These specialized pumps assisted one company in developing a new water disinfection device for municipalities.

Several North American government agencies and organizations share the responsibility of protecting the public’s health and safety while serving the best interests of water treatment facilities. Most water treatment facilities recognize that environmental protection is not just the responsibility of government agencies and organizations. In fact, most municipalities use the governmental regulations as guidelines to establish and maintain their own basic standards as best practices for water safety.

Ferrate Treatment Technologies LLC (FTT) works with municipalities to follow such best practices. To complete a new water disinfection device’s design and meet the safety needs of municipalities, FTT partnered with a progressive cavity pump manufacturer that offered specialized metering pumps for their chemical handling challenges. Chemical metering pumps are actually not required to be National Sanitation Foundation (NSF) certified in disinfection systems, but as a critical component of a water treatment system process, pumps often come under careful scrutiny because they meter chemicals that could be harmful if not handled properly.

Many objectives came into consideration, mainly meeting the governmental laws and regulations affecting drinking water processes. Deciding what type of pump technology to install for water and wastewater treatment applications can be a daunting task.

Government Regulation

Fully automated water treatment systemA fully automated water treatment system produces ferrate, a chemical generated onsite at water treatment facilities. (Images courtesy of seepex)

The U.S. Environmental Protection Agency (EPA) is responsible for maintaining and enforcing water pollution prevention under a variety of environmental laws. The EPA has sanctioned other organizations like NSF International that have common interests and goals. NSF provides standards development, product certification, testing, auditing, education and risk management services to the public. NSF is accredited by the American National Standards Institute (ANSI) to develop American National Standards for the safety of all materials and products that treat or come in contact with drinking water, such as plumbing components, water treatment chemicals and drinking water filters. ANSI is a private nonprofit organization that oversees the development of standards by representatives of other standards organizations for products, services, processes, systems and personnel in the United States.

In 1990, the EPA replaced its own drinking water product advisory program with NSF/ANSI standards. The NSF mark on any product affiliated with drinking water treatment processes means that the product complies with all standard requirements and ensures water industry stakeholders that the product will not create adverse effects on the health of those consuming the drinking water or on the environment.

NSF/ANSI 61, titled “Drinking Water System Components—Health Effects,” sets health effects criteria for water system components. Forty-eight states currently require NSF/ANSI 61 compliance of any product that is manufactured, sold or distributed for water treatment and comes into contact with drinking water.

Drinking water system components fall into two categories of regulation. Centralized water treatment plants and water distributions systems up through the water meter are typically regulated by state drinking water agencies. Water distribution systems downstream of the water meter or inside a building are typically regulated by state or local pumping codes.

Types of products requiring NSF certification include:

  • Protective barrier materials like paints or coatings
  • Joining and sealing materials such as adhesives
  • Mechanical devices
  • Water meters or valves
  • Plumbing and piping related devices
  • Nonmetallic potable water materials

This is essentially every component of a water treatment system. However, the EPA’s Safe Drinking Water Act guidelines for drinking water treatment plants do not require NSF compliance for all mechanical chemical feeders. This is because feeders do not come in contact with finished drinking water or post-treated water in the distribution system.

Water treatment system using progressive cavity pumpsThe water treatment system uses progressive cavity pumps to reliably meter feedstock chemicals.

Metering pumps are used as feeders primarily to deliver precise dosages of chemicals to the pretreatment process. NSF 61 Section 8 further provides a guidance of “high rate feeders,” a category that includes metering pumps, and states a minimum ratio allowance calculated based on an area of the wetted surfaces to a specific volume of water treated. This allows the exemption by a waiver allowance of appropriate diluted surface area (DSA) ratio calculation meeting a specific threshold level. Metering pumps qualify for exemption with the DSA ratio calculated per a design’s flow rate for a specific plant flow throughput. However, many facilities require all parts of their treatment systems, including their metering pumps, to be constructed of NSF-certified components as part of their own best practices regardless of this omission.

