BA in Liberal Arts and Engineering Studies
Liberal Arts and Engineering Studies Program
Michael Haungs, Jane Lehr
In 2014, Firestone Walker began the implementation of an onsite Wastewater Treatment Plant to treat the brewery’s process wastewater. Although the secondary treatment of aerated lagoons was capable of lowering the effluent to Paso Robles discharge requirements, Firestone Walker considered investing in a tertiary treatment to reclaim water for industrial reuse in wash down, evaporative coolers, and steam generation.
The information required to determine to optimal tertiary treatment system included the effluent levels leaving the lagoons, the influent requirements for the reclamation uses, the discharge requirements from Paso Robles, and the flow rate of the process wastewater. With this information, different filtration and disinfection systems were measured to determine the optimal treatment system to compliment the Nanofiltration system.
Overall, the recommended tertiary treatment is a Slow Sand Filtration system, followed by a Nanofiltration system, and ending with an Ultraviolet system. The combination of these three treatments should produce an effluent that matches the requirements set in the California Code of Regulations Title 22 for recycled water quality levels.
Slow Sand Filtration was chosen for its comparatively inexpensive capital cost, ease of maintenance, and avoidance of chemicals or backwashing. Nanofiltration was chosen for its specialization in lowering total hardness and its ability to use a lower feed pressure than Reverse Osmosis, resulting in lower energy requirements and higher permeate levels. Ultraviolet was chosen for its ability to disinfect most known pathogens without the creation of dangerous by-products or use of chemicals.
Each of the system capital costs are estimates that lay on the conservative side, and each will fluctuate depending on the actual flow rate of the system and quality of the effluent entering the system. However, the current estimated total capital cost is $353,250 with an estimated annual operations and maintenance cost of $32,440. Although the average Nanofiltration system can recover 85%-95% of the feed water, using a slightly lower recover rate of 80% results in a Return on Investment of 15.55 months. Again, as this number is highly uncertain and depends on actual capital cost and percentage of water reclaimed, an ROI Matrix was created to allow quick identification of possible ROI values once these values are known. So long as the expected annual growth rate remains at 25%, the information in the matrix will remain valid.