Recovery of spent CIP Solutions

Presented By N.E.M Business Solutions
Tel / fax 01823 680119   mobile  07768 981196

The discharge of effluent to the sewer or for on-site treatment has become increasingly expensive. Most industries have already reduced their water consumption to a minimum. However, efficient cleaning often produces a large volume of caustic effluent, even with CIP systems that re-use the detergent a number of times. 

However  it is now possible to recover more than 90% of a spent caustic solution by using pH resistant nano filtration membranes. This gives reduced operating costs and better performance that the traditional centrifugal separator method.

Membrane filtration was introduced to the food industry more than 30 years ago. Sterile filtration, protein concentration, desalination and dewatering are typical membrane processes which individually or in combination find their uses in the manufacture of liquid foods. 

A membrane is often characterised by its pore size and Molecular Weight Cut Off (MWCO). Membrane materials are generally either ceramic or polymeric materials. Ceramic membranes are only available in the ultra filtration / micro filtration range, whereas polymeric membrane MWCOs cover the entire filtration range.

Until recently, only the ceramic membranes could withstand the extreme pH of a caustic or acid CIP solution. However, as ceramic membranes were only available in the more open ultra filtration / micro filtration range, the attempts to use them for the recovery of spent CIP solutions only resulted in limited success; too much COD  (Chemical Oxygen Demand    a measure of a substances polluting capacity)  simply passed through the relatively large pores of the  ceramic membranes.

Temperature and pH resistant tubular polymeric nano filtration membranes for CIP solution recovery are now on the market. Several years of experience with commercial installations have proved their ability to cope with extreme process conditions.

A tubular shape is often chosen as this minimises the need for pre-filtration (although in practice this is still a worthwhile exercise). The MWCO of the nano filtration membrane allows the NaOH and water molecules to pass freely, but retains more than 90% of the COD contributing components (soiling and debris from the plant being cleaned)

This means that a plant equipped with these membranes separates the spent CIP solution into two streams: the purified non-foaming caustic representing 90% of the feed volume containing less than 10% of the initial COD, and a concentrate of just 10% of the feed volume containing more than 90% of the initial COD.

A CIP Chemical Recovery System equipped with the above mentioned membranes can process the CIP solution at temperatures up to 70C and is ideal for the recovery of tank, pipeline and bottle washer CIP solutions. Consideration must be given to the molecular size of some detergent additives, as very large molecules may be filtered out with the debris. Discussions with your detergent supplier should expose any potential problems.

For systems which use the CIP solution a number of times before discharge a small CIP Chemical Recovery System continuously treating a part of solution (Kidney mode) will keep the COD level at a constant acceptable low level.

For CIP systems where the solution is used only once before it is discharged there is no hope. This type of system is both financially and environmentally stupid. A simple recovery tank and a few control valves will vastly reduce the running cost of any "single shot " system, chemical recovery is then the "icing on the cake".

Like most other industries the food and beverage industry faces an increased focus on effluents discharged to the sewage system, and the higher the COD, the higher the discharge costs. Purchase of cleaning chemicals and water represents a significant cost which it is desirable to minimise without compromising on cleaning effectiveness. 

A chemical recovery system offers a useful tool to increase both the environmental and economical effectiveness of any CIP system.

2002

N.E.M Business Solutions        Tel / Fax  : 01823 680119     Mobile   07768 981196 

E-mail   neil@nem.org.uk