Transportationand Distribution Of Typical Pharmaceutically Active Compounds In The Water Systemof City And Their Removal In Constructed Wetland System (CWS)

Pharmaceutically active compounds (PhACs) are widely used for the treatment ofbacterial diseases in humans, and some are applied to livestock and fish for diseaseprophylaxis and treatment or for growth promotion.Large amounts of PhACs and theirmetabolites are continuously released into environmental compartments such as rivers,lakes, even ground water and soil, because all kinds of drugs were misused seriously forlack of scientific direction. Thetransportation, transformation, ecological toxicology andcontrolof PhACs have therefore provoked considerably scientific attention around theworld over the past decade. However, only a few studies about the situation in Chinahave been reported. The Chongqing region is located at the confluence of YangtzeRiver and Jialing River, water quality of drinking water source influences the safety ofdrinking water of the middle and lower Yangtze River.During the past two decades,Chongqing has become one of the fastest growing economies and most denselyurbanized areas in the world, and pharmaceutical consumption of the region is large.However, there are no studies reporting the behavior and fate of PhACs in the aquaticenvironment of Chongqing.Therefore, the occurrence, behavior and environmental fateof PhACs in the aquatic environment of this regionwere studied using ahigh-performance liquid chromatography coupled to a tandem massspectrometer.Besides, we researched the behavior and removal mechanismPhACs in theconstructed wetland systems (CWS) which are the last defenses forPhACs entering intoenvironment. The results are as follows:The methods for determination of selected PhACs in the environmentA sensitiveanalyticalmethodwas developed fordeterminingthe selected PhACs(including several antibiotics, analgesics, antiepileptics, antilipidemics andantihypersensitives) in the water and sludge. The wastewater samples were extracted byOasis HLB cartridges (6mL,500mg),while the solid samples (sludge and suspendedsolid matter) were extracted by ultrasonic-assisted extraction with solvents followed byan enrichment and clean-up step with solid-phase extraction using HLB cartridges. Theextracted PhACs were analyzed using high-performanceliquidchromatography-electrospray ionization tandem massspectrometry(HPLC-MS/MS) with multiple reactions monitoring(MRM).The recoveries achieved forthe target PhACs ranged from66.4~114.9%for the river water, from62.5~133.2%for the influent, from64.5%~111.9%for the effluent, and from59.5%~139.2%for thesludge and their relative standard deviation was below16%. Limits of quantification(LOQs)(signal-to-noise ratio10) ranged from0.03ng/L to3.4ng/L for the surfacewater, from0.2ng/L to17.5ng/L for influent wastewater, from0.2ng/L to5.6ng/L foreffluent wastewater, and from0.17μg/kg to5.83μg/kg for sludge, respectively.Occurrence, transportation and ecotoxicological assessmentof the selectedPhACs in the aquatic environmentTwenty-one target PhACs from8therapeutic classes covering a wide range ofphysicochemical properties and biological activities, were analyzed at four full-scalewastewater treatment plants (WWTPs) in Chongqing. All the21analyzed PhACs weredetected in wastewater at concentrations ranging from low ng/L to a few μg/L.Of all21target PhACs,18were present in sludge and most PhACs were found at ng/g dw levels.Acetaminophen predominated in all analyzed influent samples at concentrations rangingbetween1.2-7.7μg/L, followed by sulfamethoxazole, azithromycin, roxithromycin andofloxacinThe elimination of PhACs except acetaminophen is incomplete,and carbamazepine,clofibric acid and metoprololshowed negative removal.Based on the mass balanceanalysis,biodegradation is believed to be the primary removal mechanism, and for mostof the selected pharmaceutical residues, the portion wasted with the treated sludge intothe environment was negligible. However, because all the target quinoloneantibioticscontain nitrogen as positively-charged moiety and azithromycin possessespositively charged dimethylamino group, quinolone antibiotics and azithromycin wouldhave high sorption potentials through electrostatic interactions between their positivelycharged locations and the negatively charged sludge.Here, based on measured pharmaceutical concentrations ininfluent of the WWTPand the pharmacokinetics of PhACs in humans,we created a back-calculatedmodel.Theback-calculation can supply more consumption information and,if necessary,can work as a reference for improving current statutoryregulation on pharmaceuticalconsumption.Based on the result of the risk assessment for the effluent, receiving water andsludge, the environment concentrations of single compounds (including sulfadiazine,sulfamethoxazole, ofloxacin, azithromycin and erythromycin-H2O) in effluent andsludge, as well as the mixture of the21detected PhACs in effluent, sludge andreceiving water had a significant ecotoxicological risk to algae. The concentration addition model was used to estimate the toxicity of the mixture of the21PhACs. Theoverall RQ(sum)for algae was more than unity in the effluent, receiving water and sludge.Thus, the mixture can lead to a high risk in the Chongqing water environment, whichmust not be ignored.Of all21target PhACs,14PhACs were detected in source water withazithromycinhaving the highest concentration (about20ng/L). Conventional watertreatment processes cannot remove these PhACscompletely, and there were some targetPhAC were detected in treated water,11in DWTP A and6DWTP B, respectively.Theobtained results showed that the individual treatment steps in the DWTPs mostmarkedly contributing to removal of most target substances were sand filtration, and theremoval of most PhACs in the disinfection processes was negligible.The removal of PhACs in CWSThesorption capacity of four frequently-used support medium (zeolite, gravel,LightExpandedClayAggregate(LECA)andquartz sand) weighed against selectedpharmaceuticals (metropolol, carbamazepine, clofibric acid, sulfamethoxazole,norfloxacin)was measured, and their physical, chemical andmineralogicalcharacterization waspursued. Gathering the information from these approaches helpedin selecting adsorbent materials for CWs—LECA. Then we built the CWS and studiedthe removal efficiencies of the selected PhACs (SMZ, OFX, ROX and CBZ) in theCWS, and the response of microbes and microphytes to the PhACs exposure in CWS atlow concentrations. Results illustrated that the CWS can effectively remove the PhACsand the removal effect of the selected PhACs in the our CWS were higher than thetraditional WWTPs. At different pharmaceutical concentration levels (0~500μg/L), thesuperoxide dismutase (SOD), catalase (CAT) and peroxidase (POD) are mutuallyinteractive to remove the reactive oxygen species (ROS), and the photosynthesis of theplant was influenced, but the influence was weakened as time went by and the plantgrowth was not influenced eventually.Furtherinvestigationswereconductedusingphospholipidfattyacids(PLFAs)profilestofollowtheresponseofthe soilmicrobial communitywiththepurposetoillustratethe removal mechanismof PhACs in theCWS. The functional bacteria in different CWS were not changed but their orderindifferent treatment was altered. In comparison with the control (Planted (0)), some newPLFAs were found in the CWS at the concentrations of PhACsranging from10μg/L to500μg/L. The soil enzyme activities (catalase,urease and dehydrogenase activity) were promoted at concentrationsof the target PhACs between10μg/Land30μg/L, and werenot inhibited with the target pharmaceutical concentrations ranging from100μg/L to500μg/L.