Greg Knows Water

When you hear the word membrane, most residential dealers think about under counter reverse osmosis (RO) processors. There is so much more to membrane separations than just the filter in the kitchen. The various separation technologies can augment products and services  offered to customers.

While the concept of separating ‘things’ from fluids remains unchanged, new technologies are bringing excitement to the membrane separation industry. While there are many exciting possibilities to explore, technologies with an immediate benefit to the residential dealer will be the focus.

Potential applications

Residential water treatment dealers can leverage the latest membrane separation technologies to help clients achieve better water quality. Choosing the correct membrane separation technology requires some basic information:

What is the water quality challenge that I’m facing? Test the influent water carefully for the following contaminants at a bare minimum:

• • • Hardness
    • TDS
    • Total alkalinity
    • Chlorine
    • Iron
    • SDI
    • Silica

Additional testing might be required, depending on the specific application or on test results on the above contaminants.

Additional questions

What is the water going to be used for?

Depending on the application, you might need additional pre- or post-treatment.

What service flow rate is required?

Membrane separation technologies will significantly reduce the delivered flow of water, so plan accordingly to balance processor speed and storage tank space.

How much raw water pressure and flow are available for processing?

These criteria are frequently overlooked when designing systems and are probably one of the main reasons for system failure. Ensure that you have sufficient flow and pressure available to drive the process. If not, necessary retention and pre-pressurization stages must be integrated into the holistic design.

How much space do I have available?

The slower the system, the more storage space is required to maintain a uniform delivery rate. Don’t discount the value of walls and ceilings when evaluating space available for equipment installation.

What drainage capacity is available onsite?

Most membrane separation installations will be configured in cross-flow or intermittent flow drainage modes. An adequate drain is required to ensure the discharge water can be handled in an environmentally friendly and code-compliant manner.

What electrical supply is available onsite?

Pumps consume significant amounts of electrical energy. Certain pumps might require higher voltages or three-phase supply. Make sure to  match the equipment to what is available at the home .

What piping material is to be used for product water distribution?

When integrating whole-house membrane separation technologies that will decrease TDS to less than 150 ppm or lower and pH to 7.3 and below, studiously avoid cupric or ferrous piping components and fittings, or take appropriate measures to balance pH and mitigate low TDS corrosion concerns.

Is the water microbiologically safe?

HPCs and pathogenic bacteria can colonize membrane separation equipment Steps should be taken to minimize contamination during water processing and storage.

Based on the above data, it will be relatively simple to work with OEMs or distributors to size and select the proper technology for the job.

Technologies to explore

Reverse osmosis (RO)

Under counter RO has become commoditized and is now as common as an icemaker filter. A large, untapped market lies in whole-house RO market to properly integrate equipment. 21^st century RO technology emphasizes low driving pressure and enhanced water efficiency – factors that are encouraging more dealers to install this technology in customers’ homes. Whole-house RO is most commonly used on high conductivity waters, or when a client is particularly health conscious and wants ‘the very best’ for their home. RO membranes are sensitive to scaling from hardness and silica, so chemical sequestration, ion exchange softening or even scale control technologies should be incorporated as pretreatment to prolong the lifespan of the membrane elements

Nanofiltration (NF)

Nanofiltration is a relatively recent development in the membrane market and is very useful to the water treatment professional who is interested in lowering TDS, clarifying water or orchestrating truly salt-free softening. Nanofiltration elements are usually available in 50  90 percent TDS reduction options, with a generally proportional amount of hardness reduction. Nanofiltration elements address certain high molecular weight aqueous salts as well as suspended and dissolved solids in the 0.001 to 0.1 micron range. Care should be exercised when integrating NF as a salt-free softening system, since the rejected calcium carbonate will scale aggressively throughout the drainage system unless a suitable cleaner is incorporated as part of the overall design. Many dealers are starting to incorporate nanofiltration into their product offerings, especially for homeowners who need to physically remove hardness without dealing with chloride discharge. Nanofiltration is also showing great promise in removing high molecular weight organics from water.

Ultrafiltration (UF)

Ultrafiltration is a coarser form of separation, suitable for separating certain colloids and suspended solids in the 0.1 to 5 micron range. UF is well suited for addressing bacteria, virus and colloids. While UF is a membrane technology, it can also occur in tube or hollow-fiber configurations, which open a number of creative opportunities to serve your client better. I personally prefer hollow-fiber ultrafiltration for residential applications, as it can operate with intermittent forward and back flushing and have a longer element life than spiral-wound technology.

Case studies

Take the time to research membrane separation and learn the nuances of these exciting technologies; it will be very rewarding to customers.

A pet peeve about most articles in trade journals is there aren’t enough real-life examples of how to implement what the author pontificates about. Here are some actual configurations of whole-house residential systems utilizing liquid separation technologies.

