(2/26) Editor's Note: Over the past few years we've watch local governments struggle with educating residents on the complexities of the maintenance of water and sewer systems, and the funding of upgraded. To that end, we offered the town of Thurmont two pages in each of the next three editions to help articulate answers to those questions.

Introduction to Municipal Drinking Water Systems

Have you ever wondered where the water running out of your tap comes from? Unless you have a private water well, it is supplied to your residence by a Municipal (Public) Drinking Water System (PWS). Municipalities are responsible for providing clean, safe, and reliable drinking water to homes and businesses within a community. This is accomplished by a system comprised of water sources (which can be ground water or surface water sources), treatment facilities, storage tanks, and a distribution network. Approximately 90% of the United States population receives its water from a public water system.

Typically, source water is transported through a transmission pipe or main and treated at a water treatment facility to ensure it is clean and safe to drink. Treated water, known as potable water, is then pumped to storage tanks, such as water towers, to store the treated water until it is called upon due to system demand. As soon as system demand calls for more potable water, the water is transported to your home through a network of water distribution mains. Today, water mains are comprised mainly of ductile iron or polyvinyl chloride (PVC) pipe. An interesting fact about water mains is that in the early years of community water system development, water mains were often made of actual wood. Some of these wooden water mains around our area were still in service as recently as a decade ago.

Continuing with the journey of potable water, once the water arrives at your property, it has to enter into your house from the water distribution main. This is accomplished through a "tap" on the water distribution main called a corporation stop or corp for short. Connected to the corp is what is known as the water service or also referred to as a water house connection. The water service is typically comprised of copper or plastic pipe material. Residential water connection sizes are typically ¾" or 1" in size.

In communities, a customer will typically find what is called a curb stop located at the edge of the municipal Right-of-Way. A curb stop allows for a licensed water operator to exercise the curb stop and shut water off to a property if an emergency would arise. Moving past the curb stop, a customer could notice a meter pit located in their yard. This can be easily identified by a lid that is typically 12" in diameter, depending on the application. Inside the meter pit is the residential meter that records the amount of treated water consumed by the customer. Another common location for the water meter is within the basement of the residence.

America’s drinking water is the highest quality in the world. If you have questions about your drinking water, customers can contact their local water supplier to get a Consumer Confidence Report (CCR). The CCR lists the levels of contaminants that have been detected in the water, including those identified by Environmental Protection Agency (EPA), and whether the PWS meets state and EPA drinking water standards.

Water Sources

A community water system’s sources supplying the water flowing out of your tap may be miles and miles away. Municipal water systems commonly use surface water or ground water as their source of water or a combination of both. Once the water is extracted from the source, as previously mentioned, the water is transported to a water treatment plant where it is treated before being distributed to consumers.

Surface Water

Surface water sources include lakes, rivers, or reservoirs. In Maryland, most of the population, particularly the Baltimore-Washington metropolitan area where 5 million people live, is served by surface water from the Potomac River and the Baltimore City reservoir system. Surface water is easily contaminated by human activities through pollution and runoff. Surface water is highly susceptible to sediment, litter, and debris being washed into it during storms or rain events. This reason alone is why source water protection is very important to help reduce the amount of pollutants being transported to surface waters.

Ground Water

Groundwater sources, often referred to as "Wellheads", are commonly used as a source of municipal drinking water. These wells are drilled deep into the ground to access groundwater that exists in pore spaces of rock. These porous, water-filled rock formations are called aquifers. Aquifers can be either confined or unconfined. Confined aquifers are sealed and protected from the surface, and surface water, by an impermeable layer. Unconfined aquifers are not protected by an impermeable layer and surface water can flow into the aquifer.

