Multi-Stage Study of Wastewater from Bakery Enterprises for the Ability to Clean Using Chemical Coagulation Processes and Combined Methods of Biological Treatment

Commercial bakeries producing cakes, pies, cookies, biscuits, brownies, rolls, and a variety of other desserts generate wastewater with high loads of suspended solids, fats, oils, and grease (FOG) and high chemical oxygen demand (COD) and nutrients like ammonium nitrogen and nitrate-nitrogen which are too high for discharge to a municipal sewage system without pre-treatment. Due to the complex nature of this wastewater, it requires a multi-step solution. The objective of the present investigation is to perform a multiple-step treatability study of bakery wastewater such as chemical treatment using chemical coagulant, secondary treatment in anaerobic sequencing batch reactors (ASBR) with anaerobic bacteria, and finally aerobic treatment in a batch-fed reactor by the development of acclimatized seeds for both carbon oxidation and nitrification with subsequent study of the flow of chemical and microbiological processes in dynamics. A composite wastewater sample was collected from a nearby bakery plant located in Dhulagarh, West Bengal. After necessary characterization observed COD value was within a range of 4500 mg/L whereas ammonium nitrogen (NH4+-N) and nitrate nitrogen (NO3--N) level was found in the range of 57 and 69 mg/L as N respectively. Simulated synthetic bakery wastewater was prepared in the laboratory. Chemical treatment was done using alum and polyelectrolyte to reduce mostly the organic materials present in the wastewater in the form of COD as the values of COD, NH4+-N, and NO3--N were found within a range of 3000, 48, and 82 mg/L as N respectively after chemical treatment. For reduction of the residual high value of COD and nitrate nitrogen content of chemically treated real-life bakery wastewater anaerobic sequencing batch reactors (ASBR) were provided. Finally aerobic treatment was done for the final clarification of the wastewater. After three stage treatment process effluent wastewater become free from both organics and nutrients.