Abstract
In the present work, electrochemical technology was used simultaneously for the deactivation of microorganisms and the destruction of micro-pollutants contained in synthetic urine wastewaters. Microorganisms (E. coli) were added to synthetic urine wastewaters to mimic secondary treated sewage wastewaters. Different anode materials were employed including boron-doped diamond (BDD), dimensionally stable anode (DSA: IrO2 and RuO2) and platinum (Pt). The results showed that for the different anode materials, a complete deactivation of E. coli microorganisms at low applied electric charge (1.34 Ah dm−3) was obtained. The complete deactivation of microorganisms in wastewater seems to be directly related to active chlorine and oxygen species electrochemically produced at the surface of the anode material. Complete depletion of COD and TOC can be attained during electrolyses with BDD anode after the consumption of specific electric charges of 4.0 and 8.0 Ah dm−3, respectively. Higher specific electric charges (>25 Ah dm−3) were consumed to removal completely COD and about 75% of TOC during electrolyses with DSA anodes (IrO2 and RuO2). However, the electrolysis using Pt anode can partially remove and even after the consumption of high specific electric charges (>40 Ah dm−3) COD and TOC did not exceed 50 and 25%, respectively. Active chlorine species including hypochlorite ions and chloramines formed during electrolysis contribute not only to deactivate microorganisms but also to degrade organics compounds. High conversion yields of organic nitrogen into nitrates and ammonium were achieved during electrolysis BDD and DSA anodes. The results have confirmed that BDD anode is more efficient than with IrO2, RuO2 and Pt electrodes in terms of COD and TOC removals. However, higher amounts of perchlorates were measured at the end of the electrolysis using BDD anode.
Highlights
Human urine represents a small volume of domestic wastewater but it is one of the main sources of water pollution
It is important to investigate the electrochemical treatment of synthetic urine wastewaters in presence of E. coli as pathogenic microorganisms targeting the transformation of organic content into less harmful compounds and the disinfection of the treated wasters to deactivate the microorganisms
Complete depletion of chemical oxygen demand (COD) and total organic carbon (TOC) can be obtained during electrolyses with boron-doped diamond (BDD) anode at applied (BDD), dimensionally stable anode (DSA: IrO2 and RuO2) and platinum (Pt) electrode materials electric charge of 4 Ah dm−3 and 8 Ah dm−3, respectively
Summary
Human urine represents a small volume of domestic wastewater but it is one of the main sources of water pollution. Urine is characterized by a very complex chemical composition including both ionic and molecular compounds. Several researchers have investigated the composition of human urine [1,2]. The organic fraction of urine is composed principally of urea, uric acid and creatinine. It contains most of the essential nutrients nitrogen, phosphorus and potassium and very low metals content [1,3,4]. Certain hormones and medicinal residues are excreted with the urine, which find themselves in the sewers and it has been considered as an emerging environmental problem [5]. Heinonen-Tanski et al [2] reported that a possible transmission of pathogens could result from the reuse of inadequately treated human and animal wastes in irrigation
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