Due to contaminants coming from human activities at the surface, unconfined aquifers are more susceptible to contamination. The State of Maryland has a wide range of geology and aquifer types. Wells in the aquifers typically vary from high yielding ones (commonly more than 264 gallons/min) in confined and unconfined, unconsolidated sandstone layers on the eastern shore and southern Maryland to relatively low yielding ones (generally less than 79 gallons/min) in the fractured rock areas of the Piedmont, Blue Ridge, Valley and Ridge, and Appalachian Plateau provinces of central and western Maryland. Some of the fastest growing suburban areas; however, are located in the Piedmont and Blue Ridge areas, and many are supplied by wells in fractured rock aquifers or small reservoirs. (Hammond, 2018) Fractured rock aquifers, common in western Maryland, are unconfined. In this region, water seeps down through the soil, sediment and degraded rock into faults and fractures in the underlying bedrock. Water availability depends upon the size of fractures as well as the degree of interconnection between fractures.

Water from wellhead sources typically requires less treatment than water from surface water sources since it is naturally filtered by the earth. The water is pumped to the surface and then transported to a water treatment plant.

Water Treatment

Water from common sources like wells, rivers, reservoirs and lakes contain sediment, organic matter, bacteria, and other impurities that may not be safe to drink. After the water has been sourced from either a wellhead or surface water intake, it is transported to a water treatment facility. The purpose of water treatment facilities is to remove impurities and contaminants from the water. This is done through a series of processes that include coagulation, sedimentation, filtration, and disinfection. The Safe Drinking Water Act requires the EPA to establish and enforce safety standards that all public water systems must follow. (EPA)

Coagulation, Flocculation, and Sedimentation

This process involves adding chemicals called coagulants, such as aluminum sulfate or ferric chloride, to the dirty water. The chemicals cause small particles of dirt and clay to clump together by neutralizing the charges of the naturally ionized particles. Charged (ionized) particles repel each other similar to like-sides of magnets. Removing this charge allows the particles to stick together, making it easier to remove them from the water. Once the coagulant is added to the water, it is slowly mixed in a flocculation chamber. This process allows larger clumps of dirt to form, these clumps are called floc. After flocculation the water is sent to a sedimentation chamber to sit still for a period of time. This allows the heavier particles settle to the bottom of the tank creating sludge that can be disposed of in a landfill. With the sludge at the bottom of the tank, the clearer, cleaner water is removed from the top. Or if using dissolved air flotation in place of sedimentation, floc is carried to the top of the tank by a cascade of air bubbles then skimmed off, leaving clearer water behind.

Filtration

After the coagulation, flocculation, and sedimentation process, the water will look much clearer, but there will still be bacteria and very fine particles left behind. Most of these remaining impurities can be removed by filtration. Sand filtration is used to accomplish this because it very efficient. Water can be further filtered by activated carbon filters, which can be thought of as giant "Brita®" filters. Activated carbon has many tiny pores that captures microscopic impurities and is not always necessary for health reasons but improves the taste and smell of the water.

Disinfection

After the filtration process, the water will be crystal clear: however, some microorganisms like bacteria or viruses could remain, so the water is then disinfected. There are three major methods of disinfection which can be used individually or in combination with one another. These three methods are chlorine, ozone, and ultraviolet light disinfection. The most common method of disinfection in the United States is chlorine disinfection. Chlorine disinfection works by adding chloramines (chlorine bearing chemicals) such as chlorine dioxide or monochloramine to the water. These chemicals are very effective at killing any microorganisms in the water at the plant, and will also continue to kill any bacteria introduced to the chlorinated water elsewhere in the system. Ultraviolet radiation is also a widely used method. This works by shining ultraviolet light through the water which scrambles microorganisms DNA. This does not kill the existing bacteria but makes it impossible for them to multiply, and bacteria or viruses that cannot multiply are harmless. Ozone disinfection works by infusing ozone into the water which kills microorganisms as well as improves the taste and smell of the water. This process also requires the removal of leftover ozone after treatment using sodium bisulfate because ozone is not safe for human consumption. After all of these processes, the water is tested for purity before leaving the plant.

Water Distribution

Water is pumped out of the water treatment plant to the distribution system which consists of water towers, transmission and distribution water mains, and eventually your home’s plumbing.

