Comparison of river and drinking water quality of infiltration intakes based on statistical colour data

Comparison of drinking water and river water colour at infiltration intakes has been carried out. It was found that at infiltration water intakes the drinking water colour is 3.5-4 times lower than the colour of river water, which is characterized by pronounced seasonal fluctuations (from 3.8 to 99 deg at IWI1 and from 5 to 106.9 deg at IWI2). Thus, in drinking water, the values of the indicator vary from 5 to 5.3 deg in CWT1 and from 4.9 to 8.3 deg in CWT2. The time series analysis showed that the colour of river and drinking water is seasonal. The contribution of the seasonal component is 66% and 48% for river water in the stations, and 10-18% for drinking water in the CWT. A significant contribution (79 to 89%) to the variation of the indicator in drinking water is made by random variable. Correlation coefficients calculated from monthly averages revealed a weak relationship (on the Cheddock scale) between river and drinking water colour, whereas correlation coefficients calculated from monthly averages of colour in the model year characterise the relationship at IWI1 as high and very high at IWI2. When comparing temporal variations of drinking and river water colour in the model year, it was found that the values of the indicator are maximum in May. The construction of cross-correlation functions on the average monthly values of the indicator for the whole observation period and in the model year showed that there is a relationship between the colour of river water and drinking water. It is revealed that at infiltration water intakes, when river water passes through filtering layers, the efficiency of well water colour reduction differs for different water intakes.