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Water treatment and recovery in the dairy industry

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Year 2013 

Project location Factory of Grupo Kalise Menorquina in Palau de Plegamans, Cataluña.

Objectives Water treatment to reach local discharge limits. Optimization of investment costs and operation and maintenance costs. Optimization of oxygen injection system with special blowers AquaJET. Reuse of 300 m3/day of wastewater. Adaptation capacity to possible future expanding of the plant.

Installed equipment

  • Aeration biological reactor with oxygen ejection system AquaJET. 
  • Ultrafiltration membrane tank MBR, including cleaning system. 
  • Reverse Osmosis system, including cleaning system. 
  • Instrumentation, control and operation panel.

Capacity 300 m3/day.

Background

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

The Sigma water treatment system is designed to increase overall efficiency through: i) the separation of the aeration and filtration processes by membranes and ii) the use of highly resistant and durable submerged membranes with patented techniques to optimize their cleaning.

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 filtering in order to obtain the liquid-solid separation, followed by a third reverse osmosis process for a final finish and obtaining water of sufficient quality to be reused in the industrial process.

Process description

SIGMA MBR plants are designed to optimize membrane performance by specifically designing the hydraulic systems and flows through the membranes. The wastewater is introduced into the aerobic zone where it is mixed with the sludge flow coming from the membrane zone. Biomass concentrations of 10000 mg/L are reached in the biological reactor, with a SRT of 15 days. The aeration system using AquaJETS recirculation nozzles allows a high oxygen transfer with yields of 45%, no need for maintenance inside the tank and complete independence of aeration-agitation needs in the same equipment. After the biological treatment, the high solid content liquor is pumped to the submerged membrane area where it is filtered. The submerged membranes are made of hollow fiber and work according to the outside-in principle, designed with Puron advanced technology by Koch, 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 washing with a current of water in the opposite direction with the permeate itself and air as the driving force. Occasionally, membrane modules are immersed in a chemical cleaning solution. 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 conditioning and final control of conductivity, elimination of salts and organic matter to obtain reuse water. 

ParameterUnitsValue of inlet/outlet Removal efficiency
Reactor Sigma MBR 
TSS

mg/L 

200 / 10 

95% 

COD

mg/L 

8000 / 200 

97.5% 

BOD5

mg/L 

5000 / 100 

98% 

Reverse Osmosis

Conductivity

μS/cm 

4000 / 370 

90.8% 


Process diagram 

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