Abstract
Biological processes are the most widespread methods for wastewater treatment. However, they are limited in their ability to degrade toxic and refractory pollutants, contaminants that electrochemical processes can remove. Therefore, this research explored the possibility of treating sewage by an anaerobic biological process followed by an aerobic system integrated to an electrolytic process. Three sequential batch reactors were operated in an automated way. Each of three reactors represented a process: aerobic biological treatment (BR); electrolytic treatment (ER); and a combination of both, the bio electrolytic reactor (BER). Two phases were ran with different electrodes: (Phase 1) stainless steel and (Phase 2) graphite. The electric current was varied from 0.001 to 0.100 A. COD, TS, SS, turbidity, and the zooplankton community were monitored. The highest organic matter removal efficiencies were 86%, 79% and 87% for BR, ER and BER, respectively. The best weekly BER efficiencies for COD removal were 90% and 98%, with current densities of 0.27 A/m2 (Phase 1) and 0.05 A/m2 (Phase 2). The main conclusions about bio electrolytic process were: (1) it did not achieve organic matter removal high enough to justify its application; (2) inert electrodes are the more indicated; and (3) the zooplankton community was affected by the electric current.
Highlights
The most-used processes for sewage treatment are biological treatments
It was noticed that the bio electrolytic reactor (BER) best performance in the first phase was reached on the second week of operation, while in the second phase the best performance occurred in the first week
This suggests that the effluent from the electrolytic treatment (ER) and BER reactors contained only Fe3+, which does not interfere in the COD test because these cations are in their maximum oxidation state
Summary
The most-used processes for sewage treatment are biological treatments. Biological methods give low degradation efficiency in the treatment of highly concentrated and biorefractory pollutants, especially certain industrial wastewaters containing toxic components such as pesticides, because the activity of microorganisms is inhibited by toxicity. To treat this kind of wastewater, many physical and chemical methods have been introduced (Liu et al, 2010). There is a global trend to improve existing sewage treatment processes and continuously enhance the quality of treated effluents, with the purpose of adapting them to environmental requirements and water reuse
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