@article { author = {pirsaheb, meghdad and moradi, masoud and Sharafi, Kiomars}, title = {Evaluation of Activated Sludge with a Submerged Fixed Bed in the Removal of Phosphorus and Nitrogen Compounds from Hospital Wastewater}, journal = {Journal of Water and Wastewater; Ab va Fazilab ( in persian )}, volume = {26}, number = {3}, pages = {28-36}, year = {2015}, publisher = {Water and Wastewater Consulting Engineers}, issn = {1024-5936}, eissn = {2383-0905}, doi = {}, abstract = {Aerobic treatment processes with fixed growths exhibit a high efficiency not only in the removal of organic materials and phosphorus but also in the nitrification process (conversion of ammonium to nitrate) in wastewater. The present study aims to evaluate the performance of activated sludge with a submerged fixed bed in the removal of phosphorus and nitrogen compounds from wastewater. For this purpose, a reactor was initially constructed and commissioned before the activated sludge with a submerged fixed bed was loaded. A total number of 225 samples were collected from the wastewater treatment plant at Farabi General Hospital in Kermanshah to evaluate the removal efficiency of ammonia nitrogen, total nitrogen, nitrite, nitrate, and phosphate over three different retention times (2.9 hours of aerobic and 1.1 hours of anaerobic operation; 3.6 hours ofaerobic and 1.4 hours of anaerobic operation; and 4 hours of aerobic and 1.5 hours of anaerobic operation). Phosphorus, ammonia nitrogen, nitrite, and nitrate measurements were performed according to the Standard methods 4500-P, 4500-NH3, 4500-NO2, and 4500-NO3, respectively. Results showed that the highest phosphorus removal (53%) was achieved with Phase III of the system (i.e., 4 hours of aerobic plus 1.5 hours of anaerobic operation) while the highest ammonia nitrogen removal (97%) and TKN (96%) were achieved in Phase II of the system (i.e., 3.6 hours of aerobic and 1.4 hours of anaerobic operation). Significant differences (Pvalue<0.05) were observed among the mean values for the removal efficiencies of these parameters in the three retention times. The optimum time for the removal of ammonia nitrogen was estimated at 3.6 hours of aerobic and 1.4 hours of anaerobic operation and that for the removal of phosphorus was 4 hours of aerobic and 1.5 hours of anaerobic operation. Based on the results obtained, it may be claimed that the activated sludge process with the submerged fixed bed exhibits a high efficiency for the removal of phosphorus and nitrogen compounds from hospital wastewater only if the system is properly operated and maintained.}, keywords = {hospital wastewater,Biofilm,Fixed Growth with The Submerged Bed,Phosphorus,Nitrogen Compounds}, title_fa = {بررسی کارایی لجن فعال با بستر ثابت مستغرق در حذف فسفر و ترکیبات نیتروژنه از فاضلاب بیمارستانی}, abstract_fa = {فرایندهای تصفیه هوازی با رشد چسبیده ثابت، کارایی بالایی در حذف مواد آلی و فسفر و نیز انجام نیتریفیکاسیون در فاضلاب دارند. هدف از این مطالعه بررسی کارایی لجن فعال با بستر ثابت مستغرق، در حذف فسفر و ترکیبات نیتروژنه از فاضلاب بیمارستانی بود.ابتدا اقدام به ساخت راکتور، راه‌اندازی و بارگذاری سیستم لجن فعال با بستر ثابت مستغرق شد و سپس برای بررسی راندمان سیستم در حذف ازت آمونیاکی، ازت کل، نیتریت، نیترات و فسفر در سه زمان ماند مختلف یعنی 9/2ساعت هوازی و 1/1 ساعت بی‌هوازی،  6/3 ساعت هوازی و 4/1 ساعت بی‌هوازی، 4 ساعت هوازی و 5/1 ساعت بی‌هوازی، اقدام به برداشت 225 نمونه از تصفیه‌خانه فاضلاب بیمارستان فارابی کرمانشاه شد. اندازه‌گیری فسفر، نیتروژن آمونیاکی، نیتریت و نیترات به‌ترتیب طبق روش استاندارد شماره 4500-P، 4500-NH3، 4500-NO2 و 4500-NO3 انجام گرفت. بالاترین میزان درصد حذف فسفر یعنی 53 درصد، در مرحله سوم سیستم (4 ساعت هوازی و 5/1 ساعت بی‌هوازی) و بالاترین حذف ازت آمونیاکی یعنی 97 درصد و TKN 96 درصد در مرحله دوم سیستم ( 6/3 هوازی و 4/1 بی‌هوازی) بود. مقایسه میانگین راندمان حذف این پارامترها در سه زمان ماند مورد بررسی، اختلاف معنی‌داری را نشان داد (05/۰