SB-MBBR Technology: Treatment Strategies for Nitrification in Elevated Carbon Concentration Industrial Wastewater

Abstract

The dairy processing industry, in specific cheese processing, is a growing sector of the economy world wide. For example, China's demand for milk products projected an increase of 3.2-fold by 2050. While domestically in Canada, an annual increase of 5% has been reported since 2015 projected to continue to 2018. An increase in the demand for milk and dairy products translates to an increase in the produced wastewater. For every 2 L of milk processed 5 L of wastewater is produced, meanwhile, for every 1kg of cheese processed 9 kg of cheese whey is produced requiring the use of an estimated 10 kg of milk. Cheese whey is a by-product generated during the cheese manufacturing processes, with cheese processing wastewater defined as a combined stream of all wastewaters from a cheese processing facility.Cheese processing wastewater can be characterized as medium to high strength wastewater with COD concentrations of above 1000 mg·L -1 . In specific, cheese effluent can display COD concentrations in the range of 2500-5000 mg·L -1 and ammonia concentration in the ranges from 100-140 mg·L -1 -N, and total phosphorus is in the range of 50-60 mg·L -1 -P. Due to the high concentrations of carbon and nutrients in cheese processing wastewater, current stringent provincial regulations applied to municipal wastewater treatment plants restrict the discharge to sewers without prior treatment; leading to an increased demand for decentralized treatment units. Decentralized treatment units like sequencing batch reactors (SBR) gained popularity in cheesewastewater treatment due to their simple construct, reduced building expense and smaller footprint compared to conventional systems. The SBR however, has the potential of discharging floating or settled sludge during the draw or decant stages. The aerobic granular SBRs (AG-SBRs) promoted the formation of granules decreasing the potential of discharge. However, AG-SBRs were found to have problems regarding granular formation. The larger granules in an AG-SBR tended to ii of xii destabilize due to endogenous respiration within the granule resulting in its collapse and washout.While granule size affected nitrogen removal, smaller granules removed more nitrogen than larger granules. Replacing the granules with plastic carriers in an SBR introduced the sequencing batch moving bed biofilm reactor (SB-MBBR). The carriers eliminated the washout problem encountered in AG-SBRs as the biomass is retained on the carriers and remains in the reactor. It was postulated that an anaerobic, aerobic, anoxic (AOA) stage sequence would be ideal for dairy treatment using an SB-MBBR. AOA stage sequence allows for C, N, and P removal from a single reactor by selecting for the phosphorus accumulating organisms (PAOs), and nitrifiers. To date, however, the operation of an SB-MBBR with an AOA stage sequence treating wastewater from the food processing industry, in specific cheese wastewater has not been reported.Wastewater from a cheese making facility in eastern Ontario was modelled in a laboratory setting.The in...