Benzophenones(BPs) are a class of widely used UV filters, which have been frequently detected within multiple environmental matrices. Disinfection is a necessary process in water treatment processes. The transformation behaviors and toxicity changes of 14 BP-type UV filters during chlorination disinfection treatment were investigated in this study. A new index, the acute toxicity formation potential, was proposed to evaluate the toxicity changes and potential risks of BP-type UV filters during chlorination treatment. It was found that 13 of 14 BP-type UV filters exhibited toxicity decreases in the chlorination disinfection process, more or less, while one showed a toxicity increase. The toxicity changes were dependent on substitution effects, such that 2,4-di-hydroxylated or 3-hydroxylated BPs exhibited significant toxicity decreases after chlorination treatment due to the ready cleavage of the aromatic ring. Importantly, the acute toxicity changes could be duplicated in an ambient water matrix.
An assessment method based on three toxicity tests (algae growth inhibition,daphnia immobilization and larval fish toxicity) was used to screen the biological safety of reclaimed water which was reused as sole replenishment for scenic water system in a park (SOF Park) in northern China.A total of 24 water samples were collected from six sites of water system in the SOF Park in four different seasons.The results indicated that:(1) the reclaimed water directly discharged from a reclamation treatment plant near the SOF Park as influent of park had relatively low biological safety (all samples were ranked as C or D);(2) the biological safety of reclaimed water was improved greatly with the ecological reclamation treatment processes composing of artificial wetland system and followed oxidation pond system;(3) the biological safety of reclaimed water in the main lake of SOF Park kept at a health status during different seasons (all samples were ranked as A);(4) there was some certain correlation (R 2=0.5737) between the sum of toxicity scores and dissolved organic carbon for the studied water samples.It was concluded that the assessment method was reliable to screen the safety of reclaimed water reused as scenic water,and the reclaimed water with further ecological purification processes such as artificial wetland and oxidation pond system can be safely reused as scenic water in park.
The reclamation and reuse of wastewater is one of the possible ways to relieve the serious fresh water resource crisis in China. Efficient reclamation treatment technologies ensure the safe reuse of reclaimed water. In order to screen out and evaluate technologies appropriate for reclamation treatment, a great deal of efforts have been brought to bear. In the present study, a toxicity-based method including a Photobacterium phosphoreum test for acute toxicity and SOS/umu test for genotoxicity, accompanied by the traditional physicochemical parameters DOC (dissolved organic carbon) and UV 254 (absorbance at 254 nm), was used to measure the treatment performance of different reclamation processes, including the anaerobic-anoxic-oxic biological process (A2O) and subsequent physical/chemical reclamation processes (ultrafiltration, ozonation, chlorination). It was found that for the secondary effluent after the A2O process, both the toxicity and physicochemical indices had greatly decreased compared with those of the influent. However, chemical reclamation processes such as ozonation and chlorination could possibly raise toxicity levels again. Fortunately, the toxicity elevation could be avoided by optimizing the ozone dosage and using activated carbon after ozonation. It was noted that by increasing the ozone dosage to 10 mg/L and employing activated carbon with more than 10 min hydraulic retention time, toxicity elevation was controlled. Furthermore, it was shown that pre-ozonation before activated carbon and chlorination played an important role in removing organic compounds and reducing the toxicity formation potential. The toxicity test could serve as a valuable tool to evaluate the performance of reclamation processes.
