The San Antonio River Authority (SARA) operates three wastewater treatment plants northeast of San Antonio, Texas, including the Salatrillo, Upper Martinez, and Martinez II facilities. The plants provide a combined treatment capacity of about 10 mgd, with 5.83 mgd treated at the Salatrillo
Wastewater Treatment Plant (WWTP) and 4.21 mgd treated, combined, at the Martinez facilities. All SARA plants are similar in design, relying on oxidation ditches for wastewater treatment. Two 2-meter Ashbrook Klampress Belt Filter Presses (BFPs), one each at the Upper Martinez and Salatrillo
WWTPs, provided dewatering for SARA solids, but additional capacity was required. The existing 2-meter belt presses were being pushed to their hydraulic limit at both plants, although solids loads to both units were well within acceptable ranges. Additionally, cake loading systems at each
plant required operators to stop pressing as soon as sludge hauling vehicles were filled, so that filled haulers could be moved and a new hauler put in place. The bottle-necks in the dewatering and loading were controlling solids wasting operations and, therefore, affecting wastewater treatment
operations as well. In short, SARA needed both additional hydraulic capacity and more efficient loading operations. Dewatering improvements recently constructed at two SARA plants provide an opportunity to compare two different solutions to hydraulic capacity issues: conversion of an existing
2-belt BFP at the Salatrillo WWTP to a 3-belt unit and the installation of new, alternative design 3-belt unit at the Martinez II WWTP. The differing solutions adopted at each plant reflected site-specific constraints and opportunities. This paper focuses on the relative merits of the two
dewatering solutions adopted, comparing capital costs, operational costs and issues, and BFP performance. Additionally, the impact of the improved cake loading system on SARA operations is discussed.
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