Case Study

Ferrate Treatment Technologies LLC (FTT) follows such best practices. Based in Orlando, Florida, the company was founded to invent, develop and commercialize water and wastewater treatment technologies based on its proprietary iron chemistry platform. FTT manufactures a water treatment system that produces ferrate, a water treatment chemical generated on site at water treatment facilities. Ferrate is synthesized in a temperature-controlled reaction using commercial-grade chemical feedstocks.

When dosed into water as a liquid, ferrate acts simultaneously as a disinfectant, oxidant and coagulant and destroys most micro-organisms. These include inactivate micro-constituents such as endocrine disrupting chemicals (EDCs) and pharmaceuticals and personal care products (PPCPs). For municipalities requiring total NSF compliance, every component of FTT’s water treatment innovation had to comply with NSF/ANSI 61 standards, including the chemical metering pumps.

FTT needed a pump technology that was both NSF/ANSI 61 certified and capable of reliably and precisely metering and blending the feedstock chemicals needed to produce ferrate. Several types of hose and diaphragm pumps are NSF-certified, but the company found that these pump types did not meet their requirements for consistent blending, steady flow and corrosion resistance.

The initial design of FTT’s water treatment system included diaphragm pumps as the main pumping elements. However, pulsation and blending issues proved to be a problem. The diaphragm pumps were complex and prone to breakdowns. Vapor lock and valve leaks required expensive and time-consuming repair kits.

Water treatment systemThe water treatment system

FTT replaced three diaphragm pumps with progressive cavity pumps (PCPs), which provided better blending and flow control. The PCP design offered several advantages over other positive displacement pumps, primarily the simple principle of the pumping element, which employs a metal rotor and a rubber stator. The rotor rotates inside of the stator, forming two cavities at the suction end of the stator. One cavity closes as the other opens, and the cavities progress from one end of the stator to the other. The result is continuous flow streams with relatively low pulsation. This provides accurate metering results and a better ratio of blending chemicals, as opposed to over- or under-feeding with a diaphragm pump.

Another major benefit is that the sealing line between the rotor and stator acts like a valve. This eliminates the need for a flow control valve. Additionally, the compression fit between the rotor and stator prevents siphoning and back flow, a concern in water treatment. This results in tighter control, less residual byproduct and less chemical usage over time.

The PCP design was more compact, with lower maintenance and personnel requirements and lower operating costs. No pulsation dampeners were needed. Other benefits included low shear rates, run-dry and overpressure protection, and no vapor lock. The PCPs also had components made of specialized materials just for chemical processing that resist wear and hold up in caustic environments.

Finding a properly certified PCP was still difficult. Although chemical feeders are not required to be NSF-certified, many of FTT’s potential end users wanted a system entirely composed of NSF-certified products.

At FTT’s request, one progressive cavity pump manufacturer answered the need for NSF/ANSI 61 certified progressive cavity metering pumps. The process of certification took nearly four years. It included physical audits of the manufacturing facility, which will continue annually to allow verification of proper labeling and record keeping, quality assurance, and sample collecting for subsequent testing.

Certification also required pump and component material formulation and ingredient disclosure. Pump part suppliers had to be investigated. Testing of the pumps with the actual chemicals used in treatment processes as well as testing on the actual pumped materials for toxicity, leaching and contamination was required.

NSF/ANSI 61 Certification

The National Sanitation Foundation offers a certification process for NSF/ANSI 61, or “Drinking Water System Components—Health Effects,” compliance. According to the foundation’s website, the process includes the assignment of a NSF project manager to guide companies through certification. The website also lists the seven steps of the certification process:
  • The company submits an application.
  • Product formulation, use and toxicology information are provided.
  • The NSF toxicology department reviews the formulations.
  • NSF reviewers perform a plant audit and sample collection.
  • An NSF laboratory tests the sample collection.
  • A final toxicology evaluation is completed.
  • NSF certification is granted for compliant products, and the NSF mark can be used on products, packaging and marketing materials.