There are many challenges in today’s treatment of poultry water. Water quality standards for growers have not been fully established and most growers are utilizing untreated surface or well water. Problems with waterborne pathogens and scale are common. Because of the poor quality often found in well or surface waters, many growers started utilizing city/community water. The high cost of this trend has affected the bottom line of the grower tremendously. This research will focus on cost-effective water disinfection solutions that do not affect water chemistry or produce harmful disinfection byproducts. In order to justify this approach, currently utilized disinfection methods were analyzed.
Chlorine and its various forms (chlorine gas, chloramine, chlorine dioxide, calcium hypochlorite, sodium hypochlorite, etc.) have been utilized as disinfectants in public water supplies for about a century. In poultry, there is a growing focus on oxidation reduction potential (ORP) levels without consideration of the water’s pH. Growers are actually over chlorinating their water to reach target ORP levels. This is significant because recent studies have shown that chlorine may directly or indirectly be the principal cause of many forms of cancer.
The EPA adopted a trihalomethane regulation in 1979 to limit the allowable level of carcinogenic disinfection byproducts (DBP) in drinking water. Although chlorine is a good disinfectant, it also can form trace amounts of a DBP called trihalomethane (THM) (Swichtenberg , 2003). THMs are chemicals that are formed when organic materials (e.g., decaying trees and leaves as well as urban farm run-off) combine with free chlorine. This has caused great concerns about using chlorine in recent years and the EPA and water companies have searched for ways of reducing these byproducts.
Chloramines are actually used as DBP inhibitors in 30% of the nation’s surface water supplies and are expected to grow to 65% within 10 years (Long, 2005). Chloramines are formed by the mixture of chlorine and ammonia in water. Chloramines can also affect the palatability of water. Chlorine dioxide can also be utilized as a DBP inhibitor. When added to chlorine, a reduction in total trihalomethane (TTHM) has been observed (Rittman, et al., 2002). At the same time, chlorine dioxide is known for producing chlorites that are identified as causing hemolytic anemia (Condie, 1986). Currently, the maximum contaminant level for total THMs is 0.1mg/L in public drinking water.
Gasified chlorine is becoming more prevalent in poultry production. Chlorine gas (Cl2) and chlorine dioxide (ClO2 also referred to as anthium dioxide) can be generated onsite or delivered by specialty shops. This is by far the most dangerous disinfectant available on the market today. In fact, chlorine gas was utilized in chemical warfare on our troops during World War II. The greatest concern is that chlorine gas will create organochlorines. Organochlorines are formed when gasified chlorine comes into contact with organics. Organics can include tannins, algae, bacteria, and biofilms. Their chlorine-carbon bonds are very strong which means they do not break down easily and they resist metabolism. Organochlorines tend to be bioaccumulative and are stored in fatty tissues. As we move up the food chain, the problem becomes more severe. When a predator eats another organism, any fat-soluble substance in the prey that the predator does not digest will be retained in its fats (Thornton, 2000). It is comparable to mercury poisoning in the fact that organochlorines can be passed through the food chain and has been observed in breast meat of ducks (Tsuji et al., 2007, Braune et al., 1999, Braune and Malone, 2006,). This can potentially be a huge liability for the poultry industry.
Ozone has also received a lot of attention recently. It is highly effective for deactivating all groups of organisms (particularly viruses and bacteria) and it can treat high volumes of water. Ozone may be the strongest and most capable disinfectant against cryptosporidium. However, it does have its disadvantages as well. Ozone can produce excessive bromates (which is a potential carcinogen) if the water contains bromide (Siddiqui, et al., 1995). It also possesses a reduced efficacy in cold water. Ozone also does not provide a persistent residual disinfection capability, may require high capital investments, and has relatively high operating and maintenance costs (Funyak, 2003).
Ultraviolet (UV) disinfection is becoming more popular and economical than ever before. UV light is a point-of-contact disinfection system that is highly effective in the inactivation of protozoa (viruses remain most resistant) and does not require the addition of any chemicals, requires short contact times, and posses no known DBPs. It does this without altering the chemistry, taste, and quality of water. However, turbidity (defined as a decrease in the transparency of a solution due to the presence of suspended and some dissolved substances, which causes incident light to be scattered, reflected, and attenuated rather than transmitted in straight lines) however, does affect the quality of disinfection because of what is known as the shadowing effect. Also, as in the case of ozone, UV has no residual disinfection capacity.
Acidification of water using sodium bisulfamate or citric acid has shown promise in reducing bacteria levels in poultry water. However, acidification is not a disinfection process. Its affect provides a less habitable environment in which microorganisms can grow. It was widely accepted that acidification of water led to increased feed conversion. A recent study has reported the opposite (Watkins et al, 2005). Also, research on pathogen reduction has shown that chickens fed with acidified feed developed a relative growth retardation that increased during the first two weeks before it stabilized (Heres et al, 2004). It is then plausible that when broilers are provided acidified water combined with acidified feed, it could detrimentally affect feed conversion and possibly lead to a condition of acidosis. Water with too low of a pH could also corrode plumbing, nipples, foggers, and shorten the life of cool cells.
