Curbing per- and polyfluoroalkyl substances (PFASs): First investigation in a constructed wetland-microbial fuel cell system.

The presence of per- and polyfluoroalkyl substances (PFASs) in water environments has been linked to a slew of negative health effects in both animals and humans, but the green and eco-sustainable removal technologies remain largely unknown. Constructed wetland coupled microbial fuel cell (CW-MFC) is termed a "green process" to control pollutants and recover energy. However, so far, no study has investigated the removal of PFASs and their effects on the performance of the CW-MFC systems. Here, we investigated the removal performance of PFOA and PFOS in the CW-MFC systems both in the absence and presence of electricity circuit, and explored the distribution and fate of PFASs and their interactions with other elements in the systems. Our findings demonstrated excellent removal efficiency of >96% PFOA and PFOS in CW-MFC systems. PFOA and PFOS were distributed throughout the system via wastewater flow, while electrode material and plants are the main enrichment sites in which MFC enhanced up to 10% PFASs removal. However, a loss of 7.2-13.5% of nitrogen removal and a decrease of 7.3% in bioelectricity output were observed when PFASs were introduced in the system. The driven force led to the loss of nitrogen removal and bioelectricity generation lies in the accumulation of PFASs in system composition, which affected microbial activity and community composition, damaging the health of the plant, and in turn reducing CW-MFC's functioning. No doubt, CW-MFC systems provide an alternative technique for PFASs removal, alleviating some limitations to the physical and chemical techniques, but further investigation is highly needed.

A review on antibiotics removal: Leveraging the combination of grey and green techniques.

Antibiotics are currently a major source of concern around the world due to the serious risks posed to human health and the environment. The performance of the secondary wastewater treatment processes/technologies (representing grey process) and constructed wetlands (CWs) (typical green process) in removing antibiotics and antibiotic resistance genes (ARG) was reviewed. The result showed that the grey process mainly removes antibiotics, but does not significantly remove ARG, and some processes may even cause ARG enrichment. The overall treatment in CWs is better than WWTPs, especially for ARG. Vertical subsurface flow CWs (VFCWs) are more conductive to antibiotics removal, while horizontal subsurface flow CWs (HFCWs) have a better ARG removal. More importantly, this review admits and suggests that the combination of grey process with green process is an effective strategy to remove antibiotics and ARG. The most advantage of the combination lies in realizing complementary advantages, i.e. the grey process as the primary treatment while CWs as the polishing stage. The efficiency of such the hybrid system is much higher than either single treatment process.

[Effects of Joint-reaction Combined by Ozonation and Coagulation on Aquatic Organic Matters].

Variations of residual ozone concentration in pure water and Al2(SO4)3 solution were studied. The spectral characteristics, contents of organic compounds and disinfection by products (DBPs) yields in preozonated, preozonated coagulated (POC) and ozonated combined coagulated (OC) waters were detected by differential absorbance(DA), three dimensional fluorescence excitation-emission matrix spectroscopy (3D-EEM), GC and TOC. The purpose of the work was to investigate the effects of ozonation combined with coagulation on their oxidation extents of organic matter and the production of DBPs. Studies showed that there were remarkable differences between the two processes, POC and OC, which proved the existence of joint interaction of ozone and coagulant. The joint interaction involved the following aspects. 1 Decomposition rate of ozone was improved; and the free radical production was increased during OC compared with POC. Comparing to ozone alone, 15.2% and 23.9% more radical capture with ozone 2mg·L-1, Al3+ 1 mg·L-1, 3 mg·L-1 were detected. 2 The difference of OC and POC was found in that organic matter removal of OC was lower than that of POC. The pathways of OC and POC showed difference, which resulted in differences of reaction between organic matter and disinfectant, as well as yields of DBPs. OC removed UV254 and DOC more efficiently than single ozonation or single coagulation; but less efficiently than POC. DCAAFP (Dichloroacetic acid formation potential) and TCAAFP (Trichloroacetic acid formation potential) were 47 µg·L-1 and 20.5 µg·L-1 respectively after treatment by POC with O3 1mg·L-1and Al3+1mg·L-1, and chloroform formation potential (CFFP) was 97.8 µg·L-1, which were 51%, 64.6% and 41.5% respectively lower than those in the raw water. Under the same dose conditions, DCAAFP, TCAAFP and CFFP after OC were 48.4 µg·L-1, 21.4 µg·L-1 and 117.3 µg·L-1, respectively, which were 49.6%, 63% and 29.5% lower than those in raw water. The difference between the efficiencies of POC and OC would be enlarged with increase of coagulant dose under the same ozone dose. Considering its safety and efficiency, the ozone dosage, adding spot and coagulant species must be taken into account when combined treatment of preozonation and coagulation is used; further investigations are also needed.