Recovering energy, nutrient and water from waste water of bulgur plants

In this study, recovering energy, nutrient and water from wastewater of bulgur plants were investigated. Especially, the washing and cooking steps are important operations in bulgur processing due to the significant amount of water usage and disposal. At present, the wastewater from the washing and cooking operations is discharged without any recovering operation in the industry. Washing (20 °C) and cooking (97 °C) were made using 1 and 2 ratios of water to 1 ratio of wheat, respectively. The wastewater obtained from the washing and cooking was treated with filtration, centrifugation and column which contains sand, activated carbon and resin, and then finally treated with UV. Before and after the treatments, the properties of water (DO, BOD5, color values, pH, turbidity, conductivity, total solid content, Brix and microorganism load only for the washing wastewater) were determined to find the effect of the treatments. It was found that these treatments were significantly (p<0.05) effective on the reduction of the BOD5 values from 311.5 to 169.9 and from 429.5 to 93.7 mg/l, for the washing and cooking, respectively. For both wastewater, the treatments improved the color values (L*, a*, b*, YI). Total solid content, Brix, conductivity and turbidity decreased. In addition to the recovering treatments, the wastewater of cooking was used in the next cooking operation by mixing with fresh water. It was found that the reuse of wastewater could be possible for the subsequent cooking operations. Also, the nutrients leached during the cooking lead to increase the BOD5 value of the wastewater of cooking. At this point, the spray drying method was used to recover the nutrients. The spray dried product can be used in ready soup, baby foods recipes, because of containing 19 % protein, 10 % starch and 12 % ash. According to the result, 73.4 and 49.5 % of wastewater can be obtained from the washing and cooking operations, respectively. Additionally, one bulgur plant, having 50 tons/day capacity, can save nearly $ 70524 and 19080 tons of water, annually. The net profit after the evaluation of investment cost, processing cost, salvage value and service life of system was calculated as $ 51524. Keywords: wastewater, recovery, bulgur, cooking, washing, energy, water, nutrient