Integrating entropy-weighted water quality index and multiple pollution indices towards a better understanding of drinking water quality in Ojoto area, SE Nigeria

Abstract

The integration of multiple approaches often presents a better and valid interpretation of water quality. In the present study, multiple water quality indices were integrated with multiple pollution indices to ascertain the quality status of drinking water sources (streams, springs, dug wells and boreholes) in Ojoto area, SE Nigeria. Water samples were tested for physicochemical properties such as pH, Na+, K+, Mg2+, Ca2+, Cl–, SO42–, HCO3–, NO3–, Fe, Zn, Ni, Cr, and Pb. Several pollution indices (e.g., Nemerow pollution index, geoaccumulation index, enrichment factor, and modified heavy metal pollution index) utilized in this study revealed that some water samples have high metal pollution, and hence pose high environmental risks. Modified water quality index indicated that the water quality is threatened with conditions departing from natural or desirable levels. However, entropy-weighted water quality index showed that about 57%, 8%, 4%, 4% and 25% of the samples are of excellent, good, average, poor, and extremely poor qualities, respectively. Pollution index of groundwater (PIG) confirmed that 25% of the samples were very highly polluted, and thus unsuitable for drinking purpose. Quantification of contamination (QoC) and the PIG models were successfully utilized in demarcating the proportions of contribution by geogenic and human activities in the pollution of the drinking water sources. However, both models revealed that the deterioration in the water quality is mostly influenced by anthropogenic inputs. Therefore, change in lifestyle pattern and adoption of adequate water management policy are advised.