My textile wastewater had a 9.6 pH but had a lack of DO (DO 0,3-0,5 mg/l). Is that normal?
There is no physical-chemical connection between pH and DO.
Your wastewater is likely low in oxygen because something comsumes the oxygen or because it has been heated.
pH is related to the presence of free carbon dioxide and not with DO. Textile waste water generally has high BOD, COD, TSS etc. probably, high chemicals and / or some organic pollutants result in consumption of oxygen from water biologically & chemically. And this result in low DO values in the waste water.
I think, there is no any direct relation between DO and pH in wastewater, but generally for hydrolysis and oxidation you will need high DO and at lower DO high BOD case (your textile sample), the sample may feel anoxic/ anaerobic environment leading to basic pH.
Rizal,
in your special case the following relation may be present. High electrolyte concentration - reduced oxygen solubility.
Thank you everyone, all of your answers is really really helpful
Atleast you got some DO..in many cases we get absolutely anoxic conditions and even you cant get ur BOD correct even at 100 times dilution because the oxygen is fully consumed at day 3 and you are left wid a white ppt.
High salt concentration cannot alone explain the low dissolved oxygen. Saturated salt solution has about 2 mg/L oxygen in equilibrium with the atmosphere. It is a lot less than the 10 mg/L in pure water at room temperature, but far from the 0.5 mg/L mentioned in the question.
Article Dissolved oxygen concentrations in hypersaline waters
(See figure 1)
From my perspective, there's no direct bearing between PH of the Wastewater and it Dissolved Oxygen level so far, rather there's need to confirm the Conductivity, acidity and alkalinity levels of the wastewater, these can go a long way to determine the presence high concentrations of
salts that reduce the oxygen solubility to minimal. Bet a zero concentrations of DO in wastewater is dubious at extremes. Also check the fecal choliform levels information on this with little error in the measurements can prove your experiement results right.
pH is related to the presence of free carbon dioxide and not with DO.
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