Characteristics of canteen wastewater and other commercial food service facilities differ significantly from residential wastewater. Due to its high amount of organic matter, oil and grease and suspended solids, it causes higher biochemical oxygen demand (BOD). Oil and grease present in a form of low-biodegradable and frequently cause problems for both on site sewage disposal systems and public sewer systems. The water in contact with the free oil and grease (FOG) had high levels of oil approximately 800 mg/L and this may indicate the poor FOG management practices (Williams et al. 2012). Oil and grease in wastewater can exist in several forms: free, dispersed or emulsified. The differences are based primarily on size. In an oil-water mixture, free oil is characterized with droplet sizes greater than 150 μm in size while dispersed oil has a size range of 20–150 μm and emulsified oil has droplets typically less than 20 μm (Hu 2002). The majority of oil in canteen wastewater is free oil which can be removed by an overflow weir grease trap (Pollution Prevention Regional Information Center 2014). A grease trap is a chamber designed for wastewater pass through and allow any free or mechanically emulsified oil to float to the surface. Then clear wastewater can be treated in the next wastewater treatment unit. Although grease trap tanks are supposed to prevent oil and grease to enter the sanitary sewer line, high grease loads, emulsified grease, and surge wastewater loadings often cause oil and grease bypass the grease trap tanks. Some researchers found that grease trap tanks showed the removal efficiency between 43 and 80 % (Wong et al. 2007; Wongthanate et al. 2014).
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- Preliminary Study of Rapid Enhanced Effective Micro-organisms (REEM) in Oil and Grease Trap from Canteen Wastewater
- Chapter 6
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