Meat Processing Plant Reuses Wastewater Using Continuously Cleaning Filtration

A meat processing plant in the U.S. incurred a high surcharge from a municipal waste treatment plant because its total suspended solids (TSS) levels were many thousands  of milligrams per liter (mg/L) above the allowable threshold. The factory installed an industrial waste treatment plant for water reuse and discharge using continuously cleaning filtration. (see Figure 1).

However, after water passed through the dissolved air flotation (DAF) device, the level of solids was still ~2,000 mg/l above the 20-micron particle size, which required high maintenance of the downstream bag filter. An automated filter technology was sought that could filter the large, 50-micron meat particles.

After a continuously cleaning filter was inserted between the dissolved air flotation and the bag filter, the TSS was reduced significantly—nearly 98 percent of the particles above 20 microns were removed (see Figures 2 and 3). As a result, the number of bag filter changes decreased by more than 80 percent—from ever 10 minutes to about every 60 minutes. It also improved performance of the proprietary downstream filter over an eight-hour period. For example, the filtrate flow of the proprietary downstream filter would decrease by 70 to 80 percent, but with the continously cleaning filter, it only decreased by 20 to 30 percent of its initial flow.

Ultimately, multiple particle filtration technologies were needed to treat the industrial feed water effectively. The dissolved air flotation removed fats, oils, and greases. Then the continuous cleaning filter removed the high level of fibrous meat particles. The bag filter was used as a safety filter before the ceramic filter, which removed submicron-size particles before the reverse osmosis membrane was used. The filtrate from the reverse osmosis membranes was used for general-purpose cleaning or discharged to the municipal waste treatment plant without incurring additional TSS surcharges.

Particle Size	Feed water TSS (mg/l)	Filtrate TSS (mg/l)	% Reduction
>50 um	1,885	40	97.8
38 – 50 um	24	0	100
32 – 38 um	16	0	100
20 – 32 um	7	0	100
Total >20   um	1,932	40	97.9

Figure 3: Total suspended solids (TSS) were reduced after a continuously cleaning filter was inserted between the dissolved air flotation and the bag filter. Feed water was measured after the dissolved air flotation step and filtrate was measured prior to the bag filter step. Figure courtesy of Dow Water & Process Solutions, Edina, Minn.