Water Tanks and Towers

Water towers and stand pipes keep water networks pressurized. Many towers are open flowing holding tanks for pressurized water systems. There is not a pump at the base of the tower, rather the pressure from pumps at the source or treatment plant carry water up to the tower. Once water is in the tower, it is at a higher elevation than the rest of the system. This allows the system to rely on gravity to keep water flowing throughout the system. This is why, during a power outage, households on municipal water supply continue to have running water, while households relying on private wells run by electric pumps will lose water supply during an outage. Water tanks can hold and store millions of gallons. Water demand fluctuates throughout the day and the tower keeps the pressure in a network consistent without having to use great amounts of electricity running pumps. Keeping consistent water pressure in the water mains is important for water quality as well. If pressure were to drop, and there was a leak on the water system, negative pressure could allow groundwater to seep into pipes, bringing bacteria with it.

Water Mains

Water mains are the primary pipelines that transport treated water from the treatment facility to distribution networks. These pipes are typically made of materials such as cast iron, ductile iron, PVC, or steel. The diameter of the pipe depends on the amount of water that needs to be transported and the distance between the treatment facility and the distribution network. Water mains can be divided into two categories: transmission mains and distribution mains. Transmission lines are used to transport water over long distances, typically from the sources to the treatment plants, and are typically made of large-diameter pipes. Transmission lines can be above ground or underground, depending on the location and availability of space. Above ground transmission lines are typically supported by large towers or poles, while underground transmission lines are buried in trenches. Distribution mains are smaller pipes that transport water from the plant and water storage tank to the individual consumers. These water mains are often buried beneath roadways.

Pumps

Pumps are used to transport water through the distribution network. They are typically located at the treatment facility or at various points along the distribution network. Pumps can be used to increase water pressure, overcome elevation changes, and maintain a constant flow of water. The type of pump used depends on the specific needs of the system. There are several types of pumps, including centrifugal pumps, positive displacement pumps, and submersible pumps. Typically water must be pumped out of the water treatment facility into the distribution system at a minimum pressure of 40 psi so that the pipes remain pressurized even at higher elevations. Maintaining pressure is necessary to prevent external water in the ground from infiltrating the pipes through joints or cracks and contamination the system.

Hydrants

Hydrants are used for several purposes, including firefighting and maintenance of the water system. They are typically located along the distribution network and are connected to the water mains. Hydrants can supply water from 500 to 1500 gallons/minute. Water mains must be equipped to handle that capacity. Hydrants are attached to a water main by a vertical pipe called a riser. Wet barrel hydrants are used in regions that do not get very cold, where the risk of water inside the hydrant freezing is very low. In wet barrel hydrants, the hydrant is filled with water at all times and the valve to release the water is above ground. In dry barrel hydrants, used where temperatures routinely drop below freezing, the water is controlled by a valve underground below the frost line. Hydrants are not variable flow, meaning they are either completely on or completely off. The pressure of flow at any given hydrant is determined by the water pressure present at that location in the water distribution system. Often times the color of a fire hydrant can indicate its flow capacity or source.

Meters

The amount of water you use in your home is measured by a water meter. The meter measures the volume (gallons) of water passing from the distribution main to your home. The meter readings are used to accurately bill homeowners for their water usage. Meters can also be used to detect leaks in your personal plumbing.

Regulation & Emerging Contaminants

The Environmental Protection Agency, along with other government agencies, regulate the chemical composition of drinking water. They do their best to keep up with the evolving world of chemical compounds by testing water for newly discovered compounds and monitoring research on how they affect human health. These new chemicals are referred to as "emerging contaminants". Most emerging contaminants are man-made and introduced to the environment through industrial activities.

Thurmont Water System

The Town of Thurmont's water system source is ground water consisting of five wells. Wells 3, 4, 9 are in the Frederick Limestone Aquifer and are treated at the same treatment plant. Wells 7 and 8 are in the Gettysburg Shale Aquifer and each have their own separate treatment plants. All of these wells are drilled through rock containing voids and fissures as are the majority of wells in this region of Maryland. The Maryland Department of the Environment (MDE) considers these types of wells as being drilled in unconfined aquifers and susceptible to surface water intrusion.

