Are your tank components beginning to show their age? While functional, it might be time to consider an upgrade. Realizing there isn’t much room in the budget, what three components should you choose? 

Certainly there are numerous factors to consider when making your decision – greatest need probably tops the list. What you choose also depends on where you draw your water – surface ponds or aquifers, as well as plant size and even geographical location. 

Rick Garloff, operator with Tidewater Utilities in Rehoboth Beach, Del., says a welded storage tank, mixing system and geodesic dome are three components that would make his list, while Rob Gray, distribution facilities superintendent for the Chester Water Authority in Chester, Pa., would consider a roof hatch, mixing system and welded storage tank, as well as a flange outlet and safety railing. Here are some tank components to consider for your next upgrade: 

1.     Tanks

As an operator with Tidewater Utilities, Garloff is responsible for nine small facilities serving 176,000 customers. The utility draws water from wells and has a distribution system that includes two new, above-ground storage tanks (300,000 and 750,000 gallons) with a third on the way. Garloff’s current tanks are bolted and sealed, but he says a welded tank might be worth considering. “I wouldn’t see any problem with a welded tank versus a bolted tank, so I would say, yes.” 

Gray, whose storage facilities can hold up to 106 million gallons of treated water, approximately a three-day supply, would agree. “Really, the only two types of tanks we have in the Chester Water Authority are concrete tanks and welded steel storage tanks. Bolted I would advise against because of leakage,” he says. A flange outlet also would make Gray’s list. “The way a tank functions, you would have an inlet, you would have an outlet and you would have an overflow. The outlet would be below the ground to prevent freezing and that would be flanged.” 

Here are some tank options to consider: 

• Fisher Tank Company’s welded steel above-ground storage tanks and standpipes, constructed on site, are designed and fabricated to AWWA D100 standards. Tanks can be designed to include aeration and mixing systems, ladders and handrails, exterior piping, and other systems and appurtenances as dictated by the site, weather conditions, water usage and other factors. The tanks offer flexibility in design, exterior painting colors, patterns and images, and future modification options. 
• The integrally molded flange outlet (IMFO) from Poly Processing is a seamless, molded-in flange that’s part of a strong polyethylene tank that preserves the hoop integrity or the structural component of a vessel. Not only is the threat of crack propagation from mechanical fittings or inserts eliminated, the flange tooling is placed at the bottom sidewall, maximizing tank volume through a full drain. This allows all maintenance to be performed outside the tank.
• Tank Connection offers online tools that make it possible to select and specify a tank in less than five minutes. Capacity calculators are easy to use and have become the industry standard for quick reference. Specifications for AWWA D103, AWWA D100, FM, API and FIELD-WELD tanks may be downloaded and customized for customer needs. Reference designs for RTP bolted construction, shop-weld and field-weld construction are available. 
• The ZICKERT Shark from WesTech Engineering offers rectangular tanks and lamella plate clarifiers for drinking water purification plants based on the forward and return movement of hydrodynamically designed rake sections. The concave faces of the sections transport the sediment toward a sludge pit. During return movement, the wedge-shaped parts of the sections slide under the sludge blanket, providing continuous and unidirectional transport. The robust and simple design has few moving parts, can be powered by hydraulic or electric motors, and provides the same results whether it is pulled or pushed. It is also easy to install and maintain, offering complete sludge transport without dead zones or turbulence.
• Shop- and field-erected tanks for clarifiers and thickeners from Hi-Tech Environmental Inc., A Division of Kusters Water, can be manufactured in accordance with API-650, and custom designed to suit each customer’s needs. The tanks are available in carbon and 304 and 316 stainless steel. 
• Husky Portable Containment bladder tanks are available in sizes from 25 to 50,000 gallons, and are constructed from XRs, PVCs and military-spec urethanes. All hardware is stainless steel. Bladders include access panels, maneuvering straps near the corners and every 5 feet down the sides, flame arrestors, double “T”-style vents and mushroom vents. Storage bags and field repair kits are included. Ground covers and sunscreens in various weights are optional.
• Defender tank covers from Environetics are custom-manufactured to fit new or existing potable water tanks. Odor control covers contain volatile organic compounds at their source. 
• International Paint’s Devoe Bar-Rust 234P is a solvent-free epoxy, low-temperature potable water tank lining system designed to meet the industry’s need for low VOC compliance. The 100 percent solids, high-build water tank lining system can be used for new construction and rehabilitation installations. It has a fast cure time, 2:1 mixing ratio, and single coat application capability – even in temperatures as low as 35 degrees F. It carries an NSF/ANSI 61 certification for potable water use and cures to a hard, high-gloss finish for a safe, clean and maintenance-free installation. The system is applied with a plural airless sprayer directly to the water tank’s carbon or stainless steel interior. 

