English abstract
Demands on dairy products is expected to be increased in the future, though dairy industry consumes huge amount of freshwater, and produces effluents which can cause some serious problem to the environment. Therefore, dairy industry wastewaters (DIW) must receive adequate pretreatment to meet the governmental discharge standards before they discharge into the main sewerage pipelines, to conserve the environment as well as to avoid wastewater shock loads. In this study, five wastewater samples from SQU dairy plant were taken for five different days and pretreated using pH adjustment method combined with Dual-Media Filter System (DMFS) method to investigate the removal efficiency of organic pollutants. The DMFS contains three different layers of granular activated carbon (GAC), coarse sand and fine sand from the top to the bottom respectively. Moreover, batch adsorption experiment has been conducted using various dosages of Moringa Peregrina (MP) for the initially treated wastewaters to determine the optimum adsorbent dose for Biological Oxygen Demand (BOD5), Chemical Oxygen Demand (COD) and turbidity removal. Raw dairy wastewater pH was adjusted to around 5, before these pretreated wastewaters were passed into DMFS with 12 cm GAC layer, and parameters; BOD5, COD, pH, EC and turbidity were measured before and after each pretreatment method. The study results show that the overall BOD5, COD and turbidity removal efficiencies of this integrated pretreatment method are 69%, 91% and 99% respectively. In addition, 100 mg L-1 of the MP treatment showed 37% removal efficiency of COD concentrations; meanwhile, 300 mg L-1 dosage of the MP reduced about 21% of BOD5 levels. Moreover, turbidity was observed to decrease with increasing adsorbent dosages. On the other hand, results indicate that the mean BOD5/COD ratio of the pretreated dairy wastewater was 0.64. The final average BOD5 and COD concentrations were 1,019 mg L-1 and 2,091 mg L-1 respectively, which are relatively close to the Omani standards for discharge of non-household liquid waste into sewage system. However, it has been suggested that biological treatment can be combined with this integrated physiochemical treatment to obtain further BOD5 and COD loadings reduction.
