Cleaning-in-place in the dairy industry: criteria for reuse of caustic (NaOH) solutions

Abstract

-Cleaning-in-place NaOH solutions from a milk standardisation dairy plant are reused for several days before being discharged to the purification station. During reuse the surface tension of the industrial cleaning solutions was reduced from~70 mJ . m -2 for newly prepared NaOH down tõ 30 mJ . m -2 during the week. The decrease was rapid during the first few reuse cycles and stabilised thereafter, while the polluting load and suspended solids increased inversely. The cleaning efficiency test consisted of an ultrafiltration membrane fouled with whey proteins, which was cleaned using these cleaning solutions, either without any treatment, or following crossflow micro-and nanofiltration. It was found that microfiltrates and nanofiltrates with both low surface tension and suspended solids resulted in higher efficiency and cleanliness, and a much faster cleaning rate. The effects of suspended solids and low surface tension will have to be further studied to determine the role of each parameter and confirmed on stainless steel surfaces and in a milk processing plant. . La diminution est rapide pendant les premières dizaines de cycles puis se stabilise ensuite, tandis que la charge polluante et les matières en suspension augmentent. L'efficacité et la vitesse de nettoyage par ces solutions industrielles, sans traitement ou après épuration par microfiltration ou nanofiltration tangentielle, ont été quantifiées à l'aide d'une méthode utilisant une membrane d'ultrafiltration colmatée par des protéines de lactosé-rum. Les microfiltrats et les nanofiltrats sont plus efficaces que la solution industrielle réutilisée dont ils proviennent et même que la solution de soude caustique fraîche. 357

The role of surface tension of re-used caustic soda on the cleaning efficiency in dairy plants

“…Recent work Merin, Ge´san-Guiziou, Boyaval, & Daufin, 2002) has shown that re-use of caustic solutions induces a progressive increase in concentration of suspended solids (SS) and of chemical oxygen demand, both total (COD t ) and soluble (COD s ). This causes a decrease in surface tension (g) of the cleaning solutions, to levels around 30 mJ m À2 in the course of the cleaning cycles.…”

Environmental Impact of Wastewater Discharges from FERMENCAM

“…The pH is acidic, values measured in the different points (Table 2) are different from those found in Table 1; these variations are linked to an overdose of acid-base cleaning products [10]. This magnitude of the pH shift is detrimental to the environment [11].…”

Membrane Separation Process in Wastewater Treatment of Food Industry

“…There are a number of works describing how to recover contaminated cleaning solutions by membranes (Choe et al, 2005;Fernández et al, 2010;Gésan-Guiziou et al, 2002Merin et al, 2002;Räsänen et al, 2002). Dresch et al (2001) pointed out the NF technology as a promising technique compared to decantation, centrifugation and microfiltration (0.1µm cut-off) for the regeneration of waste NaOH solutions from an industrial CIP system.…”