Research On Removal And Inactivation Of Cryptosporidium In Water By Conventional Water Purification Process And Ultrasonic-ozone Method

The microbiological risk of drinking water is an important issue for the water supply industry,Cryptosporidium is a widely distributed source of pathogenic protozoa.It can cause human-induced fever,vomiting,diarrhea and other symptoms,especially for patients with low immunity.Cryptosporidium has strong resistance to environmental change and traditional chlorine disinfectant,Traditional water purification process is difficult to completely remove Cryptosporidium in water,and once into the urban water supply system,it is easy to cause serious public health risks.Therefore,it is important to study the inoculation,removal and detection of Cryptosporidium in water supply.In this paper,we first examined the removal of Cryptosporidium by conventional water purification technology,followed by the study of the effect of ultrasonic synergistic ozone inactivation of Cryptosporidium and its influencing factors.Finally,aiming at the problem of time consuming and low accuracy of pathogen microbial activity detection,A method of RT-qPCR(reverse transcription-quantitative polymerase chain reaction)was used to detect the inactivation effect of pathogenic microbes.The removal efficiency and influencing factors of two conventional water purification processes by coagulation sedimentation and filtration were studied under laboratory conditions.By coagulation sedimentation,filtration,coagulation and filtration combined with removal of Cryptosporidium,and explore the coagulant,pH,hydraulic conditions,the thickness of filter and the influence of CODMn,the removal rate of turbidity and the removal rate of Cryptosporidium.The results showed that within a certain range,with the increase of pH,the survival rate of Cryptosporidium first decreased and then increased,pH value in the range of 8.0-9.0,Cryptosporidium removal rate reached the best;The removal rate of Cryptosporidium increased with the increase of PAC(0-10.0 mg/L)firstly and then decreased.When the dosage of coagulant was in the range of 4-6.0 mg/L,the removal efficiency of Cryptosporidium was the best;Turbidity can be used as indicator of removal rate of Cryptosporidium in water;Cryptosporidium removal rate increases with the media thickness corresponding increase;Coagulation and filtration combined with the removal of Cryptosporidium up to 99%.The effects of ultrasound and ozone on the inoculation of Cryptosporidium in water were investigated.The results were compared with the results of ultrasonic and ozone inactivation alone.The results showed that the inactivation rate of Cryptosporidium under ultrasonic and ozone coupling was higher than that of ozone and first ozone after ultrasound,And the coupling effect of ultrasound and ozone will produce synergistic effect;On the basis of this,the influence of the factors such as ozone dosage,ultrasonic frequency,ultrasonic power,temperature,pH value,turbidity,organic concentration and common ions in water on the Cryptosporidium.The results showed that,within a certain range,the inoculation rate of Cryptosporidium increased with the increase of ozone ventilation;When the ultrasonic power was 30W-150W,the inactivation rate increased with the increase of ultrasonic power;The inactivation rate of ultrasound frequency in low frequency region(20kHz-60kHz)was higher than that in high frequency region(200kHz-800kHz);When the water temperature was in the range of 5-35 ℃,the inactivation rate of Cryptosporidium increased first and then decreased;When pH was in the range of 5.5-9.4,the inoculation rate of Cryptosporidium increased with the increase of pH;High turbidity and high concentration of organic matter are not conducive to the promotion of Cryptosporidium inactivation rate;A small amount of two valence metal ions Ca2+ and Cu2+ in water is helpful to improve the fire rate of Cryptosporidium,N03-of Cryptosporidium inactivation has certain stimulative effect,SO42-of Cryptosporidium inactivation had almost no effect,HC03-of Cryptosporidium inactivation inhibition.The mechanism of ultrasonic-coupled ozone inactivation of Cryptosporidium in water was studied by studying the decomposition of ozone in water under the action of ultrasonic-coupled ozone,the effects of free radicals,scanning electron microscopy and protein experiments.The results showed that under the action of ultrasonic,the decomposition rate of ozone in water was greatly enhanced,and the decomposition of ozone was promoted to produce more OH,and the inactivation rate was enhanced.Under ultrasonic coupling,the cavitation of ultrasonic and the oxidation of free radical,Cryptosporidium cell structure has been severely damaged.Based on the expression of heat shock-induced hsp70 mRNA,a reverse transcription quantitative polymerase chain reaction(RT-qPCR)assay method was established to assess the inactivation of pathogenic microorganisms in water.With escherichia coli as experimental objects,the copy numbers of hsp70 mRNA was quantified by RT-qPCR method after heat shock induced,the effect of inactivation was evaluated by comparing the copy numbers of chloraminated sample and control sample.The results shows that the best condition for expression of hsp70 mRNA were heat shock induced at 42℃for 60 min;the sensitivity of detection was 900 cfu/ml;for the detection of chloramine inactivation,the inactivation of this method was significantly lower than that of plate culture method.The RT-qPCR method based on hsp70 mRNA was rapid,specific and highly sensitive,and used to assess the inactivation of pathogenic microorganisms in water.