Biodegradability index (BDI) as an indicator for effluents quality measurement; a case study based on different industry sectors in Matara District, Sri Lanka

Abstract

This study addresses the crucial need for appropriate indicators to characterize aquatic pollution, given the challenges posed by unrestricted effluent discharge globally. Focusing on wastewater from hotel and tourism industries and vehicle service stations in Matara District, Sri Lanka, we explored the relationship between biological oxygen demand (BOD) and chemical oxygen demand (COD) through the biodegradability index (BDI). Monthly water samples were collected from January 2019 to December 2022, analyzed using standard methods, and statistically evaluated. Results revealed a significant spatial variation in BDI among industry sites, with a modest temporal change. The BOD:COD ratio exhibited a slight increasing trend over time, suggesting factors beyond temporal influence. BDI correlated significantly with temperature, alkalinity, and total suspended solids (TSS), emphasizing its potential as an indicator. The study underscores the importance of complementing the BOD:COD ratio with other indicators for a comprehensive assessment of industrial effluent quality. This research contributes valuable insights into understanding wastewater characteristics, facilitating informed pollution reduction and control strategies in aquatic systems.