Development of wastewater quality index as an assessment tool of treated wastewater quality for sea discharge

The evaluation of the effluent water quality from wastewater treatment plants is fundamental for human health and aquatic environment considerations. Therefore, this research presents a new and specific water quality index for evaluating the effluent water discharged into the sea by integrating the complex set of wastewater qualities into a single reliable value. Two approaches were utilized for this purpose: experts' opinions and statistical analysis using principal component analysis. In the first approach, the opinions of local experts shortlisted the parameters into six important parameters out of a list of 19 with assigned weights varied from 0.160 to 0.174. In the statistical approach, principal component analysis and correlation analysis reduced the parameters to seven accounting for 75% of the variation in the data. Their weights were calculated based on their eigenvalues and ranged from 0.063 to 0.435. The subindices rating curves were developed based on the Kingdom of Bahrain's legislated standards and the weighted arithmetic mean function was used for the aggregation stage. The established water quality indices were applied to effluents from a local wastewater treatment plant, and the obtained results revealed "Class 1: excellent category" discharge quality maintained throughout the year as per the categories proposed in this work. The developed indices proved their effectiveness and reliability in assessing the treated water. The study provides a comprehensive and reliable assessment of treated water quality, and its approach and outputs could have significant implications globally for ensuring the quality of treated water prior its discharge and promoting sustainable development. This research introduces a new water quality index integrating wastewater characteristics into a single reliable value for evaluating effluent water. Expert opinions and statistical analysis identified and weighted key parameters. Six parameters were shortlisted based on expert opinions, while principal component analysis reduced them to seven, accounting for 75% of the data variation. Applied to a local wastewater treatment plant, the indices revealed consistent "Class 1: excellent category" discharge quality throughout the year, highlighting their effectiveness in assessing treated water quality. image Reliable evaluation of the quality of treated wastewater discharged into the sea is essential for protecting human health and aquatic life. The water quality index provides a prompt and efficient judgement of water quality. Kingdom of Bahrain's water quality index (KBWQI) was calculated for the collected samples from wastewater treatment plant using experts' opinions and using statistical analysis methods. The calculated indices gave comparable results and demonstrated that the effluent quality released into the sea was excellent throughout the year and their reliability to be used for similar environment regionally and worldwide.