بررسي تاثير شوك ناشي از كاهش دما بر روي نرخ نيتريفيكاسيون

ABRUPT COLD TEMPERATURE SHOCK EFFECT ON NITRIFICATION Rate

در اين تحقيق، پس از انجام نيتريفيكاسيون مختصر در يك راكتور جريان جانبي ناپيوستهي متوالي تحت شرايط مناسب از جمله دماي 30 درجهي سلسيوس و با هدف توليد بيومس مناسب، براي بررسي انجام نيتريفيكاسيون در راكتوري ديگر، بيومس اضافي براي تنظيم سن لجن به راكتور ناپيوسته تحت شرايط مختلف بهره برداري وارد و نرخ ويژهي نيتريفيكاسيون مورد بررسي قرار گرفت. نتايج حاصل پس از تجزيه و تحليل آماري نشان داد كه با استفاده از روش تاگوچي مي توان تاثير ساير عوامل به جز عامل موردنظر (مثلاً دما) را بر نرخ واكنش حذف كرد. بر اين مبنا مشخص شد كه شوك كاهش دمايي باعث كاهش قابل ملاحظهي نرخ واكنش تا 25، 55 و 78 درصد به ترتيب براي كاهش دما از 30 به 25، 20 و 15 درجهي سلسيوس ميشود و بر اين اساس ضريب تصحيح دمايي براي اكسايندگان آمونيوم معادل 0965/1 بهدست آمد.

Biological processes are known as temperature-sensitive in wastewater treatment. Nitrification and, especially, partial nitrification (first step of nitrification) are the most temperature-sensitive among biological processes. Factors such as dissolved oxygen, ammonia concentration, MLVSS, and etc, may influence two steps of the nitrification and organism growth rate, so nitrification should be done by controlling some of these factors. In this study, biomass acclimation in a side stream partial nitrification sequencing batch reactor (SBR) under optimum conditions (e.g. T=30?C) for biological nitrogen removal (BNR) has been examined. In order to show the superiority of ammonia oxidizing biomass (AOB) over nitrite oxidizing biomass (NOB), excess sludge for solid retention time (SRT) regulation was added to another batch reactor, which had been performed under different conditions (e.g. T=25, 20 and 15?C) for specific ammonium oxidation rate (sAOR) evaluation and cold shock effect consideration. Results of the side stream, partial nitrification, sequencing batch reactor showed that the specific ammonium oxidation rate at the end of any cycle and after steady state conditions was about 16.4 mgN–NH4+ gr VSS / hr. Primary results of main stream batch tests after analysis by the Taguchi method displayed that the percent influence of consideration factors includes temperature, initial ammonium, MLVSS and time, whose specific ammonium oxidation rates were about 98.5, 0.09, 0.06 and 1.3%, respectively. So, temperature is an important factor that affects the specific ammonium oxidation rate. More analysis on the results has shown that the effects of other factors, except the considered factor (e.g. temperature), on specific ammonium oxidation rate can be eliminated using the Taguchi method. Based on this method, it was demonstrated that abrupt cold shock caused a significant reduction in the process rate; up to 25, 55 and 78% for temperature reduction, from 30 to 25, 20 and 15?C, respectively. Therefore, the temperature correction factor was calculated about 1.0965 by elimination of other factors except temperature. The temperature correction factor was also estimated to be about 1.106 using direct comparison.