Usage of Low-Cost Bio Electro Technology to Convert Class B Biosolids Processes (aerobic and anaerobic digestion) to Class A Disinfected and Stabilized Biosolids

摘要

Novel BioElectro process uses enhanced electrokinetic phenomena to produce exothermic reactions for pathogens inactivation. The technology was demonstrated to achieve various levels of disinfection of biosolids. Pasteurization and even sterilization of anaerobically digested biosolids were demonstrated. The research showed reduction of Clostridium perfringens spores by 8 log within less than two hours, while 3 log reduction was reached within less an hour. Simultaneously, properties of the biosolids were changed leading to improved dewatering. The new process is ready for full scale application. One application can be for pre-treatment before ambient temperature aerobic digestion which disinfects the solids and facilitates thermophilic digestion, thus generating a Class A finished product. The cost of ensuring that aerobically-digested solids meet Class A standards is often prohibitive-particularly at small to mid-size facilities where there is a limited resale market. Subsequently, many municipalities are searching for alternative technologies that are efficient and cost-effective. The BioElectro process provides a potential solution to more energy intensive options, since it generates exothermic reactions in biosolids containing ammonia due to combination of a low voltage DC field with additives. Preliminary studies have shown that temperature could rise to 50 ℃ and 70 ℃ within less than half an hour to an hour, respectively, using BioxyS™ and a voltage gradient below 5 V/cm. The heat generated in the BioElectro process facilitates subsequent thermophilic digestion-decreasing the time needed for biosolids stabilization and ensuring biosolids disinfection. BioElectro provides the potential to retrofit existing aerobic digesters to achieve a Class A biosolids through disinfection and thermophilic digestion, without increasing the existing digestion volume. Bench-scale studies have shown that the process would require small batch or continuous flow tank (due to short retention time) prior to existing digesters, with a system of electrodes supplied with a low DC voltage gradient. The existing WAS feed can be diverted prior to digestion or a portion of existing digesters can be utilized. The process can be cost effective for smaller utilities because of the low construction costs, the potential to reduce existing digester volumes, and changes to sludge properties that improve dewatering and reduce operational costs. This technology was reviewed through the LIFT Technology Scan program and received favorable comments.