Degradation of organic pollutants and characteristics of activated sludge in an anaerobic/anoxic/oxic reactor treating chemical industrial wastewater

Abstract

-A laboratory-scale anaerobic/anoxic/oxic system operated at the hydraulic retention times (HRT) of 20, 40, and 60 h with mixed liquor suspended solids (MLSS) concentrations of 3 g/L and 6 g/L was considered for treating chemical industrial wastewater rich in complex organic compounds and total dissolved solids. Extending the HRT and increasing the MLSS concentration resulted in higher removal efficiency for chemical oxygen demand at 72%. Organic compounds in wastewater could be classified into easily-removed and refractory compounds during treatment. The easily-removed compounds consisted primarily of ethers, alcohols, and aldehydes, whereas the refractory compounds included mainly oxygen-containing heterocyclic and benzene-containing compounds. Results from energy-dispersive X-ray spectroscopy showed that several metal ions accumulated in activated sludge, particularly Fe(III). Fe accumulated mainly on the surface of sludge floc pellets and resulted in the compactness of activated sludge, which caused the values of mixed liquor volatile suspended solids /MLSS and sludge volume index to decrease.

Discussion of “Wastewater Effect on the Deposition of Cohesive Sediment” by Milad Khastar-Boroujeni, Kazem Esmaili, Hossein Samadi-Boroujeni, and Alinaghi Ziaei

“…It has been shown in numerous papers that the presentation of the results of laboratory analysis of the soil, sediment, or any material added to the soil is necessary because this information makes it easy to interpret the results and understandable for the reader (Mousavi et al 2017b(Mousavi et al , 2018Karlsson et al 2016). On the other hand, the biological properties of wastewater are equally important if not more so because the biological properties of wastewater significantly affect the breakdown and settling of the sediment (Wang et al 2014). Therefore, the biological effect needs to be discussed.…”