Electrochemical treatment for cleaner hospital wastewater
Current approaches to the treatment of hospital wastewater include biological treatment, but this cannot degrade persistent contaminants. Alternatives such as reverse osmosis membranes are highly energy intensive and chemical oxidation processes require high doses of chemicals. The aim of the project ELECTRO HOSPITAL (Next-generation electrochemical technology for the treatment of hospital wastewater: electrogenerated sulphate radicals for complete destruction of persistent pollutants) was to investigate the performance of electrochemical oxidation for the treatment of hospital wastewater. In recent years an innovative oxidation technology based on the generation of the sulphate radical (SO4-) a strong oxidant, and hydroxyl radicals has attracted a lot of interest for wastewater treatment. Sulphate radicals are known for their high selectivity for the oxidation of contaminants. Therefore, ELECTRO HOSPITAL formed highly oxidising sulphate and hydroxyl radicals by applying current to an anode at atmospheric temperature and pressure. Results showed that, besides sulphate radicals, sulphate ions were also oxidised to persulphate, which was further activated at the anode surface and may contribute to the oxidation and mineralisation of organics. The formation of sulphate based oxidants was confirmed by clarifying the mechanisms underlying the oxidation of iopromide and diatrizoate, X-ray agents typically found in hospital waste water. It was also found that the presence of sulphate ions decreases the detrimental effect of chloride and formation of toxic organochlorine byproducts. ELECTRO HOSPITAL results are highly relevant to the real life application of electrochemical treatment, since formation of chlorinated byproducts is one of its main limitations. The projects results indicate that this can be significantly reduced by increasing the amount of sulphate. The sulphate can then be separated out following anodic oxidation using electrodialysis, to avoid issues with increased sulphate concentration in the waste water. Although ELECTRO HOSPITAL was developed to combat contamination in hospital wastewater it also has implications for the treatment of sulphate-containing waters, such as from fermentation industries. The technology developed may also be applied as an alternative to in situ chemical oxidation (ISCO) treatment of contaminated groundwater. ELECTRO HOSPITAL has several important advantages to existing oxidation technologies as it does not generate secondary pollution, has no pH limitations and does not require any external activators, such as iron. Thus, the technology will provide project a novel, clean option for hospital wastewater remediation that is also applicable to the treatment of other forms of contaminated water.
Keywords
Hospitals, wastewater, ELECTRO HOSPITAL, sulphate radicals, electrochemical oxidation, hydroxyl radical, persulphate, organochlorine, electrodialysis, in situ chemical oxidation