Ultrafiltration case #1

Customer moved into a new home in the city. Although city water was supposed to be completely safe, the customer wanted peace of mind concerning potential bacterial contamination, while also removing hardness, chlorine tastes and odors from the water.

Ultrafiltration case #2

Customer was concerned about hardness, iron, tannins and potential bacterial contamination.

Ultrafiltration case #3

Customer was concerned about trace hardness, suspended solids and potential bacterial contamination on a free-flowing spring.

Reverse Osmosis case #1

Customer was concerned about high hardness, high sulfates, high conductivity and unpleasant ‘musty’ odors in water. Noise and electrical consumption constraints necessitated the utilization of a quad 4×40 filtration array with low energy/high flux membranes, delivering an aggregate permeate flow rate of 2gpm to the storage tank.  High water hardness and bacterial concerns required periodic injection of an acid-based disinfecting cleaning agent. Electronic controls for the reverse osmosis array coordinate intermittent chemical injection as well as periodic membrane flushes to maximize usable service life.

Nanofiltration case #1

Client was concerned about water harness, but didn’t trust scale control technologies and felt that a softener was environmentally unsustainable. This was a municipal (city) water project. A custom NF element was fabricated for an 8” housing to maximize product flow at a delivered pressure of 80psi. Electronic controls for the nanofiltration element coordinate intermittent chemical injection as well as periodic membrane flushes to maximize usable service life.

The water that most of us drink is stored, treated and distributed to our homes by public and private water utilities.   Algae, bacteria, fungi and viruses can often be found in untreated water.   Americans have grown to expect a safe drinking water supply, but achieving that level of safety is a complex task.

One hundred and fifty years ago, much of the USA’s water supply was teeming with various forms of aquatic organisms. Waterborne diseases, such as cholera, typhoid, and dysentery, were a serious health problem, and they are still major concerns in third-world nations where over a billion people lack clean drinking water and almost two billion lack adequate sewage systems.   In 1992, the World Bank rated drinking water as first on its list of preventable environmental hazards worldwide. Since 1991 the largest cholera epidemic in recent history infected over 800,000 people from Peru to Mexico.

Waterborne microorganisms include coliforms and heterotrophic bacteria, viruses, and protozoa. These organisms range in size from extremely small viruses to relatively large cysts. They also vary greatly in the nature of their structure, lifecycle, and reproduction characteristics. Pathogenic microorganisms occur naturally in lakes, streams, reservoirs, and most surface water sources. Groundwater supplies are now becoming a subject of increasing concern, because enteric viruses and other organisms can leach into the groundwater system from the land application or burial of sewage sludge and other treatment wastes.

Since water utilities first began using filtration and disinfection systems a century ago, the risk of disease from drinking water in first-world countries has been greatly reduced. Despite the significant progress that has been made, there are still numerous disease cases resulting from contaminated drinking water in the United States. Health risks from aquatic pathogens range from mild gastrointestinal distress to systemic disease and, in severe cases, even death.

There are nearly 250,000 public water supply systems in the United States, serving everything from the smallest towns to major metropolitan centers. Ninety percent of the population receives its water through these community water systems, with the rest using private wells or other individual sources.  The United States Environmental Protection Agency (EPA) ranks drinking water pollution as one of the top four environmental threats to health. From 1971 to 1988, there were nearly 137,000 cases of waterborne disease–or an average of 7,600 cases per year–reported in this country. It is suspected that there were numerous undocumented cases as well, because many cases of gastrointestinal illness are not recognized as part of a larger pattern of waterborne disease. It has been estimated that only half of waterborne disease outbreaks in community water systems and about one third of those in non-community systems are ever detected, investigated, or reported. Microbes in tap water may be responsible for as much as one in three cases of gastrointestinal illness in the United States. Rates of waterborne illness as high as 900,000 cases and 900 deaths per year have been estimated by the Natural Resources Defense Council.

In the nineteenth century, progressive American communities began to separate the drinking water delivered to users, from household and industrial wastes discharged into sewage water systems. Many people in developing countries still do not have completely separate drinking water and sewer systems. Water utilities in the USA began treating drinking water with chlorine in 1908.

Chlorine and its compounds are currently used by over 98 percent of all U.S. water utilities that disinfect drinking water; It is a cheap and efficient killer.   By adding chlorine and its compounds to drinking water, almost all organisms living in the water are killed.   Chlorine remains in the water as it is distributed to homes and businesses, thereby retaining much of its ability to continue killing.

Although chlorine’s disinfectant value has been known for nearly a century, the mechanism by which the compound kills or inactivates microorganisms is still not completely understood.

The municipal water treatment process involves a series of different steps. Some of the major steps include flocculation and coagulation (the joining of small particles of matter in the water into larger ones that can more readily be removed), sedimentation (the settling of suspended particles in the water to the bottom of basins from which they can be removed), and filtration (the filtering or straining of the water through various types of materials to remove much of the remaining suspended particles), as well as chemical disinfection.