In the United States and abroad, transition metal ionization (TMI) has been used for years as an alternative to chlorine for disinfection in many applications. Copper-silver ionization has been proven to be very effective against some of the most resistant organisms, such as Legionella, in hot water systems and has proven long lasting residual disinfection capabilities. Copper ions, in the form of copper salts, have been utilized for years in livestock feed to kill and prohibit the growth of Salmonella, E. coli, and Campylobacter. Research on copper surfaces in processing facilities has shown its ability to control Salmonella enterica and Campylobacter jejuni (Faundez, et al., 2004).
Even though the hazards associated with chlorine are known, it is still the most common disinfection method. There is sufficient evidence that TMI can offer superior disinfection capabilities over currently utilized methods without changing the water chemistry or producing harmful disinfection byproducts. It is further believed that the proposed disinfection method will provide required nutritional trace elements to broilers that can help build immunity against common avian pathogens. The USEPA is spending millions of dollars to research disinfection alternatives that do not produce DPBs. The industry focus does not need to be on the reduction of DBPs such as TTHM, but on eliminating them altogether.
Copper-silver ionization is becoming more widely accepted as a disinfection method, especially in hospital hot water systems. The biocidal effect of copper and silver stems from a combination of mechanisms. Positively charged metallic ions attach to the negatively charged bacteria cell membrane and cause cell lysis and death (Britton, et al., 1978; Freedman, et al., 1968; Slawson, et al., 1990). The copper ions disrupt the enzyme structures of the cell allowing the silver ions to penetrate inside where they rapidly kill the cell’s life support system. This is because the positively charged silver and copper ions have an affinity for electrons and when introduced into the interior of a bacterial cell, they interfere with electron transport in cellular respiration systems. Metal ions will bind to the sulfhydryl, amino and carboxyl groups of amino acids, thereby denaturing the proteins they compose. This renders enzymes and other proteins ineffective, compromising the biochemical processes they control. Cell surface proteins necessary for transport of materials across cell membranes also are inactivated as they are denatured.
When copper binds with the phosphate groups that are part of the structural backbone of DNA molecules, the result is the unraveling of the double helix and consequent destruction of the molecule (Meyer, 2001). Copper concentrations of 0.2 to 0.4 mg/liter and silver concentrations of 0.02 to 0.04 mg/liter are recommended for sufficient disinfection levels according to in vitro and field studies (Lin, et al., 1996; Liu, et al., 1994; Liu, et al., 1998).
Zinc ionization utilized in water treatment has not been researched but zinc is often added to feed and antibiotics. Significant growth-promoting effects were observed in broilers receiving zinc-bacitracin (Engberg, et al., 2000). This is probably attributable to the significant reduction in the number of coliform bacteria (C. perfringens and Lactobacillus salivarius) in the ileum of zinc-bacitracin fed birds. It should also be noted that zinc-bacitracin had no influence on enterobacteria counts in the ileum. Zinc, like copper, has excellent antimicrobial effects.
Unlike chlorine, transition metal ionization does not result in dangerous halogenated organic by-products such as trihalomethanes, chloramines and chloroform. Also, these ions are stable, making it easier to maintain an effective residual disinfection (Meyer, 2001). Furthermore, the ions will remain active until they are absorbed by a microorganism. However, using soluble metal salts as a source of these ions and monitoring their concentrations to maintain consistent effects is cumbersome at best. Consequently, most modern ionization systems use electrolytic ion generators to control the concentrations of the dissolved metals. The electrolytic ion generator is the most cost effective approach and is the approach that will be utilized in this study.
The efficacy of TMI disinfection is dependent upon several variables. The concentration of metal ions in the water has to be of sufficient levels and is determined by the water flow, the volume of water in the system, the conductivity of the water, and the present concentration of microorganisms. This is similar to chlorine in the fact that active disinfection levels decrease upon contact with microorganisms.
Copper-silver ionization is highly effective against Legionella, known to be resistant to most disinfectants and will even disinfect the bio film this bacteria produces. The copper ions remain within the bio film, causing a residual effect. When copper and silver ions are added to water constantly, the concentration of Legionella bacteria remains low. Copper-silver ionization also has a deactivation rate slower than that of ozone or UV. Another benefit of copper-silver ionization is that ions remain in the water for a long period of time causing long-term disinfection and protection from recontamination (Neither ozone nor UV has this capability). Copper and silver ions remain in the water until they precipitate and are absorbed by bacteria or algae, or removed from water by filtration.
The TMI systems have several advantages that include:
- Installation and maintenance is easy
- Efficacy is not effected by water temperatures
- Very good residual disinfection protection
- Recolonization is delayed because transition metals ions kill rather than suppress
- Effective on even on Legionella and Cryptosporidium.
Supplemental copper intake in poultry and swine diets has shown growth promotion abilities (Burnell et al., 1988; Cromwell et al., 1989; Dove, 1993) which are believed to be attributable to the biocidal affect of copper (Varel et al., 1987). Contradictory findings have been published on intake level where increased dietary copper levels (above 120 ppm) have shown adverse growth responses and toxicity (Kashani et al., 1986; Harms, et al., 1987). These discrepancies may be attributable to the difference in breed, age, length of treatment, type of diet, and growing conditions among the various experiments. It should also be noted that only 1.3 ppm is the EPA standard of copper in drinking water for human consumption (Amount tested in the aforementioned research was 100 times above this amount) and even the EPA regulations are substantially higher than what is being proposed as the disinfection level (