Ecotoxicological Effect Of THF On Freshwater, Wastewater, Activated Sludge As Well As Its Biodegradation

The cyclic aliphatic ether tetrahydrofuran is a volatile and highly flammable liquid with an ether-like odor and a pungent taste,easily soluble in both water and organic solvents.THF is an important medium solvent in chemical industry,e.g.as a reaction medium for Grignard and metal hydride reactions,and as a precursor in the synthesis of butyrolactone,succinic acid,and 1,4-butanediol diacetate.Furthermore,it is employed in the fabrication of articles for packaging, transporting,and storing of foods,as a solvent for dyes and lacquers,and as a chemical intermediate solvent in polymerization for fat oils,unvulcanized rubber,and reins.THF is also an indirect food additive when it is in contact with the surface of articles intended for use in food processing.THF is easy to volatilize and hard to be biodegraded.Little is known about the influence and fate of tetrahydrofuran in the environment.The aim of this thesis is to investigate the effects of THF on dissolved oxygen,pH,culturable microbes(bacteria,actinomycetes and fungi)and enzyme activities(dehydrogenase,protease,urease,catalase,phosphatase,amylase and lipase) respectively in fresh water(from the Tiesha river and the West lake),wastewater and activated sludge(from Sibao sewage plant in Hangzhou,China).Distilled water was used as the reference.The dissolved oxygen in distilled water fresh water(from the Tiesha river and the West lake) and wastewater(from Sibao sewage plant in Hangzhou,China)declined with addition of THF. However,the dissolved oxygen in activated sludge increased with increasing of THF concentration.The pH values in distilled water dropped obviously with increasing concentration of THF.However,the pH values in fresh water,wastewater and activated sludge rose up with increasing of THF concentration.The pH values in wastewater containing 0.00,0.06,0.25,0.49 0.74 and 0.99 mol·L^-1THF kept at similar level during incubation period from 0 d to 21st d.The pH values in samples with 0.00, 0.74 and 0.99 mol·L^-1THF declined with incubation time during period of 21st d to 35th d.The pH values of treatments with 0.25 and 0.49 mol·L^-1THF were rising from 0 d to the 42nd d.The pH values rose up in treatments with THF during period of the 35th to the 42nd d,but that of sample without THF reduced down to 6.51.The short-term influence of THF on pH in wastewater was not obvious in selected concentrations,but the long-term effect was significant.It can be concluded that influence of THF on pH in wastewater was not produced directly by THF itself,but via microbes affected by THF.Culturable fungi were sensitive to THF.CFU of culturable fungi at concentration of THF 0.06 mol·L^-1was higher than that of CK during the observation period except the 14th day.However, all were lower than that of CK when concentration of THF was 0.25,0.49,0.74 and 0.99 mol·L^-1, respectively.Effects of tetrahydrofuran on dissolved oxygen,pH,culturable microbes(bacteria, actinomycetes and fungi)and four kinds of selected enzymes(protease,phosphatase,amylase and lipase)were assayed in wastewater at the same time.The wastewater containing some activated sludge was taken from the aeration basin in Sibao sewage plant in Hangzhou,China.It was observed that lower concentration of THF enhanced aerobic respiration and higher concentration of THF decreased soluble oxygen content in wastewater.The short-term influence of THF on pH was not obvious,but the long-term effect was apparent.Inhibition of THF on culturable aerobic microbes rose up with increasing of THF concentration but decreased with elongation of incubation time.No obvious inhibition of THF concentration on activity of protease,phosphatase, amylase,and lipase was found.It can be concluded that lower concentrations of THF had no obvious influence on wastewater in urban sewage plant.Phosphatase activities in treatments with 0.74 and 0.99 mol·L^-1THF were significantly higher than in treatments with 0.00 and 0.06 mol·L^-1THF.Phosphatase activity decreased with incubation time that was very significantly higher on 0 day than on the 7thd,14th d,21st d,35th d,and 28th d. It seemed that THF could increase activity of phosphatase in wastewater.There was no significant difference among protease activities influenced by dose of THF(F= 2.09,P=0.1000),but there was by incubation time(F=46.79,P＜0.0001).Turkey's mean comparison for incubation time showed that protease activities were significantly higher on 0 d and 28th d than on the 14th d,21st d,7th d,and 35th d.It showed that THF had no obvious influence on activity of protease in wastewater.Population of culturable bacteria in wastewater was growing during period of the 28th and 35th d.It seemed that culturable aerobic bacteria in wastewater could utilize THF as carbon source. More assays are needed to be done to prove whether THF could be used by bacteria in wastewater or not.Effects of THF on the activities of dehydrogenase,protease,phosphatase,urease and catalase were investigated in activated sludge taken from the secondary sedimentation pool in the Sibao sewage plant in Hangzhou,China.It was observed that tetrahydrofuran could completely inhibit dehydrogenase activity during period of incubation time and over the range of selected concentrations.On the contrary,the protease activity was not inhibited by THF.Phosphatase, urease and catalase activities were strongly affected by THF and their activities descended with increasing concentration of THF.EC₁₀,EC₅₀,and EC₉₀of THF on phosphatase,urease and catalase activities were calculated according to the equation obtained from regression model of dose-effect curve.Master the effect of THF on the enzymes in activated sludge can help us to understand the influence and fate of THF in the environment,and help us to enrich pure cultures or activated sludge to biodegrad THF.Isolate QFF3 is able to grow on THF as a sole growth carbon substrate.Phylogenetic analysis indicates thatisolate QFF3 may be a new strain to biodegrade THF.The isolate QFF3 has been identified as Brevundimonas bullata QFF3,according to its shape,growth patterns and phylogenetic analysis.