تصفیه خاک آلوده به شیرابه توسط فرایند ازن زنی

اندکی پس از تولید مواد زائد، تولید شیرابه آغاز شده که از منابع آلاینده خاک و آب‌های زیر‌‌زمینی به شمار می‌رود. امروزه فرآیند ازن زنی به‌عنوان یک روش پرکاربرد در تصفیه خاک‌های آلوده مورد‌استفاده قرار می‌گیرد. ازن در تصفیه گستره وسیعی از آلاینده‌ها کاربرد دارد. از آنجایی‌که شیرابه در برگیرنده مجموعه‌ای از آلاینده‌های آلی و معدنی است، بنابراین فرایند ازن زنی می‌تواند نقش مفیدی در ‌تصفیه خاک‌های آلوده به شیرابه داشته باشد. در این مطالعه کاربرد فرایند ازن زنی جهت پالایش خاک آلوده به شیرابه حاصل از فرایند کمپوست زباله شهری در مقیاس آزمایشگاهی موردبررسی قرارگرفته است. در این تحقیق اثر پارامترهای زمان واکنش، دبی ازن زنی، ph محیط، پیش‌تصفیه ازن، میزان مواد آلی خاک و همچنین حضور اکسیدهای فلزی بر راندمان حذف مواد آلی از خاک موردبررسی قرارگرفته است. بر اساس نتایج آزمایش‌ها حداکثر راندمان حذف به میزان 11.2% پس از 120 دقیقه ازن زنی با دبی200 میلی‌لیتر بر دقیقه و در ph حدود 9 حاصل شد. همچنین با افزایش آلودگی اولیه خاک راندمان حذف مواد آلی افزایش یافت. در این پژوهش حضور اکسید آهن 3 ظرفیتی باعث افزایش 42 درصدی در راندمان حذف مواد آلی خاک گردید. براساس آزمایشات صورت پذیرفته، ازن پس از عبور از مجاورت اسید توانسته است در ph حدود 9، پس از گذشت 120 دقیقه، مواد آلی خاک مورد مطالعه را به میزان 21.2 درصد کاهش دهد که در مقایسه با راندمان حذف با استفاده از گاز ازن بدون پیش‌تصفیه نزدیک به90% افزایش، نشان می‌دهد.

Leachate Contaminated Soils Treatment with Ozonation Process

By developing of the consumerism and rapidly progress of industrial and commercial lifestyle in most of the countries, the solid waste production has been growth rapidly in the recent years. The leachate production starts shortly after the production of waste and cause the pollution of environment and especially contamination of the soil. Chemical processes are usually considered as the most effective processes for degradation of soil pollutants. In these processes, the chemical reagents are added to make the desired reactions take place. But it is sometimes necessary to increase the amount of reagents so that the reactions take place completely. This may cause chemical reagents to remain in the soil. Ozone, which acts as a powerful oxidizer, is capable of degrading organic pollutants in a short period of time without producing any toxic residuals. Nowadays ozonation has become one of the most favorable processes in soil remediation technologies. Ozone is used in the treatment of a wide range of pollutants. Due to the high diffusion coefficient of ozone, all of the present pollutants in soil are theoretically available for this oxidant. Since leachate contains a range of organic and inorganic pollutants, ozonation process is therefore can be a useful process in treating soils contaminated with leachate. In this study, application of ozonation process as an exsitu method on the treatment of composting leachate polluted soil was studied in laboratory scale and in batch mode. Experiments were conducted using a cylindrical Plexiglas reactor with the diameter of 3 cm and the height of 60 cm. Ozone gas was continuously passed through a diffuser at the bottom of the reactor. Ozone generator with 5 g/h nominal capacity was used to produce ozone gas from pure and dry oxygen. Ozone content was measured with a digital ozone analyzer. A rotameter was also applied to measure the volume of gas injected to the reactor. The leachate used in this study has been collected from one of composting plant in north of Iran. The soil used in this study was mainly silica with the particle size of 0.120.3 mm. In order to pollute the soil; a certain amount of leachate was well mixed with the soil and then dried to the desired humidity. According to the results the maximum removal of soil organic content was obtained at pH=9 after 120 minutes ozonation with a flow of 200 ml/min. By increasing the initial organic content of the soil, the removal via ozonation has been also increased. In other word the soil with higher initial contaminations has shown better removal efficiencies compared with the one with lower initial pollutants. In this study, the presence of trivalent iron oxide caused 42% increases in soil organic content removal efficiency. In this research applying gas washing technique with acid also greatly enhanced the removal efficiency of ozonation process. According to the conducted experiments, after pre washing of ozone with acid, the removal of soil organic content with nearly 90% increase, reached to 21.2%. The results were also shown that, the change in the type of acid did not have a significant effect on the soil organic matter removal efficiency.