مقايسه پرتوهاي گاما و اشعه ماوراي بنفش در كنترل رشد مجدد ميكروارگانيسم ها در پساب فاضلاب شهري

Comparison of gamma ray and ultraviolet radiation on regrowth control of microorganism in urban sewage effluent

زﻣﯿﻨﻪ و ﻫﺪف: اﺳﺘﻔﺎده از ﭘﺴﺎب ﻓﺎﺿﻼب ﺑﻪ ﻣﻨﻈﻮر ﮐﺸﺎورزي ﺑﻪ دﻟﯿﻞ ﮐﻤﺒﻮد ﺷﺪﯾﺪ ﻣﻨﺎﺑﻊ آب در اﯾﺮان، اﺟﺘﻨﺎب ﻧﺎﭘﺬﯾﺮ ﺷﺪه اﺳﺖ. ﮔﻨﺪزداﯾﯽ ﯾﮑﯽ از ﻣﺮاﺣﻞ ﻣﻬﻢ در ﺗﺼﻔﯿﻪ آب اﺳﺖ. ﻫﺮ ﭼﻨﺪ ﻓﻦ آوري ﻫﺎي ﮔﻨﺪزداﯾﯽ راﯾﺞ ﻣﺎﻧﻨﺪ ﮐﻠﺮزﻧﯽ ﻣﯽ ﺗﻮاﻧﻨﺪ ﺑﻪ ﻃﻮر ﻣﻮﺛﺮي ﻋﻮاﻣﻞ ﺑﯿﻤﺎرﯾﺰاي ﻣﯿﮑﺮوﺑﯽ را ﮐﻨﺘﺮل ﮐﻨﻨﺪ، ﻟﯿﮑﻦ ﻣﺤﺼﻮﻻت ﻧﺎﺧﻮاﺳﺘﻪ ﮔﻨﺪزداﯾﯽ را اﯾﺠﺎد ﻣﯽ ﮐﻨﻨﺪ ﮐﻪ ﺳﻤﯽ و ﺳﺮﻃﺎن زا ﻫﺴﺘﻨﺪ. ﻫﺪف ﻣﻄﺎﻟﻌﻪ ﺣﺎﺿﺮ ﻣﻘﺎﯾﺴﻪ ﮐﺎراﯾﯽ ﮔﻨﺪزداﯾﯽ و ﮐﻨﺘﺮل رﺷﺪ ﻣﺠﺪد آﻟﻮدﮔﯽ زﯾﺴﺘﯽ ﭘﺴﺎب ﻓﺎﺿﻼب ﺷﻬﺮي ﺑﺎ اﺳﺘﻔﺎده از ﺗﯿﻤﺎر ﻫﺎي ﭘﺮﺗﻮ ﮔﺎﻣﺎ و اﺷﻌﻪ ﻣﺎوراءﺑﻨﻔﺶ ﻣﯽ ﺑﺎﺷﺪ. روش ﺑﺮرﺳﯽ: ﻧﻤﻮﻧﻪ ﭘﺴﺎب ﺛﺎﻧﻮﯾﻪ )ﻗﺒﻞ از واﺣﺪ ﮐﻠﺮزﻧﯽ( از ﺗﺼﻔﯿﻪ ﺧﺎﻧﻪ ﺗﻬﺮان ﺟﻨﻮب ﺟﻤﻊ آوري ﺷﺪ. از دزﻫﺎي ﭘﺮﺗﻮ ﮔﺎﻣﺎ 4 ،2 ،1 ،0/5 و 6 ﮐﯿﻠﻮﮔﺮي اﺳﺘﻔﺎده ﺷﺪ. ﺳﯿﺴﺘﻢ ﮔﻨﺪزداﯾﯽ اﺷﻌﻪ ﻣﺎوراي ﺑﻨﻔﺶ ﺑﺎ ﺣﺠﻢ راﮐﺘﻮر 1 ﻟﯿﺘﺮ ﺳﺎﺧﺘﻪ ﺷﺪ. ﮐﺎراﯾﯽ ﮔﻨﺪزداﯾﯽ ﺑﺮ اﺳﺎس ﺗﻌﯿﯿﻦ ﺷﻤﺎرش ﮐﻞ ﮐﻠﻨﯽ و ﮐﻠﯿﻔﺮم ﮐﻞ ارزﯾﺎﺑﯽ ﺷﺪ. ﺟﻬﺖ ارزﯾﺎﺑﯽ رﺷﺪ ﻣﺠﺪد ﻣﯿﮑﺮوﺑﯽ ﻧﻤﻮﻧﻪ ﻫﺎ در دﻣﺎي 22درﺟﻪ ﺳﺎﻧﺘﯽ ﮔﺮاد و 100 دور در دﻗﯿﻘﻪ در ﻣﺤﻞ ﺗﺎرﯾﮏ ﺑﻪ ﻣﺪت ﺳﻪ روز اﻧﮑﻮﺑﻪ ﺷﺪﻧﺪ. ﯾﺎﻓﺘﻪ ﻫﺎ: ﺗﻌﺪاد ﮐﻠﯿﻔﺮم ﮐﻞ در ﺷﺮوع آزﻣﺎﯾﺶ در ﻫﻤﻪ دزﻫﺎي ﭘﺮﺗﻮ ﮔﺎﻣﺎ ﺻﻔﺮ ﺑﻮد. ﻟﯿﮑﻦ در دزﻫﺎي ﮐﻤﺘﺮ از 2 ﮐﯿﻠﻮﮔﺮي رﺷﺪ ﻣﺠﺪد ﮐﻠﯿﻔﺮم ﮐﻞ ﻣﺸﺎﻫﺪه ﺷﺪ. در ﺗﯿﻤﺎر اﺷﻌﻪ ﻣﺎوراي ﺑﻨﻔﺶ ﺷﺪت ﺟﺮﯾﺎن ورودي، در زﻣﺎن ﺷﺮوع آزﻣﺎﯾﺶ در ﺷﺪت ﺟﺮﯾﺎن ﮐﻢ ﺑﯿﺸﺘﺮﯾﻦ ﮐﺎراﯾﯽ ﮔﻨﺪزداﯾﯽ وﺟﻮد داﺷﺖ. ﻟﯿﮑﻦ ﺑﺎ ﮔﺬﺷﺖ ﺳﻪ روز در ﻫﻤﻪ ﺷﺪت ﺟﺮﯾﺎنﻫﺎ ﺟﻤﻌﯿﺖ ﮐﻠﯿﻔﺮم ﮐﻞ از ﺣﺪ ﻣﺠﺎز ﺑﯿﺸﺘﺮ ﺑﻮد. ﺑﺤﺚ و ﻧﺘﯿﺠﻪ ﮔﯿﺮي: ﭘﺮﺗﻮﺗﺎﺑﯽ ﮔﺎﻣﺎ ﻣﯽ ﺗﻮاﻧﺪ ﺑﻪ ﻋﻨﻮان ﯾﮏ ﺗﮑﻨﯿﮏ ﻣﻮﺛﺮ ﻧﺴﺒﺖ ﺑﻪ روش ﻣﺎوراي ﺑﻨﻔﺶ ﺟﻬﺖ ﮔﻨﺪزداﯾﯽ ﺑﺪون رﺷﺪ ﻣﺠﺪد ﻣﯿﮑﺮوﺑﯽ ﺑﻪ ﮐﺎر رود.

