Wastewater pretreatment system uses sequenced reactors to cut costs & save energy at Houston facility
The system uses a sequence of closed vertical reactors to get the benefits of trickling filters and attached growth.
In 2013, the Dr Pepper Snapple Group (DPSG) bottling facility in Houston commissioned the Baswood BioViper biological pretreatment system as its wastewater treatment platform. After more than five years of continuous operation, the Baswood system has successfully treated more than 8 million lb of biochemical oxygen demand (BOD) and exceeded expectations in both energy reduction and cost savings.
Sustainability & Stewardship
Beverage manufacturer DPSG has long been an advocate of environmental sustainability. With the high organic content of effluent from bottling operations, energy and water usage at these facilities have a significant impact on the environment, as well as cost implications. DPSG sought a solution to help sustainably reduce these effects.
As part of its corporate-wide sustainability initiative, DPSG established clear goals for reducing manufacturing water use and wastewater discharge per gallon of finished product. At the DPSG bottling facility in Houston, the company saw an opportunity to enhance its stewardship of the local community, while supporting sustainability goals.
In 2012, the company selected the Baswood Corp. BioViper fixed media biological pretreatment system to provide a wastewater solution that complemented other operating efficiency and sustainability initiatives already in place at the Houston plant. By reducing BOD levels in the water discharged from the plant and consuming less energy with the system, DPSG could treat its effluent more efficiently and reduce the environmental impact of its operation. The installation of the system was completed in February 2013.
The treatment system at DPSG Houston sequences proven technologies in closed, vertical reactors, maximizing the traditional benefits of both a trickling filter and attached growth without the challenges that often accompany these methods. The system consists of three BioViper reactors in a series. Raw wastewater from the bottling plant temporarily is stored in the flow equalization tank. The wastewater pH is adjusted when necessary before being pumped into the first reactor.
Each reactor is an enclosed-tank reactor which utilizes fixed, plastic media to encourage organic biomass growth in the form of biofilms. Wastewater and the internal recirculation stream are blended along the pipeline and evenly distributed onto the top of the media via nozzles mounted on top of the tank cover. The water travels through two zones of fixed media, namely the trickling zone and the submerged zone. The media in the trickling zone are exposed to the surrounding air. The media in the submerged zone are immersed in the bulk mixed liquor. A fiber grate is used to support the plastic media in the reactor, as well as provide clearance from the coarse-bubble diffusers installed on the tank floor.
As the diffusers deliver air from the blowers into the mixed liquor, some of the oxygen is utilized by the biomass on the submerged zone media. The residual oxygen in the submerged zone is off-gassed and then used by the biomass in the trickling zone. Organic pollutants (BOD) in the wastewater are degraded during oxygen consumption.
Internal recirculation via a pump that transfers the mixed liquor from the submerged zone to the distribution nozzles ensures sufficient wetting of the media in the trickling zone and substrate distribution onto the tank’s cross-section area. Air supply to the reactor passes through a positive displacement blower.
The forward wastewater is transferred from one reactor to the next via a transfer pump. The low sludge production of the system means the effluent from the last reactor (less than 400 mg/L total suspended solids) can be discharged directly to the publicly owned treatment works (POTW) without further solid-liquid separation.
These systems offer low cost of ownership, due to the minimal labor and energy requirements. Because the reactor is a permanent fixed media system, there is no cleaning or replacement of media needed. Moreover, while aerators are used to supply air to meet the respiratory needs of the biomass, the configuration of the system eliminates the need for blowers to maintain solids or media in suspension. As a result, maintenance requirements and energy needs are reduced.
The biomass is periodically pruned through the dry cycle anaerobic/aerobic digestion (DCAD) process. At regular intervals, one of the three vessels is rotated out of treatment. This process effectively prunes the biomass, and endogenous respiration prevents plugging up the system. Through DCAD, robust and rejuvenated biomass remains captive in the system.
The entire process is SCADA-controlled and managed automatically through the remote monitoring capability. The system has no internal moving parts, only requires chemicals to balance pH and uses readily available off-the-shelf components—further reducing operational and maintenance costs.
Long-Term Efficiency & Savings
The system at DPSG Houston currently manages an average daily flow of 165,000 gal and treats approximately 5,800 lb of BOD per operating day. The system was initially expected to deliver at least 75% BOD reduction; however, as the biomass has become acclimated, the actual BOD-reduction rate has increased to 90% or higher.
Over a five-year period, the site has processed an estimated 8.2 million lb of BOD and more than 240 million gal of water. The city of Houston adds surcharges when BOD effluent is above 300 mg/L, and the reactor system has consistently stayed below that threshold. Local municipality surcharges have varied over the years, but have averaged approximately $0.76 per lb of BOD, so the cost savings to DPSG have been significant.
When comparing kWh/lb of BOD removed, the system requires 26% the power of a standard municipal treatment system, reducing the plant’s environmental impact. The system also uses 79% less power than with membrane bioreactors and 29% less power compared to moving bed biofilm reactors. This has saved roughly 6,325 metric tons of carbon dioxide from being produced at the DPSG plant—the carbon footprint equivalent of keeping 1,341 cars off the road for a year.
“Baswood’s innovative solution at the Houston bottling facility has exceeded our expectations and significantly reduced the impact of our business on natural and municipal resources, while improving our operating efficiency,” said Derry Hobson, executive vice president, supply chain for DPSG.
The BioViper system is modular and scalable, with a small physical footprint. Capacity can be increased by adding reactors to an existing system. The system at DPSG Houston is running at nearly its design capacity. Treatment capacity upgrades with an additional reactor are under consideration at this time.
Due to the success of the installation in Houston, DPSG installed a second system at its beverage manufacturing facility in Ottumwa, Iowa, in 2016.
“We are proud that the BioViper system has exceeded all expectations at DPSG Houston,” said Paul Kamholz, vice president for Baswood. “The data proves that our solution consistently delivers a much higher quality treatment of water, and that has helped DPSG achieve a meaningful reduction in energy use and operating costs.”