2.     Mixing systems 

Named the 2011 Water Operator of the Year by Delaware Technical Community College for his technical excellence and exemplary work ethic, Garloff says a mixing system could be a helpful upgrade. “Any kind of mixer that you can put in your system would definitely help with your water quality,” he says. “It would give you a good mix of chemicals, which would reduce your contact time and give you a better result earlier.” 

Gray says a mixing system also would make his list. “Not all water tanks require a mixing system, but it’s good for water quality in some cases, and it’s also good for freshwater entering the tank and freshwater exiting the tank. In other words, the tank doesn’t short-circuit with the mixing system in place,” he says. “If you have a common inlet and outlet pipe and the water is being pumped into the tank, the water would tend to stay near that penetration and be the first water out of the pipe. The water that is farthest from the inlet pipe would just stay there without a mixing system.” 

Consider these mixing systems: 

• Caldwell’s TAP-APP air pulse protection mixing system is an active mixer that utilizes pulses of air to mix potable water storage tanks. The system incorporates both active and passive technologies to produce consistent and thorough mixing while using no moving parts or requiring maintenance within the water container. Air pulses are calibrated during installation to ensure complete tank mixing according to tank size and style, while mixing cycles are scheduled according to the specific mixing needs and around daily peak energy periods. This technology reduces typical tank mixing times, even in tall or large-capacity tanks. 
• The Silo Discharger from Sodimate ensures a smooth discharge of dry chemicals while mixing the product to ensure a consistent blend in water treatment applications. The unloader rotates within the container bottom to prevent non-flowing materials from jamming and bridging. The discharger is designed for difficult dry chemicals such as lime, powdered activated carbon (PAC) and soda ash. It also can integrate up to four volumetric screw feeders, with each screw feeder totally independent and capable of up to 15,000 lbs/hr with different lengths and throughput variations. 
• The Tank Shark management system from Process Solutions can provide real-time water samples and automated chlorine and chloramine injection to maintain required levels while mixing the tank. The system can manage the addition of on-site generated hypochlorite, bulk hypochlorite, gas chlorine or aqueous ammonia. Aeration is also available to reduce VOCs, which in turn, lower TTHMs. The system has no mechanical or electrical components inside the water storage vessel, and installation doesn’t require penetration in the tank or for the tank to be taken out of service. This system is SCADA-compatible. 
• The Trihalomethane Removal System (TRS) from PAX Water Technologies is an aeration system that reduces THMs in water storage tanks. By using sprayers, surface aerators, tank mixers and performance modeling software, TRS is able to maximize effectiveness while reducing energy costs. 

3.     Domes and roofs 

Garloff says a geodesic dome might be another component he’d consider. “We don’t have a lot of snow here, but it would be a good upgrade from a maintenance perspective.” 

Gray says a roof hatch would be his choice for gaining access to the interior of a tank, as would a safety railing. “The older tanks, as they get rehabbed, we make sure we have safety railings by the roof hatches and by the ladders on the exterior to make it safe.” 

Here are some options to consider if your plant’s domes and roofs are due for upgrades: 

• The OptiDome from CST Covers is a flush batten aluminum geodesic dome that features a double web I-beam for strength and stability, plus batten seal technology that eliminates environmental exposure and UV degradation. Hub cover technology removes the need for exterior sealant at the nodes, eliminating routine maintenance and inspection requirements. The enclosed gasket design protects from UV and sealant degradation, reduces sealant use, and eliminates ponding. It is compliant to Euro-Code, Aluminum Association Design Manual 2010 and International Building Code 2012. 
• HMT’s Geodesic Dome Roofs are custom-engineered to accommodate a range of shapes, spans and operating service conditions. They can be designed to accommodate special loading and design conditions, specifications and requirements. Ideal for both new tank construction and retrofits, the roofs are fabricated from high-strength, corrosion-resistant aluminum alloy materials. The structure is designed to be clear span and self-supporting from the tank shell, eliminating the need for internal supports. 
• The Bilco Company’s enhanced-performance roof hatch is designed for buildings seeking LEED certification and for those located in areas with extreme temperature conditions. It meets LEED standards for recycled content, and features a cover and curb that are fully insulated with a 2-inch polyisocyanurate thermal insulation board. The cover features an EPDM finger-type gasket that ensures a positive seal with the curb to reduce air permeability and ensure energy performance. It has been tested and approved to BS EN standards for weathertightness, sound rating and security. It is fabricated from aluminum, and features counter-balanced lift assistance for one-hand operation. 
• Key Lite safety rail systems from Kee Safety are constructed of high-grade aluminum silicon magnesium alloy for strength and corrosion resistance, and are OSHA-compliant. They are easy to install, requiring only a hex tool and pipe cutters. The lightweight components feature smooth contours and recessed set screws for an aesthetic appearance, and are designed to fit 1- to 2-inch Schedule 40 pipe sizes. The system is a pipe-fitted structure connected by a variety of Kee Lite safety components. The railings can be installed for use inside or outside, and the modular design allows for reconfiguration. 

(All equipment listings from WSO Product Focus, March 2013.)