Application systems and facilitation for water sanitation

To achieve and sustain effective water sanitation, application equipment and its correct use are just as important as the type of sanitiser used. Effective water sanitation requires:

• effective pretreatment of the water
  
  
• correct dosage of sanitiser
  
  
• adequate contact time
  
  
• reliable operation
  
  
• accurate monitoring in real time
  
  
• avoiding contamination post-sanitation
  
  
• adequate water storage and appropriate configuration of storage.
  
  

4.3.1 Pretreatment  of water

High organic load is an impediment to effective sanitation of surface water, which can be further compounded by the presence of other chemicals such as mineral salts, nitrogenous compounds, iron and colloids (silicates). The pH of water and the level of oxygenation will also influence the efficacy of sanitation. Seasonal factors may also affect water quality, for example additional rainfall or low rainfall requiring admixtures of bore water. These factors will affect the need to pre-treat the water and will have some bearing on the  type of sanitiser used.

Before any technical decision is made about water pretreatment, it is essential that a complete analysis of the surface water is done. The testing should include a complete chemical analysis (pH, total dissolved solids (TDS), chloride, nitrate, nitrite, sulphate, iron, copper, magnesium, manganese, zinc, sodium, and calcium), turbidity, biochemical oxygen demand (BOD) and a microbiological analysis (total coliforms, E.coli, faecal coliforms). Pretreatment by desalination does not remove microbial pathogens, so sanitation of the treated water is still required.

Other pretreatments include sand filters and  flocculants to remove solids and organic loads (see Appendix). Removal of high levels of iron can be achieved by aerating or treating the water with an oxidiser (chemicals which flocculate4 the iron), followed by the use of settling tanks. There may also be the need for pH adjustment using hydrochloric or phosphoric acids.

Biofilms are an impediment to effective sanitation and should be cleared from lines with flushing and the use of oxidizing sanitisers such as chlorine dioxide and peracetic acid. In some cases where biofilms have been long standing and associated with water pipe corrosion, it is necessary to replace the water lines.

All of these pretreatments require an understanding of  the science involved and an investment in capital to achieve the required outcome.

4.3.2 Dosage of sanitiser

The correct dosage of chemical is essential to achieve effective sanitation of surface water. For liquid addition, dosage equipment must be able to deliver the correct amount of sanitiser to a measured quantity of water. This can be done either via mechanical flow detection pumps, electronic pulsating digital solenoid driven diaphragms, or peristaltic pumps (see Appendix). For the addition of chlorine dioxide, ozone and crystalline iodine systems, the technical aspects of application and dosage are more complicated and require the support of an adequately qualified and trained distributor.

The ongoing maintenance of such equipment is critical. The choice of applicator is influenced by availability of power and cost.

4.3.3 Adequate contact time

Adequate contact time is essential to ensure that microbial pathogens are inactivated prior to the delivery of water to poultry. The duration of contact time is dependent on the contaminant, the quality of the water, the type of sanitiser used and the temperature of the water. Such detailed information is not always available in the field situation and producers therefore need to be conservative about contact time. While different sanitisers act at different rates to inactivate particular avian pathogens, two hours at the recommended sanitiser concentrations is suggested as the minimum contact time. Achieving this benchmark will ensure a high level of confidence for achieving effective water sanitation for most systems and conditions.

Ultimately the only way to ensure that contact time has been adequate is to undertake monitoring for microbial contaminants. While it is not usually practical to test for viruses, bacteria can be used as an indicator.

4.3.4 Reliable operation of equipment

The continuous use of water by poultry operations necessitates continuously effective sanitation of surface water. Even temporary failure of effective sanitation increases the risk of incursion of a water-associated avian pathogen. The purchase of better quality equipment is a small capital outlay considering the importance of the required outcome. While operational aspects of the equipment may fail (such as electronic mechanisms, seals, and casings) there are also maintenance issues (such as air locks, corrosion and filter blockages) that need to be routinely attended to. For more sophisticated set-ups, a maintenance contract from the supplier is often necessary, and the assurance that there are readily available replacement parts.

When buying equipment from overseas, it is important to ensure that it is compatible with Australian standard fitting sizes and electrical input requirements.

4.3.5 Monitoring

It is essential that the effectiveness of equipment can be monitored. This can be done using inbuilt sensing equipment with remote readouts, or through manual measurements of flow rates and dosing volumes. Monitors can also be alarmed to warn the producer of a failure. Simple manual checks to ensure that the correct amount of sanitiser is being used can provide an effective cross-check.

4.3.6 Avoidance of contamination post-sanitation

Effective water sanitation can be undone by allowing recontamination after treatment. Treated water should be transferred in sealed systems and into sealed tanks. There should be no other source of water entering the treated water, such as untreated rainwater. If the system is closed, then falling sanitiser levels in the stored water are of no consequence as the avian pathogens will already have been inactivated and there is no opportunity for recontamination. The principle of maintaining measurable chlorine at the drinker level is not of paramount importance if the water has been effectively pretreated. The presence of a measurable level of sanitiser at the level of the drinker does give the producer more confidence that effective sanitation is being carried out and also aids in controlling the non-specific build up of coliforms, algae and biofilms. Residual activity is particularly important for water distribution systems.

4.3.7 Water storage

Effective sanitation, adequate contact time, sealed storage and reliable equipment operation can only be achieved with the correct (and coordinated) configuration of untreated water delivery, treatment, storage and treated water delivery (Appendix). This means that where the treatment of surface water is required, installation of a number of storage tanks of appropriate size that can store and deliver the treated water in a strategic manner will be required. The procedure of injecting chlorine directly into the main water supply line to the shed does not allow adequate contact time. However, with chlorine dioxide the contact time may be adequate.

In addition, the use of only one water tank for sanitising and holding stored water is inadequate, particularly under periods of high water demand, as there will be a replenishment of raw water entering the system that will have inadequate contact time with the sanitising chemical. It is preferable, if not essential, to have a two tank storage system that is solenoid⁵ controlled with high and low level ball valves (Appendix). This allows the delivery of sanitised water after a guaranteed minimum contact time. Alternatively, this may be done manually by draining sanitised water from the main storage tank into secondary storage tanks that supply the daily demand of the sheds. It is also critical that all water supplied to the sheds is sanitised. Sanitising only the drinking water and not the water used for cooling increases the risk of incursion by water-borne pathogens.

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^{5    An electromechanical valve that is controlled by the starting and stopping of an electrical current and usually used as a switch to control the flow of fluid.}