Ag Processing Inc. (AGP) is a farmer-owned cooperative that processes, markets, and transports grains and grain products. Since its formation in 1983, AGP has grown to include 175 local cooperatives representing over 250,000 farmers throughout the Midwest.

Challenge

AGP doubled its biodiesel production capability with the acquisition of the former East Fork Biodiesel LLC plant near Algona, Iowa. This plant has a rated capacity of 60 million gallons (227 million liters) of biodiesel production annually. It needed a reliable wastewater treatment system to keep up with production demands.

Solution

ADI Systems completed the installation of an ADI®​ membrane bioreactor system (MBR) and later assisted with start-up and commissioning of the system to treat wastewater generated at the Algona plant. The MBR system treats all wastewater discharged from the biodiesel plant and produces a high-quality final effluent.

The MBR system consists of one 15,000 gallon (57 m3) influent equalization tank, which stores wastewater pumped from a skimmer tank. Supplemental nitrogen and phosphorus chemicals are dosed into the equalization tank in order to satisfy the growth requirements for biomass in the MBR system. Two submersible pumps in the equalization tank deliver wastewater to a 96,500 gallon (365 m3) preaeration tank, where the bulk of the organic removal takes place.

Waste activated sludge produced in the MBR system is delivered to a dewatering press, which thickens the waste solids and returns pressate back to the MBR system for treatment.

Mixed liquor from the preaeration tank is pumped to the two 1,700 gallon (6 m3) modular membrane tanks housing membrane units. This process achieves the final liquids/solids separation and ensures complete biomass retention within the MBR system.

Results

The MBR provides AGP with a compact, easy-to-operate wastewater treatment system. The MBR system was designed to treat this high-strength wastewater with a flow rate up to 8,500 gpd (32 m3/d) and design biochemical oxygen demand (BOD) and total suspended solids (TSS) concentrations of 17,500 mg/l and 2,130 mg/l, respectively.

The MBR consistently meets its design effluent objectives of < 10 mg/l BOD, < 10 mg/l TSS, and < 1 mg/l ammonia-nitrogen (NH3-N), allowing AGP to remain in compliance with strict environmental regulations.