Wastewater treatment and reuse in the dairy industry

Scenario

Grupo Kalise Menorquina is an ice cream and dairy dessert manufacturing company. The discharge from its facilities in Palau de Plegamans is characterized by high COD, good biodegradability and high concentration of fats and solids. 

The Sigma Water Treatment System is designed to increase overall efficiency by: i) separating the aeration and membrane filtration processes and ii) utilizing high strength and durability submerged membranes with patented cleaning optimization techniques. 

The first part of the plant consists of a double process of aeration of activated sludge with a high concentration of suspended solids, followed by a second process with submerged membranes for filtration to obtain the liquid-solid separation, followed by a third process of reverse osmosis for final finishing and obtaining water with sufficient quality to be reused in the industrial process.

Description of the process

SIGMA MBR plants are designed to optimize membrane performance by specifically designing the hydraulics and flows through the membranes. The wastewater is introduced into the aerobic zone where it is mixed with the sludge stream coming from the membrane zone, in the biological reactor biomass concentrations of 10,000 mg/L are reached, with a TRC of 15 days. The AquaJETS aeration system with recirculation nozzles allows a high oxygen transfer with 45% efficiency, no need for maintenance inside the tank and complete independence of the aeration - agitation needs in the same equipment. After biological treatment, liquors with high solids content are pumped to the submerged membrane zone where they are filtered. The submerged membranes are hollow fiber membranes operating on the outside - inside principle, designed with Koch's advanced Puron technology, with a total filtration surface of 1000 m². The membranes separate the liquid part from the solid part and the liquid (permeate) is sent to a storage tank, while the solids are recirculated to the biological reactor. The submerged membranes are periodically cleaned by backwashing with a reverse flow of water using the permeate itself and air as a motive force. Occasionally, the membrane modules are immersed in a chemical cleaning solution. The residual sludge is sent out of the plant for final disposal. This design ensures reduced operating costs and extended membrane life. Finally, the Reverse Osmosis membrane system allows the final conditioning and control of conductivity, elimination of salts and organic matter to obtain water for reuse. 

Process diagram