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Design Considerations to Achieve Low Maintenance Water Treatment Systems

For industrial and remediation water treatment systems, long-term operational costs (OPEX) can vastly outweigh the initial capital expenditure – especially as the system approaches the end of its useful life. Unfortunately, and understandably, treatment system design tends to focus on the treatment efficacy and often neglects maintenance elements, which increase the total cost of ownership of your system. This article discusses some general design considerations which may minimize the operation and maintenance costs of water treatment systems.

Maintenance-minded Design

First, general equipment layouts should be designed with regular maintenance activities in mind.  Adequate space should be allotted around commonly maintained areas (motors, actuators, belts) and allow activities to be completed with “boots on the ground”. Pipe runs and equipment placement need to allow clear access to interior components (bag filters, air stripper trays, carbon, RO filter elements, for example). Instruments which need to be regularly calibrated (such as pH sensors) should not be located in elevated ducting or piping, and if instruments are in elevated situations, they should have a remote display easily monitored from the ground. For example, Anguil maintained a customer system that had a pH sensor in an elevated pipe run 10 feet off the ground. A simple three-point recalibration of this sensor required a man-lift rental and a second operator to read the calibration values off the control panel since a local LCD display was not provided on the pH analyzer. Many maintenance headaches can be avoided if an experienced operator and installation expert is consulted while the system is still on paper.

Peripheral Systems

Most water treatment systems require integration of several technologies to meet effluent treatment goals. For example, remediation of a LNAPL plume may require an oil-water separator, air stripper and carbon (GAC) adsorption system. However, peripheral systems are often added to protect the primary treatment equipment, maintain treatment efficacy, while lowering maintenance costs.

Grit and Large Solid Removal

Large solids and grit should be removed as early in the treatment process as possible. Removal of grit and large solids, often by a simple cone bottom tank, can reduce wear on pump impellers and valve seats, while also limiting clogging of sensor ports and filter media.

Scaling Control

Deposits, both organic and inorganic, can destroy a treatment system and require complete equipment replacement or major maintenance costs to return the equipment back to full functionality. Hardness scale (calcium, magnesium and silica) and iron deposition are the two most common inorganic culprits. However, others equally problematic, but industry-specific such as struvite in landfill leachate systems, can be encountered. Neglecting scaling potential can increase filter changeouts, instrumentation maintenance, clog spray heads and injection ports, cause cementing of filter and packing media, and sometimes result in complete pipe blockage. Controlling scaling potentials can be done with softening (or ion exchange), reverse osmosis, precipitation, sequestration and pH control.

Bacterial Growth Disinfection

Bio fouling from bacterial growth can quickly gum up a system and is often disregarded during the design process. Bacterial growth can clog filters, foul carbon systems, encumber pipes and blind off membranes and can be controlled by direct disinfection or by discoursing growth from the outset. Disinfection can be accomplished by the addition of chlorine, sodium hypochlorite, chlorine dioxide and biocides. However, many disinfection systems bring unique challenges in terms of chemical handling, health and safety and disinfection byproducts. Long-term management and removal of existing bio scum can be accomplished by bio dispersants, which remove food sources, weaken cell walls and inhibit bacterial reproduction. Bio dispersants are typically safer to handle than biocides or corrosive chemicals.

Preventive Maintenance Plan

Lastly, a preventative maintenance plan should be in place from day one of system operation. The plan should include a complete schedule of mechanical, electrical and controls checks. Mechanically, all moving parts need to be checked for wear and tear, pump alignments should be verified, seals and gaskets should be checked for integrity, leaking tanks identified, and all process equipment checked for inorganic and organic deposits. Electrically, all control signals should be verified, control panel components should be operating correctly, including all system switches and control buttons. Finally, all system alarms should be checked, the sequence of operations validated and all instruments properly calibrated.

Performing regular and routine maintenance keeps small problems from becoming maintenance nightmares and inflating your operation and maintenance budget beyond acceptable levels. Taking maintenance into account during system design can minimize operational costs, maximize up-time and keep you focused on your core business.  

Article contributed by Anguil Environmental Systems Inc.

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