Background and Objective: Due to the severe shortage of water resources in Iran, the application of wastewater effluent for agriculture has become inevitable. Disinfection is one of the crucial steps in water treatment. Common disinfection technologies such as chlorination can effectively control microbial pathogens; however, undesirable disinfection byproducts (DBPs) are known to be toxic and carcinogenic. Therefore, the present study aimed to compare disinfection efficiency and regrowth control of microorganisms in urban wastewater effluent using gamma radiation and Ultra Violet treatments. Method: The pre-disinfection effluent (before chlorination unit) was collected from south Tehran wastewater treatment plant, Tehran, Iran. The applied gamma radiation doses were 0.5, 1, 2, 4 and 6 kGy. UV disinfection systems were developed using a reactor with 1 L of liquid volume. The disinfection efficiency was evaluated based on the total colony count and total Coliform. For bacterial regrowth evaluation, the samples were incubated at 22 ◦C, 10orpm for three days in dark condition. Findings: The number of total Coliform in all gamma ray doses was zero at the beginning of the experiment. The re-growth of total Coliform was observed at doses less than 2 kGy. In the treatment of ultraviolet radiation, at the beginning of the experiment, the lowest flow rate had the highest disinfection efficiency. However, after three days, the total Coliform population was higher than the allowed limit in all of the inflow rates. Discussion and Conclusion: Gamma radiation can be applied as an effective alternative technique to UV treatment for disinfection processes without bacterial regrowth.