDS or conductivity of the product water. Maximum limits should be set based on the supply water quality and the specified performance of the purification process.
5. Disinfectants. An automated drinking water system may contain residual disinfectants from the public drinking water supply or additional disinfectants may be injected into animal drinking water to control bacterial growth. The EPA has proposed/tentative maximum contaminants levels for these common disinfectants:
Chloramine proposed MCL = 4 mg/l
Chlorine proposed MCL = 4 mg/l
Chlorine dioxide tentative MCL = 0.8 mg/l
Recommendation: Drinking water disinfectants should be measured periodically to document the level in animal drinking water. If additional disinfectant is added at the animal facility, the concentration is typically measured 1-7 times per week, both at the point of injection and at the farthest point downstream in the automated watering sys-tem’s piping.
6. Other. Test animal drinking water for any other contaminants that might interfere with research protocols at your facility.
Standards for Microbial Quality
In order to establish microbial quality guidelines for animal drinking water, it is useful to under-stand the guidelines and regulations for EPA drinking water and for USP PW and WFI.
1. Specify Treatment Techniques. EPA regulations specify treatment techniques (filtra-tion, disinfection, etc) in lieu of specific maximum contaminant limits for most microbial contaminants in drinking water. Because of the complexity and cost of testing for water-borne microorganisms, routine examination of water for pathogens is not feasible. Even when specific pathogens are examined, a negative result may be due to the inadequacy of the testing method. Or, it may indicate a safe water quality at that moment when the wa-ter was sampled, but it does not guarantee that safe water can be expected one hour before or after testing.
If this type of guideline were adapted for laboratory animal drinking water, a facility may, for example, specify reverse osmosis water containing a minimum concentration of
normal fluctuation should keep counts under 500/mL. Many animal facilities have set their own limits for HPC bacteria, which range from <1 cfu/mL to <1000 cfu/mL. (Microbiological Survey, Dreeszen, 1996)
Recommendation: For ordinary animals, a total bacteria count alert/action level 100 cfu/mL is achievable in automated drinking water systems and will result in good overall bacterial quality. Lower levels may be desired for immunocompromised animals or for special animal models.
3. Pseudomonas aeruginosa. Pseudomonas aeruginosa is a common water bacteria and is an opportunistic pathogen, which can infect immune-compromised animals. In Edstrom Industries’ Microbiological Survey (Dreeszen, 1996), facilities set goals for Pseudomonas anywhere from <1/100mL to <1000/mL. This is one standard that animal facilities think is important, but the recommended level may depend on the type of animals.
Recommendation: Facilities housing immunocompromised animals should monitor and set limits for Pseudomonas aeruginosa. A common limit set by several facilities is <1 cfu/mL.
4. Viruses and Pathogenic Protozoans.
Although the EPA’s MCLG for viruses and Giardia is zero, detection of viruses and pro-tozoans (which also includes Cryptosporidium) is difficult and not technically feasible for routine analysis of human drinking water.
Recommendation: If viruses or pathogenic protozoans are of concern, perhaps an effec-tive water treatment technique such as reverse osmosis or ozonation could be specified instead of specifying a contaminant limit.