Wastewater quality indicators
Any oxidizable material present in an aerobic natural waterway or in an industrial wastewater will be oxidized both by biochemical (bacterial) or chemical processes.
Irrigation runoff and water cooling of power stations may elevate temperatures above the acceptable range for some species.
Settleable solids are measured as the visible volume accumulated at the bottom of an Imhoff cone after water has settled for one hour.
[2]: 406–407 Most aquatic habitats are occupied by fish or other animals requiring certain minimum dissolved oxygen concentrations to survive.
[3] Basically, the reaction for biochemical oxidation may be written as: Oxygen consumption by reducing chemicals such as sulfides and nitrites is typified as follows: Since all natural waterways contain bacteria and nutrient, almost any waste compounds introduced into such waterways will initiate biochemical reactions (such as shown above).
The so-called 5-day BOD measures the amount of oxygen consumed by biochemical oxidation of waste contaminants in a 5-day period.
The total amount of oxygen consumed when the biochemical reaction is allowed to proceed to completion is called the "Ultimate BOD".
As an example an effluent consisting of a solution of simple sugars that might discharge from a confectionery factory is likely to have organic components that degrade very quickly.
However a final effluent of a sewage treatment works serving a large industrialised area might have a discharge where the ultimate BOD was much greater than the 5 day BOD because much of the easily degraded material would have been removed in the sewage treatment process and many industrial processes discharge difficult to degrade organic molecules.
The laboratory test procedures for the determining the above oxygen demands are detailed in many standard texts.
[4] Any oxidizable material present in an aerobic natural waterway or in an industrial wastewater will be oxidized both by biochemical (bacterial) or chemical processes.
The nonpoint sources of phosphates include natural decomposition of rocks and minerals, stormwater runoff, agricultural pollution, erosion and sedimentation, atmospheric deposition, and direct input by animals/wildlife.
Point sources of phosphorus may include municipal sewage treatment plants and industrial dischargers.
High concentration of phosphate in water bodies is an indication of pollution and largely responsible for eutrophication.
Remaining concentrations of oxidizing hypochlorous acid and hypochlorite ions may be measured as chlorine residual to estimate effectiveness of disinfection or to demonstrate safety for discharge to aquatic ecosystems.
