Structured-sheet media helps meet strict nitrification standards

Problem: The City of Stockton, Calif., needed to upgrade its 55 mgd wastewater treatment plant to meet NPDES regulations for tertiary treatment. The goal was a reliable, economical technology that would achieve tertiary nitrification, especially during winter. Because of the plant’s location, seismic hazards had to be considered.

Solution: After a comprehensive evaluation, nitrifying trickling filters were selected based on low energy consumption, process stability and operational simplicity. High-density structured-sheet media from Brentwood Industries proved cost-effective for achieving optimal nitrification. The media modules yield a high specific surface area and are built to a tight deflection standard of 1 percent, allowing maximum treatment capacity within a small footprint and meeting strength requirements. Two nitrifying towers were built, each 166 feet in diameter with a media depth of 22 feet. The towers began receiving effluent from oxidation ponds and engineered wetlands, designed to decrease solids loading and maintain stable ammonia loading. From there, effluent was discharged to a dissolved air flotation tank and tertiary filter for polishing.

Result: The trickling filter installation allowed the plant to maintain an ammonia removal rate consistently in excess of 94 percent, meeting the required ammonia discharge permit of 2 mg/L. 610/374-5109; www.brentwoodindustries.com.

Fabric building provides efficient sludge bed cover

Problem: In the past 10 years the population of the Village of Huntley, Ill., has increased from 6,000 to more than 23,000. The village uses two activated sludge wastewater treatment plants, where solids are processed and dewatered. Without covered storage space, the material was stored in beds exposed to the elements. “We get charged by the cubic yard,” says utilities superintendent Steve Zonta. “By storing it without cover, it would get rained on and grow in mass.” 

Solution: The team chose a Hercules Truss Arch Building. “I saw a ClearSpan catalog, spoke to a truss arch sales specialist, and realized that a fabric structure would be a cost-effective way to solve our problem,” says Adrian Pino, chief wastewater operator. “We already had a wood structure with a metal roof at the East Wastewater Treatment Plant, and the structure we chose came in at less than a third of what the other structure cost.”

Result: With a 77- by 96-foot building, the village can now store up to 13,000 cubic yards of material under cover. “The warranty and the fact that the building could be engineered to specific snow and wind loads were important,” says Pino. “It proved that this wasn’t going to be just a temporary solution.” 866/643-1010; www.clearspan.com.

Bolted tanks provide storage solution for Oklahoma town

Problem: Steady population growth in Monkey Island, Okla., put a strain on the water treatment plant as it struggled to meet demand and new federal regulations. The Grand Lake Public Works Authority commissioned a newer, more efficient system that would pump water from six freshwater wells into storage tanks.

Solution: The utility, which serves 1,400 residential and 200 commercial customers, awarded the project to Texas Aquastore and CST Industries. They installed a 500,000-gallon HydroTec tank constructed of panels overlapped and bolted into place to prevent leakage. Systems are manufactured in ISO 9001:2008 certified facilities. To ensure no leakage, each panel is dry-powder epoxy coated using an Opti-Bond Coating System. A performance urethane is applied to the exterior to extend gloss and color retention. The tank was installed from the top down using jacks, so no high scaffolding was required.

Result: Installation took less than two weeks. The cutover to the new water treatment plant will be completed by spring 2015. “When they said, ‘Your tank’s here,’ I went out and looked and saw these boxes,” says Jim Anderson, manager of the authority. “I was amazed at how they assembled the tank from the individual panels. There was no hassle, and the crew did a great job.” 800/421-2788; www.cstindustries.com.

Coating provides protection for iconic water tower

Problem: Turning an unimpressive elevated water storage tank in Silvis, Ill., into a landmark that resembles a golf ball on a tee was a logistical and creative challenge for the project’s coating contractor, Jetco. The project aimed to elevate the city’s profile as the site of the annual John Deere Classic golf tournament. Once the art was complete, it would need protection from the elements.

Solution: The exterior artwork required experienced applicators to calculate the ratios and proportions of 4-foot-diameter circles shaded to resemble the dimples on a golf ball. Long-lasting, high-performance coating systems were specified to extend the project’s maintenance cycle. A zinc-rich urethane prime coat, a polyurethane intermediate coat and Tnemec’s Series V700 HydroFlon low-VOC fluoropolymer coating provided UV light resistance and high color and gloss retention.

Result: Since its completion, the Silvis water tank has attracted extensive national and international media attention during coverage of the PGA golf event. It has also been featured on regional TV stations, CNN and in numerous newspaper and magazine articles, and it was voted a finalist in the 2013 Tnemec Tank of the Year contest. “I think it gives us an identity,” says Silvis Mayor Tom Conrad. “It gives us a source of pride. We have something that no one else has.” 800/863-6321; www.tnemec.com.

