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The Role of Pharmer Engineering:
The City of Meridian (City) needed to develop effluent storage and increase pumping capacity at the wastewater treatment plant in support of the new Class A Reclaimed Water Program and hired Pharmer Engineering, LLC to design the reclaimed water booster station and reservoir project. Pharmer Engineering was selected to design and build the project based on their record of providing design and engineering services for several other reclaimed water projects throughout the state of Idaho.
The scope of the project included expanding a pressure distribution main to Heroes Park in Meridian and designing and constructing a booster station, disinfection system, and two 500,000 gallon reservoirs to store the Class A water. The design of the project called for Pharmer Engineering to work with the Idaho Department of Environmental Quality (IDEQ) to confirm that the unique batch style disinfection process used to meet reuse requirements would be acceptable to the IDEQ.
The Role of Other Consultants Participating in this Project:
JC Constructors (JCC), Control Engineers, and Custom Electric (CE) were the other consultants chosen by Pharmer Engineering to implement the design of this project. JCC is a general contractor with experience in industrial and municipal water and wastewater treatment improvement projects and has worked with Pharmer Engineering on multiple design/build projects. JCC was the general contractor for this project and provided construction management services. CE is an electrical engineering firm that provided electrical designs and specifications for the reclaimed water booster station during the planning phase. During the construction phase of the project, CE was the electrical contractor responsible for installing the electrical systems for the booster station and providing the programming language to set up the automated systems within the project.
Pharmer Engineering’s Contribution to this Project:
As water usage increases, the ability to reuse water efficiently will become more important to cities and communities, especially within the western United States were available potable water is limited. To meet these increasing needs, Pharmer Engineering has been at the forefront of reuse water system design within Idaho, providing functional systems for numerous clients. This project is only the latest example of Pharmer Engineering’s continuing emphasis on sustainable engineering.
The City has been working to create a wastewater reuse program to provide irrigation water to the community. In the future, the City would like to expand this program to provide irrigation water to other properties throughout Meridian, including commercial customers such as golf courses and the cooling towers of industrials customers.
The City chose to provide Class A reclaimed water to Heroes Park as a proof of concept. Class A water receives the highest-level of treatment for reclaimed water and requires multiple redundant treatment systems, including filtration and disinfection of the water, before it meets IDEQ requirements. In addition to achieving the treatment requirements, supplying the reclaimed water to the end user is a practical concern. This project was designed to address both issues.
The project did not increase the capacity of the City’s water reclamation system, but it did provide for a more robust system and will provide storage capacity for future Class A water. Additionally, the booster station is designed to allow the City to easily expand the water reclamation system in the future. This expansion ability was a unique aspect of the project and an integral design feature. Pharmer Engineering designed easily accessible equipment and piping to accommodate future expansion of the system from 1.15 million gallons per day (mgd) to 10 mgd.
The improvements designed by Pharmer Engineering allow the City to reliably produce 1.15 mgd of Class A reclaimed water and maintain a redundant pumping capacity of 800 gallons per minute (gpm) to achieve a peak pumping capacity of 1,600 gpm. The design of the reclaimed water facility also enables the City to expand its reclaimed water program under a phased approach. Current capacities of the major components of the reclaimed water system are described below with the improvements necessary to increase the system’s capacity in the future.
The picture shown in figure 1 illustrates the current pumping configuration of the booster station.
The onsite chlorine generation system is designed to produce 100 pounds per day of chlorine (1,500 gallon of 0.8% chlorine per day). With an anticipated system dose of 7.5 milligrams per liter (mg/l) of 0.8% chlorine, the chlorine generation system’s capacity is reached at 1.5 mgd. The first phase of improvements would allow the City to produce 2.3 mgd of reclaimed water by installing an additional on-site chlorine generator and increasing the discharge piping header in the pump station from the initial 8-inch pipe to a 12-inch pipe. The reclaimed pumps would not need to be replaced but would run simultaneously. The City can add a second chlorine generation system to increase chlorine production to 200 pounds per day of chlorine, which would expand the system’s capacity to 3 mgd in the second phase of improvements.
The third phase of expansion would bring reclaimed water production to 4.75 mgd by replacing the reservoir feed pumps with larger 4,000 gpm pumps. The two 800 gpm reclaimed water pumps would remain operating, and an additional 2,000 gpm pump would be installed in the reclaimed water pump station. The chlorine generators would no longer be used since a bulk liquid sodium hypochlorite solution would provide disinfection. When the system is converted to a bulk liquid system, the City will need to upgrade the chemical metering pumps. The change to bulk chlorine will allow the City to reach the final 10 mgd design point.
In addition to expanding equipment, the mechanical piping within the system would approach engineering limits typically used for piping systems as the flow increased to 4.75 mgd. As a result, the 16-inch influent line to the reclaimed water system and the 12‑inch pipe system to feed the storage reservoirs would be increased to 24-inch pipe. The discharge piping header from the reclaimed pump station would also require upsizing from an 8‑inch to a 16‑inch pipe, and a new 16-inch magnetic flow meter would need to be installed in a vault outside of the building.
The final phase of improvements, installing a third 500,000 gallon contact/storage tank like the one pictured in figure 2, would allow the City to meet the demand of 10 mgd. The system would require replacing the two 800 gpm reclaimed water pumps with large 2,000 gpm pumps. In addition, the 16‑inch discharge piping header and flow meter previously installed would need to be increased to 24 inches and increasing the size of the 14-inch distribution line to Heroes Park would also be necessary.
In addition to addressing the technical aspects of the design, addressing the impact of the project to the engineering profession and the City of Meridian is necessary. As the public becomes more interested in sustainable design, showing that engineering professionals are addressing this need in both design and implementation will become important.
Providing the public with efficient and cost-effective examples of sustainable technologies such as water reuse will provide a foundation that reflects the efforts of engineering professionals to incorporate sustainable designs.
Using sustainable designs also illustrates to the public that waste products such as wastewater can be reused to provide a sustainable system that reduces infrastructure costs in other departments.
The City was provided with a completed booster station and reservoir system that met the original design requirements, was easily expandable, and that met all of the IDEQ requirements for a Class A reclaimed system.
Why is this Project Worthy of Special Recognition
This project provides the first example of a fully operational Class A reclaimed water facility in the state of Idaho. Class A reclaimed water is wastewater that has been highly treated to meet stringent Idaho Department of Environmental Quality water standards. The wastewater treatment facility designed by Pharmer Engineering is able to produce the highly treated reclaimed water, and the newly constructed booster station and reservoir system provide the ability to transport the Class A water offsite for use at Heroes Park in the toilets and fountain and as summer irrigation water for the soccer fields.
The booster station and reservoir system are uniquely designed to efficiently deliver water to Heroes Park. The entire system is capable of operating on the system pressure between the booster station and Heroes Park. If a small amount of Class A water is required at Heroes Park, a hydropneumatic tank is used to maintain the system pressure. If more water is required, a small pump is turned on to provide additional water. If the small pump does not provide enough flow during times of heavy use, such as during irrigation of the soccer fields, the large pumps will be activated. Having three pumping options reduces the energy requirements of the system.
In addition to the energy saving design of the system, the booster station facilities are designed to be easily expandable to increase the available pumping capacity of the system, which will enable the City to add additional reclaimed water users with minimal upgrades to the booster station. By designing the booster station to be easily expanded, the City and the community are encouraged to take advantage of the unique resource of reclaimed water.