Comparative Analysis of Inlet and Outlet Water Quality Using Water Quality Index from the Ghorashal Fertilizer Industry, Dhaka

Abstract

Industrial wastewater from fertilizer industries is a major source of environmental degradation in Bangladesh, especially for rivers near clusters. This study focuses on the inflow and outflow of the official water from the GUFI (Urea Fertilizer Industry) in Dhaka. Samples were collected fortnightly for two months, and all the methods recommended by APHA (2017) were followed when determining physical parameters (temperature, color, odor) or chemical parameters (pH, electrical conductivity [EC], total dissolved solids [TDS], dissolved oxygen [DO], biological oxygen demand [BOD], and chemical oxygen demand [COD]). Wastewater from the GHURASAL UREA factory was effective in practice, initially altering pH values to an average of 8.2. Both BOD and COD levels were cut by about 60% relative to their raw values, again meeting DoE standards. Outlet EC values (mean 1405 µS/cm) exceeded the DoE specifications of 1200 µS/cm, outlet TDS (1715 mg/L) surpassed the WHO's recommended limit, and outlet DO levels (mean 3.6 mg/L) fell short of the WHO's and USEPA's criteria for aquatic life, which require a minimum of 5 mg/L. The inlet wastewater, with a WQI of 148, is unequivocally classified as "Unsuitable" or "Polluted." This extreme value is a quantitative manifestation of the heavily contaminated nature of the raw industrial discharge, corroborating the observed high organic loads, critical oxygen depletion, and elevated ionic strength. The treated effluent shows a marked improvement, with the WQI falling to 78, placing it in the "Very Poor" category. This 52% reduction in the index value is a strong quantitative testament to the overall functionality of the wastewater treatment plant. These results suggest that, although the treated effluent meets national standards, it is ecologically problematic on a global scale. Over time, this situation may lead to gradual pollution, land degradation, and even public health problems due to infectious diseases.