Mutagenicity assessment of produced water during photoelectrocatalytic degradation

Abstract

Oilfield produced water was treated by photocatalysis, electro‐oxidation, and photoelectrocatalysis, respectively. The chemical composition and toxicity of the raw effluent and treated products were assessed by chemical and mutagenicity analysis. The raw effluent exhibited mutagenic activity in both strains of Salmonella typhimurium. The lowest concentration of the dichloromethane extract capable of inducing a positive response in strains TA98 and TA100 were as low as 4 and 5 μg/plate, respectively. All three technologies could detoxify direct‐acting mutagenic organic pollutants efficiently, although they could not completely eliminate mutagenicity in the water after 60 min of treatment. At equivalent doses, photoelectrocatalysis exhibited the greatest capability to reduce genotoxicity, whereas photocatalysis was the least effective and did not cause appreciable change in mutagenicity. The gas chromatography—mass spectrometry (GC‐MS) analysis revealed that n‐alkanes (259.4 ng/L) and phenolic compounds (2,501.4 ng/L) were the main organic constituents in the oilfield produced water. Thus, the results of both biological and chemical analysis indicate that photoelectocatalysis was the most effective technology for degradation of oilfield wastewater.

Review of technologies for oil and gas produced water treatment

“…Li et al [71] found that the COD removal efficiency of produced water by photoelectrocatalytic process was much higher than that of by photocatalytic or electrochemical oxidation. Li et al [72] also compared treatment of produced water by photocatalysis, electro-oxidation, and photoelectrocatalysis. Results showed that at equivalent doses, photoelectrocatalysis exhibited the greatest capability to reduce genotoxicity, whereas photocatalysis was the least effective and did not cause appreciable change in mutagenicity, but results of both biological and chemical analysis indicated that photoelectocatalysis was the most effective technology for degradation of oilfield wastewater.…”

Comparative study on the photoelectrocatalytic inactivation of Escherichia coli K-12 and its mutant Escherichia coli BW25113 using TiO2 nanotubes as a photoanode

“…This is because they only played a role for charge transport in solution during a PEC process rather than the active reactants involved in bactericide generation. Nevertheless, the presence of 0.2 M NaCl significantly increased the PEC inactivation efficiencies for both strains, and complete inactivation was achieved within 6 s. This is primarily due to that NaCl is well-known active electrolyte to accelerate the degradation of various organics during PEC process [39][40][41][42], although its application in bacterial inactivation is very limited [5]. Therefore, the enhancement mechanism of bacterial inactivation and inactivation kinetics response to different strains deserves a further investigation in the PEC system with NaCl as electrolyte compared with the PC system.…”

Photocatalytic degradation and detoxification of o-chloroaniline in the gas phase: Mechanistic consideration and mutagenicity assessment of its decomposed gaseous intermediate mixture

“…Four different dose groups (4000, 2000, 1000, and 500 g plate −1 ) with the same level as the SOS/umu assay were set up for each sample too. The detailed test procedure and accounting methods for the Ames test were described in our previously published work [30].…”