Application of heat shock protein assay and proteome assay to water from wastewater treatment plant

Assessment of organic micropollutants occurrence in treated wastewater using heat shock protein 47 stress responses in Chinese hamster ovary cells and GC/MS-based non-target screening

Combining bioassays and analytical chemistry screening is a powerful approach to assess organic micropollutants which are the main contributors to toxic potential in complex mixtures of treated wastewater (TWW). The aim of this study was to perform a comprehensive toxicity assessment of treated effluents using stress response bioassays and then to assess the occurrence of the organic micropollutants which were responsible for this biological response using gas chromatography coupled with a mass spectrometry detector (GC/MS). Results showed that TWW samples induced significant stress response on Chinese hamster ovary cells, stably transfected with heat shock protein 47 promoter, at 0.1%, 1%, 5% and 10% concentrations. The organic chemical compounds responsible for stress response potential were identified at different percentage values using non-target chemical screening. Of the compounds detected in TWW1 and TWW4, 55.09% and 74.5% respectively, fell within the class of aliphatic hydrocarbons. Aliphatic hydrocarbons were also present in TWW3 at 26.46% whereas 11.96% corresponded to 6-acetyl-1,1,2,4,4,7-hexamethyltetralin and 16.08% to triethoxysilane. Moreover, 76.73% of TWW2 was recorded as decamethylcyclopentasiloxane (D5) and 17.44% as n-hexadecanoic acid.

Heat shock protein 47 stress responses in Chinese hamster ovary cells exposed to raw and reclaimed wastewater

As wastewater reclamation and reuse becomes more widespread, risks of exposure to treated wastewater increase. Moreover, an unlimited number of pollutants can be identified in wastewater. Therefore, comprehensive toxicity assessment of treated wastewater is imperative. The objective of this study was to perform a comprehensive toxicity assessment of wastewater treatment systems using stress response bioassays. This powerful tool can comprehensively assess the toxicity of contaminants. In this study, samples from conventional activated sludge treatment, membrane bioreactors (MBRs) with different pore sizes and sludge retention times (SRTs), rapid sand filtration, coagulation, nano-filtration (NF) and reverse osmosis (RO) were investigated. The results of stress response bioassays confirmed that the secondary effluent showed higher stress response than influent indicating that biological treatment generates toxic compounds. The results obtained from molecular weight fractionation of water samples demonstrated that organic matter with a higher molecular weight fraction (>0.1 μm) causes toxicity in secondary effluent. Furthermore, supernatant from MBR reactors showed toxicity regardless of SRT. On the other hand, stress response was not detected in MBR permeates except for an MBR equipped with a larger pore size membrane (0.4 μm) and with a short SRT (12 days). While rapid sand filtration could not remove the toxic compounds found in secondary effluent, coagulation tests, operated at an appropriate pH, were effective for reducing stress response in the secondary effluent. Experimental findings also showed that stress response was not detected in cases of NF and RO permeate subsequent to MBR treatment.

Adaptations in microbiological populations exposed to dinitrophenol and other chemical stressors

Microbiological populations in natural and engineered systems may experience multiple exposures to chemical stressors, which may affect system functions. The impact of such exposures on the metabolism of a population of Pseudomonas aeruginosa was studied using respirometry. Two serial exposures to low concentrations of 2,4-dinitrophenol (DNP), pentachlorophenol (PCP), or N-ethyl maleimide (NEM) did not affect metabolism beyond that expected for a single exposure. However, at higher concentrations, three exposures to DNP led to a combination of metabolic stress and resilience in the population. At a low DNP concentration of 400 mg/L, multiple exposures led to increased stress but indicated no development of resilience. At a high DNP concentration of 1,200 mg/L, no biological activity was observed, indicating that the population did not survive the exposure. At intermediate concentrations of 800 and 900 mg/L DNP, stress was observed, but it was found to decrease after multiple exposures. This, combined with the observation that the size of the population decreased, indicated that resilience in the population had developed because of elimination of the weaker organisms in the population. In contrast, the lack of resilience at the lower DNP concentration was attributed to the survival of the strong as well as weak members, lowering the resilience of the population as a whole. The development of resilience within a window of stressor concentrations is an important finding with implications for predicting the performance of biotreatment processes and biosensor technologies and for interpreting ecotoxicity risk assessments.