Polyurethane coating stops hydrogen sulfide damage

Problem: Hydrogen sulfide corrosion was destroying the concrete tank walls at the wastewater treatment facility in Altoona, Pa. A flexible, durable coating was needed to prevent further damage to the two 60- by 24.5- by 11-foot tanks, plus several additional square feet of old, pitted and rough concrete. The work had to be done in a confined space and in accordance with the facility’s safety protocols.

Solution: Because a long-lasting coating with a smooth finish with high chemical resistance was important, the facility chose Hi-Chem PW from Rhino Linings Corporation. The elastomeric polyurethane formulation has a rapid cure time and good elongation properties and is NSF/ANSI 50 and 61 certified. Before installing the coating, the concrete substrate was checked for chloride and pH levels. Next, a neutralizing solution was applied, and the surface was pressure-washed. Concrete gaps and bug holes were patched with a fast-curing polyurethane caulk, and the entire surface was coated with Rhino Primer 251 at 180 to 200 mils. Periodic thickness measurements were performed using ultrasonic and analog methods. Hi-Chem PW was applied at 250 mils to seal the walls and stop the damage.

Result: One tank was coated in November 2007, and the second in February 2009. Both are still operating with no corrosion issues. 800/422-2603; www.rhinoliningsindustrial.com.

Application of coagulation principles overcomes clarifier startup issue

Problem: During the recent startup and commissioning of a new water treatment plant in Turkmenistan, the RO feed had high silt density index (SDI) values. The treatment process passed river water at 8 mgd through solids contact clarifiers, gravity filters, reverse osmosis (RO), and cation, anion and mixed-bed exchanger systems to supply water to a fertilizer plant. Leaders hypothesized that the very low TSS concentration did not allow charge destabilization via coagulation.

Solution: Doosan Hydro Technology solids-contact clarifiers, designed for 70 mg/L maximum TSS, were only seeing 6.0 mg/L. Using operating parameters defined by jar testing, the clarifiers were operated at an elevated pH of 9.5 to 10, with ferrous sulfate coagulant at 50 mg/L, polymer at 0.6 mg/L and an upstream chlorine dose of 2.0 mg/L. However, the clarifier/gravity filter combination resulted in RO feed water with readings of 5.5 to 6 SDI, above the target of less than 4 SDI. Although the jar tests at the operating conditions indicated good TSS settling, the results could not be replicated by the clarifier/filter combination. Settling of TSS/colloids in the jar tests occurred due to sweep flocculation at a relatively high coagulant dose. The colloids were swept by coagulant metal oxides/hydroxides formed at high pH (and in presence of chlorine in this case to convert the ferrous-based coagulant to ferric). The sweep flocculation was likely not as effective in the relatively more turbulent clarifier conditions, and the excess hydroxide carryover fines deteriorated clarifier/filter performance.

Result: By reducing the coagulant dose to 20 mg/L and removing polymer altogether, the desired SDI goals were exceeded, with final SDI values of 1 to 2 after the filters. 813/549-0182; www.doosanhydro.com.

Product improves total solids destruction in aerobic digester

Problem: The operators in an east-central Missouri city wanted better digester performance in the cold months. Colder months mean low volatile solids destruction and frozen soils that don’t allow land application of biosolids. The team wanted better settling, increased decant and more space within the digesters.

Solution: After six months of trials, the operators discovered that BIO ENERGIZER from Probiotic Solutions could accelerate the rate of endogenous respiration by improving cell wall permeability, thus increasing biomass metabolism and reducing volume.

Result: The product created nearly 85 percent volatile solids destruction in 27 weeks and improved decants. It led to greater digester capacity, better settleability and decants, and better overall aerobic digester operation. 800/961-1220; www.probiotic.com.

Compact, lightweight fiberglass baffles used for underground treatment

Problem: The Lima (Ohio) Wastewater Treatment Plant, a 33 mgd tertiary facility, needed to expand its capacity. One solution was to use a baffle wall system that would slow the flow of water, improving primary sedimentation. The installation would need to be completely underground.

Solution: Baffle wall panels were transported to their underground locations through 36-inch manholes to reach the primary clarifiers. Harrington Industrial Plastics recommended Strongwell’s FRP due to its baffle panel size, high corrosion resistance against wastewater and shipment flexibility. The lightweight (6 1/2- pound-per-foot), 24-inch baffle wall panels were easily transported through the manholes.

Result: Peterson Construction, the contractor, found the installation relatively easy without the use of cranes or other lifting equipment. EXTREN Series 500 12- by 6- by 1/2-inch I-beams and 3- by 3- by 3/8-inch equal leg angles were also used as baffle supports. 276/645-8000; www.strongwell.com.