By David Pearson
Evaporators are used extensively in the dairy industry as a method of removing water from a fluid to obtain a more stable or reduced volume product. Often, the resulting concentrate is subsequently dried to a powder.
The water condensed during evaporation is hot and may contain a small amount of the product itself. This "carry over" in the vapor is due to splashing or boiling of the product during the evaporation process, which creates a mist of tiny particles that can be distilled over into the condensate along with the water. For this reason, the evaporator condensate – although relatively pure – can contain enough organic material to support bacterial growth when cool. This makes the condensate unacceptable for re-use in any food-related environment.
One dairy processor, however, recently began filtering evaporative condensate through a reverse osmosis (RO) membrane (see Figure 1), thus discovering a valuable source of hot, good-quality rinse water. Based on energy, freshwater, effluent disposal and other cost savings, this system effectively paid for itself in just six months (see Figure 2).
Compared with conventional water treatment systems, an RO plant requires relatively little space (about 30x10 feet for the system referenced here) and often can be custom designed to fit into the existing available space on site, so normally there's not a need for plant expansion to accommodate the condensate recycling system. Other advantages can be summarized as follows:
