Slaughterhouse waste is a serious environmental pollutant due to its high organic loadings including blood and proteins. It is similar to domestic wastewater with ahigher organic loading. These wastes are generally contain organic materials as well as suspended solids, resulting in a wastewater with high biochemical oxygen demand (BOD 5 ) and chemical oxygen demand (COD). The effective method for the slaughterhouse wastewater treatment is mainly biological methods. However, due tohighpollution ofslaughterhousewastes, traditional biologicalmethods are not typically efficient. Therefore, a combination ofmembrane andbiologicalmethodshas been appliedin thisstudy. Usingmembraneprocessesinwastewater treatmenthas been attracted great attention inrecent years. One of the newest and most effective methods is membranebioreactortechnology(MBR). MBRtechnology hasmany benefits such as highquality oftheoutputof theprocess, low space requirements,reduction ofinvestment costs and operatingsystem and quick setup. The purposeof this studyis purification of slaughterhouse waste bymembranebioreactor. At this process, hallow fiber membrane module with pore size of200nmimmersedin thebioreactor was used. An aerobic activated sludge was used in the biological process. Microorganisms were adapted to the slaughterhouse waste in the bioreactor for a three weeks period. After adaptation of themicroorganisms,the desiredphysical and chemicalproperties of the waste, including COD,5-day biochemical oxygen demand(BOD 5 ),turbidity, suspendedsolids, and theleakage of themembraneduring theprocess, were evaluated. Concentrationofmixedliquidsuspended solids(MLSS)in the MBR is locatedbetween4700 and9900mg/l. Thehydraulic retention timewas about25 hours. The critical flux of the membrane was obtained as 5.4 L/m 2 .h by flux-Step method which is based on operation of membrane at constant flux at 4.5 L/m 2 .h in the bioreactor. When the waste with organic loadingrate of4.9kgCOD/l (on average) was entered thebioreactor, concentrations ofCOD and BOD 5 inthe bioreactor outputduring the33-day operation weredecreased to171and59mg/l, respectively. The highestCODandBOD 5 removal efficiencyon the wholeprocess were obtained as 96%, whereas the turbidityof the input feed wasdecreased from 1112-836 NTUtoless than5.33 NTU. Keywords :Membranebioreactor, hydraulic retention time, turbidity, cloggingmembranes, hollowfibermembrane
