mergerin neutralizingtanks beforebeing discharged in the waste-waternet.
Here a considerable quantity of dissolved, biologically non-degradable,
inorganic salt concentrationsoccur,whichpassthroughthe sewagetreatment
plantsand subsequentlychargethe outfallditch.The ideais to reducethe salt
load in the wastewaterby using agentsfor scaling-off the soiling,whichcontain
less chemicals thanthe usualcleaning agents.
An example for this approach comesfromthe detergent industryfor textile
cleaning. The detergent industryhas beensuccessful at reducing chemicals by
usingdifferent enzymes(see below), and at loweringthe requiredtemperatures
in the washingliquor(energysavings). Alsofor the dish-washingformulae for
industrial kitchens, cateringserviceand restaurants, hospitals,etc. enzymes are
being successfully used (e.g. in the product neodisher bioClean’ of the
Chemischen Fabrik Dr. Weigert, D-20539 Hamburg, Germany,
http://www.drweigert.de)..)
A field where the use of enzyme-based cleaning agentshas beenlargely
established is the reprocessing of membranesfor micro-, nano-and ultra-
filtration as wellas for reverse osmosis of variousproducts of the foodindustry.
Membrane processes are, for example,usedin the beverage industryfor clearing
and clarifying juices,wineand beer,in the starchindustry for starch cleaning, in
slaughter housesfor waste-water cleaning(Allieet al., 2003),in egg product
manufacture for concentratingalbuminsand egg, and in dairies for fractionating
whey proteins (Arguello et al., 2003), or for concentrating cheese whey
(Kessler, 1996).In the course of the filtration process the membraneporesare
plugged up with particles fromthe filtration substrate (preferably withhigher
molecular protein substances), so thatthe permeate flux dropsdownto an
acceptable bottomlimit at a givenmaximumtrans-membrane pressure. To
restore the filtrationperformance, the pores of the membraneshaveto be
completely cleaned.Herecleaning agentsare usedthat dissolve the substrate
molecules accumulated in the membrane pores,or decompose theminto smaller
components to be subsequently removed.For the hydrolysis of higher molecular
proteins, alkaliswitha pH higherthan12 are usuallyusedfor temperatures
beyond 60 ÎC. These conditions representno problem for the ceramicor
zirconium oxidemembranesapplied in microfiltration, but maydo for the
polysulphonicmembranes, particularlythe celluloseacetatemembranesusedfor
ultrafiltrationand reverseosmosis. For material-sparingreprocessingof these
pH sensitive (andexpensive) membranes,enzymatic cleaningagents(e.g.the
EcolabproductsP3-ultrasil53, 54, 60b, 62 and 65 ) havebeendevelopedand
applied.
Afterthe successful use of enzyme-containing recipesin the aforementioned
fieldsof application,comprehensive assays for the use of enzyme-basedrecipes
in furtherfieldsof application wereprimarilyperformedin the dairysector.
However, despite the positive resultsobtained, these assays cannot yet be
considered as complete.
Enzymatic cleaning in foodprocessing 517