San Antonio Water System (SAWS), a public utility owned by the City of San Antonio, is responsible for providing water and wastewater services to over 2 million people across the region. Established in 1992, SAWS has been at the forefront of water management, striving to deliver high-quality services while addressing the growing demands of a rapidly expanding population. With a commitment to innovation and sustainability, SAWS continually seeks advanced solutions to improve its operations and serve its community better.
Facing clogs and delays
The utility’s initial septage receiving system relied on homemade screens that were designed as a temporary solution but, like many temporary solutions, had been in use far longer than anticipated. These screens struggled to keep up with the increasing volume and diverse type of waste being processed. The system often clogged, leading to long lines of waiting trucks and extended unloading times. The inefficiency of these homemade screens not only disrupted operations but also allowed grit and large debris to enter the treatment plant, causing significant wear and tear on the equipment and leading to frequent maintenance issues.
The challenge was compounded by the varied nature of the waste received, which included everything from household septage to waste from portable toilets used at large public events. This diversity in waste composition made it difficult for the existing system to function effectively, often resulting in operational bottlenecks and increased downtime.
The limitations of initial screening solutions
In an effort to address these challenges, SAWS initially focused on finding a grit screening solution that could be integrated into its existing process. They tested a demo sludge screening unit, hoping it would provide the necessary filtration. However, the demo unit quickly clogged due to the high volume of solids and diverse debris being processed. This failure highlighted the need for a more robust and comprehensive solution.
SAWS O&M Engineer Roland Gutierrez and his team conducted a thorough examination of the incoming septage and found an array of unexpected items, including knives, ammunition, power tools, clothing, syringes and electronic devices. These findings underscored the limitation of the demo sludge screening unit and the need for a more adequate screening solution.
A step forward
Based on the insights gained from the initial attempts, SAWS decided to implement three HUBER Ro 3 sludge screening units. These units are known for their screening durability and efficiency, which was the primary concern for SAWS. The implementation also aimed to automate the transfer process for delivery drivers, thereby reducing processing times and minimizing manual handling of waste.
However, the deployment of the units coincided with a city-wide celebration attended by over 1.5 million people. The event generated an unprecedented volume of waste, as a result, the units were overwhelmed by the sheer amount and type of debris, including large and hazardous items in the waste.
HUBER’s service team made several modifications to enhance the capacity of the screening units. Despite these efforts, the debris load was too significant for the units to handle the waste effectively.
The game changer
Recognizing the need for a more robust and versatile screening solution, HUBER recommended its RotaShield units to SAWS. The units are specifically designed to handle high debris loads and provide other benefits:
- Efficiency: The RotaShield units reduce delivery times from 15-20 minutes to less than seven minutes per truck. This improvement translates to substantial time and cost savings for both SAWS and the delivery companies.
- Maintenance: The design of the units virtually eliminates downtime associated with debris handling, ensuring continuous and reliable operations.
- Cleanliness and Safety: By minimizing manual waste handling, the units improve sanitation and safety at the septage receiving station. This is particularly important for maintaining a hygienic and safe working environment.
- Automation: The units enhance billing and tracking processes, providing better compliance and accountability. This feature is critical for managing large volumes of waste and ensuring accurate record-keeping.
The rotating perforated cylinder construction
The RotaShield units come in three sizes to handle flow rates from 400 to 1,200 gallons per minute (gpm). They are capable of offloading large 4,000-gallon vactor trucks in under seven minutes. Designed to protect screens and grit removal systems from debris typically found in septage, the units feature a rotating perforated cylinder with internal flights. The design transports debris while rinsing away organic material, eliminating common maintenance issues associated with traditional systems.
Traditional screens used for septage receiving often include tank-mounted, partially submerged rotary drum screens with internal troughs and augers. These designs can lead to downtime and maintenance issues, such as screenings hanging on the trough, wrapping around the auger, sediment lying in the tank, broken rake teeth, and bent bars. The design of the recommended units avoids these problems by eliminating the need for the tanks, troughs, augers, or seals.
Positive outcomes for SAWS
The implementation of the screening units transformed SAWS’s septage receiving process. The new system handles the high volume of waste efficiently, significantly reducing processing times and virtually eliminating downtime. The units separated large debris, inorganic solids and grit, ensuring smooth operations and high customer satisfaction.
The screening units’ ability to handle large and hazardous debris, such as that from city-wide celebrations, made them an ideal solution for SAWS. The units proved to be durable and reliable, handling the diverse and often challenging waste composition with ease.
In addition to improving operational efficiency, the units also enhance the overall experience for the delivery companies. The significant reduction in processing times means that trucks have to spend less time waiting to offload, which translates to cost savings and increased productivity for the delivery companies. The automation of billing and tracking processes further streamlines operations, ensuring accurate and efficient record-keeping.
“HUBER’s service, design, and implementation teams were tremendous during this process which, honestly, became frustrating for both camps,” said Roland Gutierrez. “But HUBER was relentless in its investigation into what was and was not working and persistent in putting the best solution for our quite significant waste processing demands in place.”
Innovation in action
These units have provided SAWS with a reliable, efficient, and low-maintenance solution for their septage receiving process. The transition to RotaShield has solved the initial problems and significantly improved overall efficiency and effectiveness of the system.
“We’ve gone from homemade dirty screens and long lines to clean, quick, practically hands-free automation. Companies that send their deliveries here are ecstatic. Even if you just calculate the time saved it is tremendous because five minutes instead of 15 to 20 is money for them,” Gutierrez said.
The partnership between SAWS and HUBER has resulted in an improvement in the septage receiving process, ensuring smooth operations and high customer satisfaction. HUBER’s experience and expertise in the field of liquid-solid separation technology made the company a partner for SAWS, demonstrating their ability to meet and exceed the challenges posed by modern wastewater management.
Gutierrez summed up the experience: “The way this happened is a huge rarity. In the 27 years I’ve been with the company [SAWS], overseeing countless projects and working with many vendors, this is one of just a handful of occasions where a manufacturer’s service and support teams took it upon themselves to make it right when they knew expectations—whether ours or theirs—weren’t being met.”
