Dissolved oxygen analysis in hydrodynamic cavitation pre-treatment for enhanced biological decomposition of sedimented municipal wastewater

Municipal wastewater treatment plants in developing countries frequently experience ineffective performance due to inadequate treatment facilities. This leads to significant environmental pollution from untreated or partially treated wastewater discharge. This study addresses this challenge by introducing a novel method for pre-treatment sedimented wastewater by combining hydrodynamic cavitation with Dudar brown coal or zeolite as adsorbents. The rationale for combining HC and adsorption lies in their potential synergistic effect: HC promotes the disintegration of particulate matter and cell lysis, increasing the solubilization of organic compounds and improving oxygen transfer, while adsorption facilitates the removal of slowly biodegradable and soluble organic substances. Together, these mechanisms can improve overall biodegradability and organic load reduction. The objective of this research is to enhance the efficiency of aerobic biological degradation by increasing the dissolved oxygen concentration in municipal wastewater treatment after primary sedimentation. The change in dissolved oxygen (DO) concentration during hydrodynamic cavitation and its relationship with other parameters, such as temperature, soluble chemical oxygen demand (SCOD), total organic carbon (TOC), and biological oxygen demand (BOD 5 ), were measured and analyzed. Experiments were conducted using a hydrodynamic cavitation setup with a 1.86 m 3 open storage tank, with or without 0.5% adsorbents dosage, operating for 24 min, at a temperature 23 ° C with samples taken at 0, 4, 8, 16, and 24-min intervals. The results showed that the DO concentration due to cavitation increased in the initial retention time from 4.5 mg/L to 8 mg/L until 4th minute of retention time, indicating aerobic degradation was taking place. Between 8 and 16th minutes of treatment, BOD 5 increased because of the dissolution of organic substances. Finally, at the end of the treatment, BOD 5 declined, while DO stagnated between 7.02 and 7.86 mg/L demonstrating secondary aerobic degradation. The TOC removal efficiency data showed that hydrodynamic cavitation with Dudar brown coal addition reached the highest TOC removal efficiency of 74.16%.