MDE has determined through testing that Well 3 is under direct influence of surface water and it is treated as a surface water source. This means that Well 3 raw water is filtered through a Diatomaceous Earth Pressure Filter to remove any small particles, known as turbidity, that may be present. This filtering of Well 3 raw water is the first treatment process this well will undergo. The filter's effluent turbidity levels are constantly recorded by use of a turbidity analyzer and reported monthly to MDE. Other treatment processes at each plant are ion exchange softening to reduce the levels of calcium and magnesium, known as hardness, in the raw water to a MDE approved 68-85 milligrams per liter.

Wells 7 and 8 treatment plants also have aeration treatment that allow for the release, by off gassing, of any volatile organic chemicals that may be present. The final treatment process at all these treatment plants is disinfection which is the injection of a sodium hypochlorite solution to kill any bacteria that may be present. After the addition of sodium hypochlorite, the water flows into underground tanks called contact chambers. These tanks vary in size at each plant depending on the amount of water flow and time needed for the disinfectant to kill any bacteria.

The goal of the Plant Operator is to inject enough disinfectant to kill bacteria in the raw water and have a residual disinfectant remaining to kill any bacteria the water may come into contact with once it leaves the treatment plant. Pumps, known as service pumps, then move what is now "finished water" from these contact chambers to the distribution systems network of water mains leaving the treatment plant.

Each individual well is metered for gallons per minute and total gallons pumped and recorded daily. MDE has established the maximum amount of water each well is permitted to withdraw in a day. These individual well withdraw amounts are reported to MDE twice annually. The finished water leaving the treatment plant is also metered and recorded daily for gallons per minute and total amounts pumped. These daily amounts that are pumped into the system are reported to MDE monthly.

Once the finished water leaves the treatment plants, it flows through a network of various sized underground piping known as the distribution system. These water mains are typically buried 3-4 feet and generally follow the layout of the streets throughout town. Smaller piping, or service lines, are connected to these water mains and run to each individual household and commercial building.

In most cases at the edge of the public right of way, a water meter is installed in the service line. The water meter measures the amount of water that passes through it and are read quarterly by Town Staff. Customers' water and sewer usages are billed from the readings. Once the service line leaves the meter, it becomes the responsibility of the property owner to maintain. After the service line enters a building, a main shut off valve should be present followed by a pressure reducing valve in all newer homes or when replacement of existing plumbing in older homes is done or as needed. Pressure reducing valves are used to regulate the water pressure inside of buildings typically between 60 and 70 psi. The pressure in the water mains often exceed this recommended household operating pressure.

Water mains in Thurmont’s system are pressurized by the three elevated and one covered in-ground storage tanks. These water storage tanks not only pressure the system but also provide water storage to be used during peak use periods and to fight fires. Thurmont has two distinct pressure zones due to differences in elevation within the Town. Two of the tanks hold water at a higher elevation to maintain pressure in elevated areas of Town, while two hold water at a lower elevation to provide pressure to lower areas. These two pressure zones are isolated from each other using valves in the water mains. Water can be moved from the lower pressure zone to the higher pressure zone when needed by a pumping station located between the two zones. The water levels in the storage tanks are what controls the operation of the wells at the treatment plants. When the water level in the tank drops to a pre-set level it signals the wells to run. The wells then will supply water to the system that is needed and pumps the excess into the tanks to refill them. When the tanks fill to a pre-set level, the wells are turned off and any water needed is then supplied by gravity throughout the system until the cycle repeats itself.

Public water systems are all similar in some aspects but each are distinct in how they operate and the treatment processes required. Thurmont’s current water system is the result of over 100 years of growth and change. Population increase, technology, and ever changing water quality standards have impacted how the system has evolved and will continue to do so in the future.