الملخص الإنجليزي
Wastewater from fish processing industries is a significant source of environmental pollution, a biohazard to humans and other living organisms. Wastewater produced by fish processing plants contains a variety of pollutants in soluble, colloidal, and particle forms. To address this issue, several researchers have explored different methods for the treatment of fish wastewater. In this study, chemical coagulation of aluminum sulfate, ferric sulfate and flocculation of high-density with different charges polyacrylamide at different pH were used for the fish wastewater treatment. In addition, sewage sludge was used as a natural adsorbent. The treated sludge was used to produce activated carbon. The prepared activated carbon was then tested for the removal of heavy metals such as lead (Pb2) from the aqueous solution. Notably, this study distinguishes itself by utilizing polyacrylamide flocculants of varying densities and by employing sewage sludge as a natural adsorbent.
The treatment using aluminum sulfate (Al2(SO4)3) reduced the turbidity and color by 90% and 92% respectively with dosage of 200 ppm at pH-7. The Chemical Oxygen Demand (COD) was reduced by 16%. The treatment with ferric sulfate (Fe2(SO4)3) reduced turbidity by 80% (at pH=7) and color by 93% (at pH=5) with a dosage of 200 ppm. The COD was reduced by 29%. The findings demonstrate that within the first 30 minutes of treatment, the negative and positive polyacrylamide decreased turbidity by 88% and color by 92% with all concentrations at pH-5. The COD decreased by 36%. During all tests, there was no change in BOD except for treatment at pH=5, the Biochemical Oxygen Demand (BOD) was reduced by 30% due to the addition of H2SO4 for adjusting the pH value. The negative electric charges (zeta potential) of the fish wastewater had little changes, despite the use of treating chemicals with positive charges due to the high negative charge intensity of the wastewater. The conductivity of the treated wastewater was raised by 41% due to the addition of the mineral
salts solution for treatment.
The rheological tests on residual solid after treatment with chemicals and polyacrylamide showed non-Newtonian fluid behavior. The shear rate correlations of all residual materials follow the Bingham model with low yield stress and low limited viscosity. These results indicate that these residual materials would cause less friction during pumping and transportation. The results of using sewage sludge natural adsorbent for removing turbidity and color showed a reduction of more than 96% and 91% respectively.
The prepared activated carbon from treated and untreated sewage sludge showed acceptable efficiencies for metal adsorption, similar to that of commercial activated carbon 60%. The prepared activated carbon from treated sewage sludge with wastewater gave slightly better adsorption efficiency. FT-IR, SEM, XRD, and EDS were used for the characterization of prepared activated carbon.
The factorial design of experiments was used to determine the most influential factors in removing turbidity and COD from fish processing wastewater using chemical coagulation. According to the Pareto charts, the parameters coagulant dosage, duration, and pH have different effects on COD and turbidity removal, as well as the relationships between them. None of the factors influence COD removal by positive polyacrylamides or high positive
polyacrylamides.
