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Water Quality Index For Groundwater On Dairy Farms In Central South Africa

Congress: 2015
Author(s): Leana Esterhuizen (Bloemfontein), Annabel Fossey
Central University of Technology, Free State1

Keyword(s): Sub-theme 2: Surface water and groundwater,
AbstractIntroduction

Dairy farms in central South Africa depend mostly on groundwater for domestic needs and dairy activities. Dairies use water for all the steps in the dairy, including cleaning, sanitation, heating, cooling and floor washing. Dairy farm effluent, which refers to manure and urine deposited throughout the milking process, is diluted while washing the milking shed floor. In South Africa most dairy effluent is discharged directly onto pastures and land (Strydom et al., 1993). It has been shown that animal waste in dairy effluent is a major source of pollution of streams and groundwater.

The aim of this study was to assess groundwater quality on 34 dairy farms in central South Africa. The objectives were firstly, to develop a health-related water quality index for groundwater, and secondly, to apply the index to groundwater measurements collected in 2009 and 2013.

Material and methods

Groundwater samples were collected on 34 dairy farms located in central South Africa during 2009 and 2013. Sixteen groundwater quality parameters were tested, namely, electrical conductivity (EC), pH, total hardness, chloride (Cl), sulphate (SO4), phosphate (PO4), nitrate (NO3), fluoride (F), calcium (Ca), magnesium (Mg), sodium (Na), potassium (K), heterotrophic plate count (HPC), total coliforms and Escherichia coli. Total dissolved solids (TDS) were estimated by multiplying EC by the factor of 6.5. The water quality data of the two sampling years were firstly compared with one another to ascertain whether the groundwater quality status had changed over time, and secondly, the measurements were compared to the South African National Standard for drinking water(SANS 241, 2011) to determine compliance. A health related water quality index that describes the overall quality of a source was also developed for groundwater to be used by non-professionals. The index was developed after critically reviewing and adapting three prominent water quality indexes, namely, Weighted Arithmetic (Brown et al., 1972), Weighted (Jerome and Pius, 2010) and the Canadian Council of Ministers of the Environment water Quality Index (CCME, 2001). Eight health related parameters were identified and health limits assigned. The different indexes were calculated and were compared to a manual rating of the raw data to assess their accuracy. Because the calculations of the Weighted method was closest to the manual rated data, the methodology of this index together with the newly assigned health limits were then applied to the data of the two sampling years.

Results and Discussion

Four parameters in 2009 and six in 2013 exhibited 100% compliance with the standard (Table 1). Three parameters, namely, nitrate, E. coli and total coliforms showed relatively low compliance across the farms and years. Approximately one third of the farms were non-compliant for E. coli and more than 50% for total coliforms in both sampling years. For hardness, almost all the farms were non-compliant in both sampling years. T-tests revealed that only three of the parameters demonstrated significant change from 2009 to 2013, namely, pH (t = 3.165; p = 0.002), hardness (t = 2.113; p = 0.021) and potassium (t = 1.743; p = 0.0453).

Table 1: Summary statistics of the water quality parameters measured in 2009 and 2013.

Eight health-related water quality parameters were identified and used to calculate water quality indexes, using the formulation of the Weighted method. Each water quality parameter was described in terms of drinking water and food preparation qualities at the specified health limit (DWAF et al., 1998), which were overall more stringent than the drinking water quality limits. These health-related parameters were turbidity, pH, total hardness, chloride (Cl), sulphate (SO4), nitrate (NO3), total coliforms and E. coli.

The water quality of the different farms was classified according to a five-point rating scale. The number of farms with acceptable water quality (classified as excellent and good) decreased from 17 in 2009 to 11 in 2013 (Table 2). Whereas, the number of farms with unacceptable water quality (classified as poor, very poor and unacceptable), increased from 17 in 2009 to 23 in 2013.

Table 2: Water quality index values calculated for farms using three different indices

Conclusion

Groundwater quality on dairy farms in central South Africa appears to be declining. Because groundwater is the only water source in this area, serious revision of effluent disposal methods is required to contain and limit pollution of groundwater.

References

1. Brown, R.M., McCleiland, N.J., Deinimger, R.A. and O'Conner, M.F. (1972) A water quality index crashing the psychological barrier. Proceedings of the International Conference on Water Pollution Research, Jerusalem 6, 787-797.
2. Canadian Council of Ministers of the Environment (CCME). (2001) Canadian water quality guidelines for the protection of aquatic life: CCME Water Quality Index 1.0, User's Manual. In: Canadian environmental quality guidelines, 1999, Canadian Council of Ministers of the Environment, Winnipeg.
3. DWAF (Department of Water Affaires and Forestry). (1998). Quality of domestic water supplies. Vol 1, Second edition. No:TT101/98.
4. Jerome, C. and Pius, A. (2010) Evaluation of Water Quality Index and its impact on the quality of life in an industrial area in Bangalore, South India. Am. J. Sci. Ind. Res. 1(3), 595-603.
5. SANS (South African Bureau of Standards). (2011) Drinking water. Part 1. Microbial, physical, aesthetic and chemical determinants. Pretoria: SABS. (SANS 241-1:2011).
6. Strydom, J.P., Mostert, F.J. and Britz, T.J. (1993) Effluent production and disposal in the South African dairy industry: A postal survey. Water SA 19(3): 253-258
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