Food Processing Plant Design Proposal for Economical Waste Water System
This Food Processing Plant packages various meat products. The waste water is currently being run through grease traps, but is then discharge into the Michatoya River without further processing. Current effluent is 2050 COD and 1600 BOD, TSS is 674 mg/L and the Plant needs to meet progressively lower effluent targets:
Current Targets: Immediate 2015 May 2016 2024
1600 BOD 1280 768 460
674 TSS 400
The available land that can be used to build a waste water system is very limited, and standard WWS designs would therefore be very expensive. Quotes have exceeded $500,000…and would have cost overruns, high operating costs and would require a DAFT System to further separate out Fats, Oils and Grease in order to work properly.
Therefore, BluePlanet reviewed the long-term regulations and requirements, and based on the fact that the primary goal is to lower COD and TSS is not currently considered a major problem. As such, we can recommend a straight forward aeration system with multiple chambers, effectively creating a 3-Stage System. Each successive Stage would operate at a lower Food to Mass ratio, as the waste water passes from Stage 1 to 2 to 3. This creates a slightly different environment for degrading the waste, which results in good reductions in COD / BOD, as well as TSS…but will still rely on the current grease traps to remove the more difficult to degrade FOGs.
The system proposed would utilize an aeration tank some 75 to 80 Meters in length X 6 Meters wide X 4.5 Meters deep. This will require that the tank be dug into the ground 2 to 2.5 Meters…and built some 2 to 2.5 Meters above ground. Dirt from the dig can be used as a buttress to help structurally support the side walls. That being said, a local cement contractor should review and sign-off on a structural design, but we assume that 3000 LB, 10 Inch, continuous poured feral (Rebar) cement should be adequate to construct the tank. The interior of the tank should have two dividing walls included, forming three equal chambers. In these dividing walls, a pass-through window should be installed, allowing the waste water to flow from one chamber to the next equal to the flow rate per hour…which is 900m3 per day. Windows should have their bottoms at say 4 Meters, assuring maximum retention times. A simple tin-roof system should be constructed over these tanks, lower rain water dilution. In addition, each chamber will be equipped with an aeration system, which must have diffusion and horse power confirmed, but this is a matter for our Bio-Engineer to evaluate and confirm, as noted below.
Based on this flow, we will have at least a 2-Day retention time in the three chambers which, based on the recommended dosage schedule of ACF-32, the system should lower the 1600 BOD by 70 to 80 percent…and should have a discharge of between 320 and 480. Increased dosage will be able to help in the future, and monitoring results will be done to optimize the performance.
ACF-32 Gallons Stage 1 Stage 2 Stage 3
First Week-applied each day 1 gal ½ gal ½ gal
Thereafter…end of day
Sun/Tues/Thurs/Fri 3/4 gal ½ gal ½ gal
Optimizing based on performance could raise or lower dosage by 25 percent over time, but would anticipate first year dosage at some 370 to 380 gallons of ACF-32.
We recommend an Aeration System using a Blower versus a Compressor, providing a Lower Pressure (PSI at 18) at a Higher Volume (CFPM 2800), defused by engineered design nozzle lay-out. Desser Roots’ RAM Blowers could deliver this at approximately 100 kw. We suggest setting up each stage with its own system, and purchase one extra as a serve. While we are in the process of confirming the requirements for PSI and CFM…for operating comparisons, 300 kw 24/7 would be a good target.
(Actual Specs: 140-3550 ICFM, 18 PSI, 3-170 bhp, 2.2-127 kw for basic RAM Blower)