Tephra subsoil (allophanic) columns are used to determine the soil phosphorus (P) sorption capacity to remove P from dairy industry wastewater (pH = 8, with high sulfate concentration). The effluents collected had shown coloration - pale yellow to intense yellow although the influent was colorless. Could it be due to the presence of iron or silicate or can there be other reasons?
You ned to study physicochemical parameters like pH (for both effluent and influent) temp, color, DO, BOD, COD, TDS, TSS, TS, Chloride Sulphate, Oil & grease also. to understand cause of coloration. As you using allophanic filters, which helps to reduce the coloration of iron containing waste water. I guess, Iron is not the cause.
Please consider checking pH of the effluent and influence. But as you said, Iron could be the reason behind the coloration. I suggest you add air or some other oxidizing agent to your waste water source if you have not done it yet.
This issue should be minimized with the oxidation process.
Dairy Industry Wastewater Treatment - With Phosphorous
Pretreatment of effluents consists of screening, flow equalization, neutralization, and air flotation (to remove fats and solids); it is normally followed by biological treatment. If space is available, land treatment or pond systems are potential treatment methods. Other possible biological treatment systems include trickling filters, rotating biological contactors, and activated sludge treatment. -
Various physicochemical techniques have been studied for their applicability in treatment of wastewaters . Like sedimentation, screening, aeration, filtration, flotation, degassification, chlorination, ozonation, neutralization, coagulation, sorption, ion exchange, etc. Several limitations of physicochemical methods including partial treatment, higher cost, generation of secondary pollutants, higher quantity solids and use of chemicals agents make the biological methods a favorable alternative for the removal of pollutants. Waste materials associated with the food industry including the wastes generated by the dairy industry namely sludge, heavy organic matter, fats, oil & grease, fatty acids, nitrogenous compounds are notables. Dairy wastewater deserves special attention since its levels of potential contaminants typically exceed those levels considered hazardous for domestic waste-water. May, what is the concentration of Sulphate? It will make me understand the situation at site, then I may be of some help.