بهينه سازي تصفيه شيرابه كمپوست با استفاده از فرايند اكسيداسيون پيشرفته H2O2/UV

Optimization of Compost Leachate Treatment Using Advanced Oxidation Process H2O2/UV

كمپوست به عنوان يكي از اين روش هاي بازيافت زباله ها به كود مي باشد. يكي از مشكلات موجود در اين فرايند، مديريت شيرابه است كه اثرات نامطلوبي بر محيط زيست و سلامتي دارد. شيرابه به دليل داشتن تركيبات آلي پيچيده كه به روش زيستي به سختي تجزيه مي شوند، به تصفيه شيميايي از جمله اكسيداسيون پيشرفته نياز خواهند داشت. در اين مطالعه كارايي فرايند H2O2/UV براي تصفيه شيرابه كمپوست تصفيه شده توسط روش بيولوژيكي در سيستم ناپيوسته مورد بررسي قرار گرفت. هدف از اين مطالعه ارزيابي بازده فرايند آب اكسيژنه با تابش UV(H2O2/UV) به منظور حذف اكسيژن خواهي شيميايي (COD) و رنگ و كدورت با استفاده از روش پاسخ سطحي (RSM) در طرح مركب مركزي (CCD) بود. شرايط عملياتي مختلف شامل pH اوليه، دز آب اكسيژنه و زمان تماس با UV به منظور كاهش آلاينده هاي شيرابه كمپوست براي بهينه سازي حداكثر حذف آلاينده ها بررسي شد. تعداد 20 تيمار انجام شد. شرايط بهينه درpH اوليه 5/7، دز آب اكسيژنه mL/L 3/2 و زمان تماس با UV در 95 دقيقه حاصل گرديد. ميزان حذف COD، رنگ و كدورت شيرابه توسط فرايند H2O2/UV در شرايط بهينه حذف با روش پاسخ سطحي به ترتيب %32/12، %83/20 و NTU 68/8 به دست آمد. نتايج نشان داد فرايند H2O2/UV در كاهش كدورت موفق تر بوده است و در حذف COD كارايي چنداني نداشته است.

Continuous population growth and enhancement of human life have led to an increase in waste production. Thus, waste management has become a problem of many countries. Over recent years, organic wastes management policies have been increasingly tending toward recycling. Compost process is widely applied to transform wastes into fertilizers, in which leachate management is a problem due to its adverse effects on the environment and human health. Control, collection, disposal, and treatment of leachate requires a special attention to prevent soil, surface and ground water contamination. The leachate contains toxic organic compounds and phenolic compounds. The first are resistant to biodegradation, nitrogen, aromatic and the latter threats human and aquatic life. This is why the leachate requires chemical treatment including advanced oxidation processes (AOPs). Combining UV radiation by the hydrogen peroxide (H2O2) is one of the advanced oxidation processes. During photolysis, UV radiation directly breaks down a complicated compound to more simple ones, by more energy than the compound binding energy. High energy cnsumption enhances the costs of this method. So it can be improved economically by controling parameters including pH and UV contact time that affect oxidation process. The leachate effluent was prepared from composting plant, Golestan, Iran. The leachate was characterized immediately after transferring to the lab. Furthermore, samplings were carried out three times to measure COD, BOD, total suspended solids (TSS), and turbidity of the stored samples. Total nitrogen contents of unviable cells were analyzed by Kjeldahl determination (2300 Kjettec Analyzer Unit, Foss Tecator, Sweden). The RSM approach used in the present study was under a CCD approach including four independent variables; initial pH, H2O2 and UV contact time. The design consisted of 2k factorial points augmented by 2k axial points and a center point where k is the number of variables. The two operating variables were considered at three levels; low (-1), central (0) and high (+1). With the RSM approach, ANOVA was carried out for a second-order response surface model. The significance of each coefficient was determined by the F-values and the values of probability (prob>F). The larger the magnitude of the F-value and the smaller the p-value, the more significant the corresponding coefficients. Values of ‘prob> F’, less than 0.0500, also indicate highly significant regression at a 95% confidence level. A total number of 20 experimental runs was set. Optimal condition obtained for H2O2/UV process were of initial pH 7.5, hydrogen peroxide of 2.3 mL/L, and UV-contact time of 95 min. In these conditions, the removal rates of COD and color and turbidity for H2O2/UV process were 12.32%, 20.83%, and 8.68 NTU, respectively. The RSM applied in this study can present the effects of the operating variables as well as their interactive effects on the responses. In the present study, most effective factors on the advanced oxidation process including pH, hydrogen peroxide dosage and UV-contact time were tested. The results indicated that the H2O2/UV process has been successful in reducing turbidity but not in COD removal efficiency.