The role of faecal coliforms in water quality assessment

The paper aims to evaluate the role of faecal coliforms in assessment of water quality. The study was conducted on the Neretva River in Bosnia and Herzegovina. The sampling was performed bimonthly, over 12 months at seven selected sites. APHA (1995) methods were used. The raw data of temperature, pH, conductivity, oxygen saturation, nitrogen, total phosphorus, and faecal coliforms were transformed into unitless subindices on a scale of 0 to 100 (Ridanovic et al., 2012). NWQI was calculated as a harmonic mean of subindices. Application of NWQI as indicator of water quality was demonstrated through spatial analysis of water quality. Results show a significant decrease (>50%) of water quality. Linear regression was used to assess which parameter has the greatest influence on NWQI value. Results suggest that all tested parametres are strongly connected to NWQI (nitrogen, R2=0.7455422), (total phosphorus, R2=0.887803), (oxygen saturation R2 =0.696964), (pH, R2=0.595705). However, NWQI value was the most significantly affected by faecal coliforms (R2=0.9788). Subindex values for conductivity and temperature were 100, hence their connection to NWQI cannot be analysed by linear regression. Results show how much NWQI changes with a change in one or more subindices, as it assumes a causal relationship between them.