The addition or removal of British thermal units from process chemical products is one of the greatest cost centers for the petro-chemical industry. When transferring heat across metal, as is the case in heat exchangers, many factors influence the efficiency of the transfer. This is of primary concern to any large scale operation, as it can translate to millions of dollars in savings or losses per year in fuel consumption costs.
The Bison Wastewater Treatment Plant in Beaumont, Texas, needed a way to treat its waste stream generated from hydro-blasting heat exchangers out of refineries and other heavy industry in a continuously recycled loop.
Blue Sphere Water Technology took to the task of designing the system, which would start with a specially designed floor sump. The sump was oversized to achieve a low water velocity to aid in settling of dense solids, and it also uses three chambers, which allows one chamber to be cleaned while it remains in service.
A 60,000-gal, above-grade holding tank outfitted with a blower and air lance system stores dirty water until it is pumped to the three-chamber chemical reaction tank, where coagulant, caustic soda and an emulsion polymer are added for the desired chemical reaction. Primary solids are removed through dissolved air flotation (DAF), and effluent from the DAF gravity-drops into a clear well tank, at which point operators can judge the water quality through visual inspection.
Two stainless-steel, seven-position #2 bag filter housings treat water from the clear well to capture residual suspended solids. Then the water enters a 60,000-gal clean-water holding tank to be used as process water. A supply header outfitted with a pressure transducer is tied to the inlet of the hydro-blasters. When the transducer detects a drop in pressure on the header, the pump ramps up to meet the demand.
Additionally, Blue Sphere fabricated custom stainless steel base plates for transfer pumps—for both solids-laden water and treated water—so that corrosion would not be an issue.
Construction began after the buildings were finished in October 2016 and Blue Sphere Water Technologies finished the wastewater plant in mid-December of the same year. While the plant was constructed, it was not until 2017 that operations began at the plant. Heavy rainfall in Beaumont delayed some aspects of the work and created challenges for contractors due to muddy conditions. The general contractor used wooden mats to stabilize the site roads during the worst of the events to keep the project on schedule, and ultimately, it came in under budget.
Since starting operations, the plant has processed more than 5 million gal of wastewater without significant equipment failure or shutdown. As the water is reused in the process, the mineral content increases. The sources of mineral introduction include the material from the exchangers, namely chloride and sodium from the chemical products and evaporation processes, to a smaller degree. When the conductivity of the loop exceeds the threshold of 2,000 µS/cm, the loop is blown down, meaning a constant stream of treated water is removed from the loop with vacuum trucks.
The removed water is taken to a centralized waste treatment facility to be discharged in compliance with a pretreatment permit. Blue Sphere continues to monitor the data from the facility to determine if additional technology could improve operations, particularly a reverse osmosis unit that could consolidate mineral content in a smaller volume of water to minimize disposal costs.