Case Study

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Challenge
High costs and declining reserves make water a valuable resource in Mexico. International Truck and Engine Corporation's 1,080,000-sq. ft. assembly plant in Escobedo, Nuevo Leon, Mexico, is located in the middle of Mexico's northern desert. The plant requires several thousand gallons per day (gpd) of water to produce more than 200 medium and heavy trucks daily. Using fresh water would place an inefficient cost burden on the plant while simultaneously straining the rapidly dwindling local drinking water supply. Moreover, local discharge limits prohibited International from disposing of concentrated waste streams such as RO rejects and acid and caustic streams in local waterways.

Solution
International selected a Siemens zero liquid discharge (ZLD) system to meet their water needs. The ZLD system combines a number of wastewater treatment technologies, including:

• Sanitary collection
  
• Biological water treatment
  
• Microfiltration membrane softening
  
• Reverse-osmosis (RO) water recycling and
  
• Evaporation ponds

A Memtek crossflow tubular membrane system is used for softening during pretreatment to ensure the water is acceptable for the manufacturing processes. Crossflow tubular membranes are also used in the wastewater treatment process prior to RO recycling. The RO units are operating at 90% recovery due to the high quality of feed water produced by the microfiltration system. Permeate is chlorinated and directed to a 100,000 gallon water storage tank to be split amongst different facility activities.

Result
The ZLD system has served International very well. More than 119,000 gallons of reusable water is produced daily. The system significantly lessens the demand on the fresh water supply and the number of discharges into local waterways.

SOURCE: Siemens Industry, Inc. - Water Technologies