پديد آورندگان :
قاسمي مقدم، امير دانشگاه تربيت مدرس , مختاراني، نادر دانشگاه تربيت مدرس - دانشكده مهندسي عمران و محيط زيست - گروه مهندسي محيط زيست , كاووسي، امير دانشگاه تربيت مدرس - دانشكده مهندسي عمران و محيط زيست - گروه مهندسي راه و ترابري
كليدواژه :
روسازي نفوذپذير , رواناب , COD , فسفر , جامدات كل
چكيده فارسي :
در اين تحقيق تاثير سنگدانه هاي مختلف در لايه هاي روسازي نفوذپذير جهت تصفيه رواناب شهري در مقياس آزمايشگاهي مورد بررسي قرار گرفته است. در اين راستا پس از تهيه سنگدانه هاي سرباره اي، سيليسي و سنگ آهكي و آماده سازي راكتور ها، آزمايش ها در سيكل هاي متوالي به صورت پيوسته با استفاده از رواناب سنتزي انجام پذيرفت. كليه آزمايش ها در راكتورهاي استوانه اي شكل به ارتفاع 60 سانتيمتر و قطر 20 سانتيمتر كه 50 سانتيمتر از ارتفاع آن (10 سانتيمتر لايه فيلتر و 40 سانتيمتر لايه اساس) توسط مصالح پر شده بود انجام شد. بر اساس نتايج بدست آمده اگر چه هر سه نوع سنگدانه مورد استفاده از توانايي قابل قبولي در تصفيه رواناب برخوردار بودند اما سرباره در مقايسه با ساير مصالح توانايي بالاتري در حذف آلاينده از خود نشان داد. در اين تحقيق حداكثر ميزان حذف COD، فسفر و جامدات از رواناب پس از گذشت 3 ساعت به ترتيب به ميزان 60، 59 و 70 درصد بوده كه پس از 120 ساعت به ترتيب به 98، 96 و 99 درصد افزايش يافت. همچنين در اين پژوهش ظرفيت جذب بار آلي، فسفر و جامدات در ستون هاي حاوي سنگدانه سرباره اي، به ترتيب برابر با 3/43، 0/21 و 22/10 گرم به ازاي هر كيلوگرم سنگدانه برآورد گرديد. در ادامه داده هاي تجربي فرايند حذف بار آلي با مدل هاي سينتيكي شبه درجه اول، شبه درجه دوم و مدل سينتيكي پخش بين ذره اي مطابقت داده شد. بر اساس نتايج حاصل، فرايند حذف بار آلي توسط هر سه سنگدانه مورد استفاده از مدل سينتيكي شبه مرتبه دوم تبعيت بيشتري داشته است.
چكيده لاتين :
Urban runoffs usually contain a large variety of pollutants such as heavy metals, organic compounds, nutrients, solids, and de-icing agents. These are normally accumulated on impervious urban surfaces over time. Hence, the runoff itself becomes a wastewater that could create substantial degradation of water quality in receiving area. There are many alternative management strategies for treating these contaminants. Most of the approved stormwater management measures are difficult to be implemented on a wide scale (due to infrastructure and space/cost constraints). Permeable pavement is one of the urban runoff management methods that are widely used in order to reduce storm runoff flow and volume, and minimize pollution conveyance to receiving waters. Pervious pavement systems consist of a permeable pavement surface layer and one or more underlying aggregate layers designed to temporarily store storm-water. Runoff treatment using three aggregate layers, namely steel slag, limestone and silica aggregates were applied both as filter and pavement base layers. The research was conducted at laboratory scale and in continuous mode. All the experiments were conducted in cylindrical reactors of 0.6 m height and 0.2 m diameter. Each column was filled up to an average depth of 0.5m (0.1 m for filter layer and 0.4 m for the base layer). In order to determine the lifespan of the media, synthetic runoff in successive cycles was injected into the column continuously. Results from the study showed that the base and the filter layers of the permeable pavement can reduce the total range of runoff pollutants effectively with high removal percentages. In all experiments the rate of pollutant removal at the initial time of reaction was faster. However, these were gradually decreased and after 120 hours approximately the maximum removal efficiency was achieved. Comparing the effects of the three aggregates types, the steel slag aggregates exhibited better performance. The treatment process showed that the maximum removal of COD, phosphate and total solids from runoff in 3 hours, were 61, 59 and 70 percent respectively. These were increased to 98, 96 and 99 percent after 120 hours. In addition, the total capacity of slag aggregates for removing COD, P-PO4 and TS parameters were estimated to be 3.43, 0.21 and 22.10 g/Kg respectively. The testing results indicated that after the slag aggregates, limestone materials showed a high ability to remove pollutants from runoff waters as compared with the silica aggregates. The kinetic study resulted that the pseudo-second order kinetics equation, compared with the pseudo-first order and intra-particle diffusion models, described better the removal of organic compound absorption (COD removal) from the storm water. In this study the rate constant of the reaction (K) for the COD removal via steel slag, limestone and silica aggregates were estimated to be 0.31, 0.31 and 0.30 g mg−1 min−1 respectively. The correlation coefficients (R2) under different conditions were also calculated to exceed 97%. Since steel slag is a byproduct of steel production factories, its application as a road-building material, would be an appropriate alternative pavement layer in protecting the environment and conserving the natural resources.
