Membrane and Desalination Technologies - TCE Moodle Website

Treatment of Food Industry Foods and Wastes by Membrane Filtration 265
ED utilizes an electrical driving force to transport ions through ion-exchange membranes.
The recovery of acid by ED is illustrated in Fig. 6.22. Table 6.5 lists common applications of
ED (8):
1. Demineralization of milk and whey
2. Desalting in a sugar refining plant
3. Downstream processing in a corn refining plant
4. Production of a high-quality biochemical product in a biotechnology plant
5. Downstream processing in a biotechnology plant
The bipolar process (Fig. 6.3) is a unique application of ED which can be used to generate
equimolar quantities of acid and base from salt. The principle of producing hydrochloric acid
and sodium hydroxide from sodium chloride by using the bipolar membrane is illustrated in
Fig. 6.3. The economics of using the bipolar process for the generation of acid and base in a
food processing plant is to be explored.
6. NONFOOD APPLICATIONS OF MEMBRANE TECHNOLOGY
IN THE FOOD INDUSTRY
6.1. Nutrient Removal from Wastewater Streams
Considering the increasingly stringent industrial effluent standards currently being
imposed on industrial effluent pretreatment facilities, specifically allowable concentrations
of nutrient-containing substances, the ability of RO to remove nutrients should be properly
investigated.
CA is still considered the preeminent membrane for wastewater treatment because it is
capable of producing the highest flux per unit surface area at specified levels of solute
rejection. The rejection performance of RO using a 90% sodium chloride rejection CA
membrane has been investigated (23). Phosphorous removal was greater than 95% in all
cases (greater than 99% in most cases). Ammonia removals were generally in excess of 90%,
and nitrite and nitrate removals generally ranged from 84 to 97%.
In an independent study of nutrient removal by RO conducted by the National Research
Council of Canada, Ottawa, Ontario, similar findings were confirmed: 80–90% separation of
sodium nitrate, sodium nitrite, and ammonium chloride were realized, with ammonium
chloride rejection significantly better than both sodium nitrate and sodium nitrite (39).
Rejection of phosphate-containing substances was also in agreement with separation efficiency
at greater than 98.5%.
Many food processing plants, including a major dairy plant in Minnesota, USA, use
phosphoric acid in their processes, resulting in over 100 mg/L of phosphate in their wastewater
streams. RO may be an ideal process for recovery and reuse of nutrients as fertilizers.
6.2. Organics Removal from Wastewater Streams
The rejection of inorganics (such as sodium chloride) generally is well defined. The
rejection of organics, which might be found in food industry wastewater, however, remains