GULF COAST WASTE DISPOSAL AUTHORITY (GCWDA) INTRODUCTION The Gulf Coast Waste Disposal Authority (GCWDA) Washburn Tunnel Facility, a large high-rate activated sludge plant in Pasadena, Texas, is capable of processing about 2.1 x 105 m3/day (55 MGD). The 9.7 ha (24 ac) site includes primary treatment facilities for barscreening and grit removal and primary clarification. Nutrient addition, pH control, and cooling towers are used to prepare the primary effluent for introduction to the complete-mix aeration basins which are equipped with mechanical surface aerators. Effluent from these basins is passed into one of two secondary clarifiers, where a percentage of the sludge is wasted to a filter press-incinerator installation, and the remainder is cycled back to the aeration basins. Sludge centrifuges, and a control building, control systems, and a minicomputer are also at the site. All clarification and aeration basins have concrete walls and bottoms. Two spill lagoons located at the east side of the plant are used only when extremely toxic or concentrated wastes are accidently introduced to the plant and must be diverted and reintroduced slowly to avoid system upset. The plant treats six industrial waste streams and discharges to the Houston Ship Channel. Presently, sludge is barged to an off-site landfill but it will eventually be burned in a new incinerator. HISTORY GCWDA participation in industrial waste treatment was authorized under the statute creating the authority, adopted by the Texas Legislature in September 1969. The letter of agreement GCWDA signed in September 1970 with five industries was the initial step in forming the first joint waste treatment facility in the Gulf Coast area. Compatibility-treatability tests, funded by the industrial participants, were used to determine if the individual wastes could be combined in a single biological treatment plant. In November 1970, the Texas Water Quality Board approved the concept of joint treatment contingent upon proof of waste compatibility and authorized GCWDA to proceed with the project. Contracts between GCWDA and the industries were signed in May 1973. Subsequently, $25 million in bonds were issued; $12-1/2 million were to go to the purchase of an existing 1.7 x 105 m3/day (45 MGD) treatment plant. The contract also stipulated that, following the bond sale and plant purchase, GCWDA would become owner and operator of the facility. Under the terms of the agreement, the participating industries contracted to pay all bond amortization, maintenance and operating costs, plus a management fee to the GCWDA in the amount of $120,000 annually. In 1973, an expansion program was begun which would provide an additional biological train and sludge handling facility and expand the plant capacity to 2.1 x 105m3/day (55 MGD). The total cost of the expansion, $14 million, was financed by the remainder of the original bond issue. LOCATION The Washburn Tunnel Facility is located in the city of Pasadena on the east side of Houston, Texas (Figure 26). The facility is on the southern shore of the Houston Ship Channel, and the plant effluent is discharged to the channel. The Vince Bayou is to the west of the facility and the Washburn Tunnel (an automobile tunnel under the ship channel) is located to the east (Figure 27). REGIONAL CHARACTERISTICS Refinery and petrochemical production and storage facilities are the major industries of the area. This southeastern portion of Texas contributes 30 percent of the total U.S. petrochemical output. The ship canals and nearby Galveston Bay and Gulf of Mexico provide excellent transportation routes for raw materials and finished products. Crude oil from nearby petroleum reserves in Texas, Oklahoma, and Louisiana is easily piped or trucked into the area. The land is relatively flat, and underground pipelines are easily installed and serviced. The advantages cited above have made industrial property adjacent to the ship canals a popular and relatively expensive commodity. Because land costs are prohibitively high, waste treatment designers have avoided sprawling, land-intensive lagoon treatment schemes. The Washburn Tunnel has a low surface-to-volume ratio typical of process schemes consisting of separate, deep basins. This has mandated the use of innovative techniques for waste temperature control prior to biological treatment. Temperatures in the Gulf Coast region of Texas are moderated by coastal winds, with summer daily maximums in the low thirties (degrees centigrade, Table 63). Rainfall is fairly evenly distributed throughout the year, and the annual rainfall exceeds average potential evapotranspiration. A large portion of the rainfall occurs within short periods of time and results in excessive runoff or local flooding. Relative humidity is highest along the coast and decreases inland. According to climatological data (113), the mean annual relative humidity at Central Standard Time, varies from approximately 60 percent near the coast to around 35 percent in the West Texas desert region. Recurring weather conditions_limit to 60 percent the possible total annual sunshine. Tropical cyclones occasionally pass through the Texas coastal zone; high winds and floodings, especially extreme tidal fluctuations near the coast, cause a great deal of damage. Effects of the storms in the vicinity of the Washburn Tunnel Facility are limited primarily to wind or tornado damage with occasional flooding. WASTE IDENTIFICATION Sources In 1976, four industries discharged aqueous waste streams to the Washburn Tunnel Facility. One additional industry discharged both aqueous and concentrated sludge waste streams. The treatment plant influents are summarized below: |