eHT is currently providing planning, design, permitting, environmental clearance, and project management services for this project, valued at $57 million. eHT is the prime firm for this important wastewater treatment project and is supported by Parkhill. The lagoon WWTP serving the Town of Pecos (Town) was originally constructed in the 1980s. The Town’s WWTP has a current capacity of 1.6 MGD, though due to historical oil development in the area, the WWTP will need to be expanded to 3.5 MGD. However, the Town’s existing Texas Land Application Program (TLAP) permit utilizes the limit of the Town’s available land application site, and addition of a new Texas Pollutant Discharge Elimination System (TPDES) to support the additional flows will require significant nutrient removal capability, as the nearby receiving stream (Pecos River) has virtually no assimilative capacity for dilution of nutrients.

Further, the Town’s water supplies are currently limited to maximizing use of one of its wellfields (while minimizing use of the Town’s two other wellfields) due to water quality limitations. The Town anticipates in the future that additional water supplies will be needed and will likely need to come from implementation of some form of potable reuse strategy. For this reason, eHT evaluated various potable reuse alternatives and prepared recommendations for several treatment regime approaches for a direct potable reuse (DPR) program once the Town is ready to proceed toward producing a new raw water source.

To support future treatment needs for both wastewater treatment and a future DPR project, the Town’s WWTP must be capable of meeting requirements for Type I reuse in this project as well as providing the appropriate “building blocks” for a future DPR program. Implementation of an automated SCADA system, enhanced energy efficiency and biological and chemical nutrient removal capability are all key components for successfully meeting these treatment objectives. eHT based the project on processes including Biological Nutrient Removal (BNR) and Membrane Bioreactor (MBR) technologies in order to prepare for future DPR polishing processes, such as Reverse Osmosis (RO), UV Advanced Oxidation Processes (UV-AOP), Ozone and/or Biologically Active Contactors (BAC) technologies in the future.

The treatment systems ultimately selected were based on required construction footprint, repurposing of existing structures as a budget control measure, capital and operational cost, operational flexibility, lead time for construction and capability of meeting treatment goals for cBOD, TSS, ammonia, and total phosphorus. The Town’s upgraded WWTP will include both coarse and fine mechanical screens, a grit removal system, an influent wastewater pump station, flow equalization systems, a secondary BNR process designed for enhanced biological phosphorus removal, enhanced energy recovery and tertiary filtration using MBR membrane filters, chlorine disinfection and aerobic solids digestion and disposal.