If a water sample has a pH of 8.0 and a BOD5 of 200 mg/L, where is it most likely collected from?

A water sample with a pH of 8.0 indicates a slightly alkaline condition, which is typical for many domestic wastewater outputs due to the presence of cleaning agents and the process of biological decomposition. The BOD5 (Biochemical Oxygen Demand over 5 days) value of 200 mg/L suggests a significant level of organic matter in the water, which aligns with typical values for domestic wastewater. This level of BOD5 implies that there is a substantial amount of organic material present that requires oxygen for microorganisms to break down, a characteristic often found in sewage or wastewater from households.

In contrast, stormwater runoff can have varied pH levels depending on the land use and rainfall but generally would not show such a high BOD5 due to dilution and turbulence in stormwater systems. Industrial discharge can also vary significantly in pH and BOD depending on the processes involved but often results in higher values and stronger pollution indicators than those observed in domestic wastewater. A drinking water source typically has a neutral pH (around 7) and much lower BOD values, indicating minimal organic matter presence, as drinking water is treated to remove such contaminants.

Therefore, the combination of an alkaline pH and a high BOD5 suggests that the water