Chlorination is usually performed at several stages of the water treatment process. Pre chlorination may be performed in the initial stages to combat algae and other aquatic life that could interfere with treatment equipment and subsequent stages in the process. The major chlorination stage, however, occurs as the final treatment step after the completion of the other major cleaning processes, where the concentration and residual content of the chlorine can be closely monitored. In this phase, the chemical is more active, and less contact time is required to properly disinfect the water supply.

Chlorination can deactivate microorganisms by a variety of mechanisms, such as damage to cell membranes, inhibition of specific enzymes, destruction of nucleic acids, and mechanisms. The effectiveness of the chlorination process depends upon a variety of factors, including chlorine concentration and contact time, water temperature, pH value, and level of turbidity.

Chlorination is the cheapest, most effective way to disinfect water that is stored, processed and distributed to homes and businesses at a municipal level.   It is a cheap, efficient killer that helps protect us all from deadly microbial diseases.

When chlorine is exposed to organic contaminants, certain disinfection byproducts (DBP’s) are formed. For example, naturally occurring fulvic and humic acids in water will react with chlorine to form a toxic soup containing numerous compounds such as trihalomethanes, halocatic acids, trichloroacetic acid, and others. Chlorine will also react with the biofilm of heterotrophic bacteria so common in piping systems and many water treatment devices. Over 600 disinfection byproducts have been identified in drinking water treated by chlorine or chloramine.

Epidemiological studies have related exposure to chlorine disinfection byproducts with birth defects, pregnancy complications, certain cancers like bladder, rectal and kidney (recent studies suggest there might even be a causal relationship between chlorine byproducts and breast cancer), respiratory stress, eye irritation, skin damage, headaches and fatigue.

Traditionally, the risk of chlorine and disinfection byproducts has been downplayed, since the risk of non-chlorination is significantly greater. In fact the World Health Organization (WHO) recently stated – “the risk of death from pathogens is at least 100 to 1000 times greater than the risk of cancer from disinfection by-products (DBPs) {and} the risk of illness from pathogens is at least 10,000 to 1 million times greater than the risk of cancer from DBPs” Essentially, the consumer is being told that they  must  choose between illness and/or death from disease and microorganisms, or a steady decline in quality of life from the permanent damage caused by chlorine and its byproducts of disinfection.

Thankfully, modern water improvement technology allows the consumer a third choice:- Disinfect, and protect the water with industrial chemicals  like chlorine until it reaches the home, and then remove the chlorine and disinfection byproducts before exposing ourselves to it through showering, bathing and drinking. This is analogous to nature’s super-food – the lowly banana…I learned the hard way as a youngster growing up in Africa that the banana peel keeps its delicate fruit safe until ready to eat, and even though the monkeys in our neighborhood ate banana peels, they were definitely not fit for human consumption! I had to remove the protective skin before trying to eat the fruit.

As a water treatment professional, your primary responsibility is to provide your clients with the very best water at a reasonable price in an environmentally responsible manner.

You have many options available to protect your client and their entire home from chlorine and its dangerous disinfection byproducts. The simplest option is a replaceable carbon cartridge, but it has a major downside – restricted flow and pressure. Most professionals should rather consider a whole-house (POE) system that meets the consumers’ budget and performance requirements. I always recommend the inclusion of bacteriostatic components in carbon filters and encourage the use of an automatic disinfection injection apparatus to ensure that the carbon absorption/adsorption media doesn’t become a haven for bacteria.

Regardless of the system that you install for your client, always be sure to properly disinfect it after installation with a non-chlorine disinfectant and replace the carbon and other media on a regular maintenance schedule as recommended by the media and/or equipment manufacturer.

Always be sure to use dechlorination equipment that is manufactured to comply with NSF standards.

DEFINITIONS

Trihalomethanes – Chemical Compounds where three of the four hydrogen atoms of methane are replaced by halogen atoms. Many trihalomethanes are used in industry and the home as solvents or refrigerants. THM’s are generally considered environmental pollutants and many are actually carcinogenic. The USEPA currently limits THM’s (chloroform, bromoform, bromodichloromethane, and dibromochloromethane) to 80 ppb in treated water,

Haloacetic Acids – Carboxylic acids where a halogen atom replaces a hydrogen atom in acetic acid. Haloacetic acids in varying forms are common disinfection byproducts of chlorination.

Chloroform – A trihalomethane reagent/solvent, considered an environmental hazard. Chlorofrm is often inadvertently synthesized during the water treatment process when chlorine and related compounds are added to water. The US Department of Health and Human Resources National Toxicology Program’s eleventh report on carcinogens implicates chloroform as a human carcinogen; a designation equivalent to International Agency for Research on Cancer class 2A. It has been most readily associated with hepatocellular cancer.  Chloroform once appeared as an ingredient in toothpastes, cough syrups, ointments, and other pharmaceuticals, and was banned in the USA as a consumer product ingredient in 1976.