W ater is the most limited resource for managing turf facilities such as golf courses. It can be a very expensive and limited in supply, so turf managers have to consider using alternative sources. The use of effluent water for irrigating turf is a viable alternative that provides an inexpensive and unlimited supply and allowing authorities to dispose of wastewater with minimal environmental impact.
Turf is an excellent means of disposal for treated effluent because it has a filtering effect, utilizing the nutrients in the water and reducing the potential for pollution. It is estimated that less than 5% of water used on golf courses is treated effluent and there is enormous potential to increase its use.
However, there are a number of water quality factors that have to be considered in using effluent water on turf. If soil is irrigated with certain water over an extended time, the soil assumes the characteristics of that irrigation source. Total dissolved salt (TDS) concentration is normally used as an indicator of water quality, but it is the composition of these salts that has to be evaluated for its direct and indirect effects on turf. Effluent water is inferior quality to most water supplies e.g. Town, bore, river, dam, and can be detrimental to turf if not managed properly.
Water Analysis
To understand the impact of effluent water on turf, it is essential to have an irrigation suitability test. This involves analyzing all the major mineral elements in the water rather than the biological components. The analysis should include at least pH, salts, Ca, Mg, Na, Fe, Bicarbonate, Carbonate, Chloride, Sulphur, Boron. It is also useful to know the concentration of nutrients, such as Phosphorus and Nitrogen (Ammonia and Nitrate). An important ratio that should be calculated is the Sodium Absorption Ratio (SAR) and the adjusted SAR.
It may be necessary to sample the water two or three times per year to determine if there are seasonal fluctuations in water quality. Using soil tests will monitor the impact of harmful elements such as sodium and total salinity.
It is important to have an understanding of how these minerals affect turf to manage effluent water effectively.
Check the Source
It is advisable to investigate the sewage treatment plant to determine the extent and type of processing. Treatment plants vary greatly in size and processing method and the quality of water can fluctuate depending on the source. It is important to get an indication of the variations that influence the quality of output, such as the amount of industry in the area or seasonal fluctuations in population. The criteria used for the discharge standards are quite different to irrigation suitability.
Evaluate Water Quality
Effluent water normally has a number of undesirable characteristics, including high pH, high bicarbonate, excessive sodium and moderate to high total soluble salts.
pH: Long-term use of effluent will cause alkaline conditions in soil resulting in poor fertilizer response and reduced nutrient availability, e.g. iron and manganese deficiency.
Bicarbonate: The sodium hazard is increased because bicarbonate locks up the available calcium that is essential for good soil structure, forming insoluble calcium carbonate.
| Sodium: This is the most destructive element to soil structure. Sodium causes soil particles to disperse and form an impermeable crust that impedes water movement and causes soil compaction. SAR is the ratio of sodium to calcium and magnesium and indicates the potential impact of water on soil structure.
Salts - In compacted soil
conditions it is difficult to leach salts and even a moderate concentration in water can accumulate to cause turf stress. It is common for effluent to contain high chloride levels, resulting in the formation of sodium chloride salt in the soil.
Another consideration is the concentration of Nitrates and Phosphates in water. While these nutrients supplement fertilizer applications, leaching into ground water may be a problem on sand profiles. It is useful to calculate the annual quantity of nutrient applied in water to determine any potential problems.
Symptoms of poor quality water
It may take several years for the effects of poor quality effluent water to become evident due to the cumulative effect in the soil. The turf damage shows up mainly during summer when effluent use is at its peak and there is little flushing with fresh water. The most common symptoms include wilting and drought stress, gradual thinning and yellowing and increased disease activity such as pythium. The soil becomes compacted and holds excessive moisture in the surface creating conditions for the development of an anaerobic black layer in the soil profile. The turf also responds poorly to fertilizer and chemical treatments.
Pic 2. Turf Solution Master Injection System used for gypsum treatment of effluent water.
Treatment options
The objective of treating water-related problems is to maintain good drainage to leach undesirable salts from the soil profile. It is very difficult to remove salts from the water so the best option is to flush them out of the root zone.
It is more effective to treat the source of the problem in the water rather than symptoms in the soil. Conventional treatment methods such as aeration and soil-applied gypsum provide short-term relief but are negated by ongoing irrigation with effluent water. Irrigation injection with Gypsum (e.g. Aqua Cal) is most effective at treating the calcium / sodium imbalance in the water and will relieve turf stress by maintaining well-aerated and drained soil profiles.
In water with high bicarbonate content, the effectiveness of Gypsum is reduced and acid injection (e.g. Phairway) has proven successful. This treatment has the effect of breaking down bicarbonates and releasing soluble calcium into soil solution. The result is improved soil structure, which relieves compaction and black layer conditions, allowing leaching of undesirable soluble salts.
Conclusion
It is possible to deal with the problems associated with using treated effluent water, but it is important to know exactly what you are dealing with. Use soil and water analysis to determine the potential impact of effluent water on turf and the most suitable treatment method.
Ref: Ninemire, S. (1997) Effluent water has positive potential.
Grounds Maintenance, May 1997. |
