When pH decreases, effluent turbidity increases, and sludge rises in the clarifier, what does this indicate?

When pH decreases, effluent turbidity increases, and sludge rises in the clarifier, it typically indicates a problem related to the biological processes taking place within the treatment system. A decrease in pH can result from increased organic loading or a buildup of certain acids produced during microbial metabolism. In this context, denitrification can contribute to lower pH levels depending on the specific conditions in the treatment process.

During denitrification, bacteria convert nitrates and nitrites, which can lead to the production of gaseous nitrogen and organic acids. This process can simultaneously cause sludge bulking, where the sludge settles poorly in the clarifier, leading to increased turbidity in the effluent. So, the conditions described—decreasing pH, higher turbidity, and rising sludge—are characteristic indicators of a potential denitrification problem, where the biological activity is not properly balanced, causing operational issues in the wastewater treatment system.