Recovery of brines from cheese making using membrane distillation at lab and pilot scale

Abstract

Brines are a problematic waste stream due to their high salinity. In cheese manufacturing, a salinity up to 220 g/l is used for the pickling bath. This waste stream is currently transported and treated externally at high costs. Membrane distillation is able to treat much higher salinities compared to the traditional desalination techniques. In this article, membrane distillation was therefore proposed as an alternative treatment technology, simultaneously allowing the recovery of the salts and the production of pure water. Microfiltration was successfully used as a pretreatment for the brines of two different companies. The denaturation temperature of the proteins was found at 65.5 °C and it was shown that the temperatures in the MD process should be below this temperature. Different membranes were explored at lab scale and module performance tests confirm the feasibility of MD at pilot scale for this application. Additionally, it was shown that the total water production costs are mainly affected by the availability of waste heat. Without waste heat, the lowest cost of 35 €/m3 is achieved for the 24 m2 modules, with a total thermal power demand of 34 kW. The costs for discharge of the brines are estimated at 50–150 €/m3, while the value of the salts recuperated equals 20 €/m3 distillate produced. Therefore, even when there is a low availability of waste heat, application of membrane distillation for the recovery of brines from cheese making is an economically viable and technically feasible alternative for external treatment.