Demand for Water Harvesting Pump Systems on the Rise
By Brendan Bates, System Engineer
Global freshwater demand has tripled during the second half of the 20th century as the world population more than doubled and technological advances allowed users access to groundwater from greater depths than ever before. As global demand continues to soar, the demands on the world’s water resources are straining fresh water systems worldwide. Rivers are running dry, lakes are disappearing and aquifer water tables are dropping.
Population growth and economic development are the driving forces behind a steadily increasing demand for new water supplies. The earth’s water is comprised of 97.5 percent saltwater. The impact of this statement can be further illustrated by the following example: If the world’s water supply could fit into a bucket, only one teaspoonful would be drinkable.
In this next century, the demand for water harvesting pumping and treatment systems will increase as municipalities, homeowners, business owners, commercial and industrial building owners realize the benefit of capturing, storing, filtering and using harvested rainwater for such purposes as flushing sanitary plumbing fixtures, irrigating lawns, gardens and fields, laundry washing, vehicle washing, fire-fighting water-storage and mechanical make-up feed-water for hydronic and industrial processes.
The benefits of water harvesting systems are numerous. They reduce water bills and alleviate demand on municipal systems, but, more importantly, they reduce demand on our limited potable water supplies.
AquaHarvest Technologies, a division of Metropolitan Industries in Romeoville, Ill., are experts in the design and manufacture of pre-engineered integrated water harvesting systems. A recent project involved working with design-engineer Mark Nykowski of HP Critical Facilities Services, located in Chicago, to design a large-scale data-center in the Carolinas known as Project Dolphin.
The critical computer data-center project required the harvesting of rainwater, which is used as a pressurized source of water for flushing sanitary plumbing fixtures, as well as an emergency source of water for the data center’s critical cooling tower make-up demand.
How it works
During periods of rain, the rainwater falls on the “harvest zone.” In the case of Project Dolphin, the harvest zone is the rooftop of the facility. The rainwater is collected via the roof-drain system and eventually flows into four massive underground reservoirs. Each of the reservoirs has a gross storage capacity of 40,000 gallons, for a total gross storage capacity of 160,000 gallons.
The underground storage reservoirs were installed using an interconnecting piping arrangement. This arrangement allows each of the reservoirs to store equal amounts of water and allows all of the water to flow towards an AquaHarvest Technologies factory-prefabricated underground rainwater pressurization station.
The pressurization station is designed to collect the gravity-flow from the underground reservoirs and direct the flow of the water through two “aspiration units,” which will reduce the particulate matter in the water down to 20 microns before being pumped. The station includes two variable speed submersible pumps, each designed to pressurize the rainwater at a peak flow-rate of 80 gpm, with a target output-pressure of 80 psi and a combined peak flow of 160 gpm.
The station is designed to allow the aspiration units and pumps to be removed for maintenance, inspection and repair from grade elevation without the need to drain the reservoirs or station. This design eliminates the need for personnel to enter the confined space of the station’s wet well for regular maintenance or repair situations.
One of the station’s other unique features, which sets this design apart from other typical rainwater-harvesting system designs, is the integration of an adjoining “dry-well” chamber, adjacent to the wet well. This dry-well chamber is designed to encase the discharge piping of the station, as well as the isolation valves, silent check valves and pressure monitoring equipment. This chamber is much shallower than the wet well and is designed to allow personnel to safely enter.
Once the pressurized rainwater exits the pressurization station, the water travels below grade and enters a mechanical room inside the data center building, which houses an AquaHarvest Technologies factory-prefabricated rainwater disinfection and treatment station.
The rainwater disinfection and treatment station is a complex fabrication, which includes another unique feature designed to enhance aeration of the water in the underground storage reservoirs. It also controls and operates the pumps in the underground pressurization station, as well as performing all critical functions required to ensure the safe reuse of the harvested rainwater. The disinfection and treatment station filters, disinfects, recirculates, colorizes and stores the water under pressure, ready for its intended use.
The disinfection and treatment station includes a pre-programmed logic control center, pressure transducers, flow meter and variable frequency drives (VFDs), which operate in unison to control the flow and pressure of the water from the pressurization station. Once the rainwater enters the treatment station, the flow path first takes the water through a pair of dual-redundant cartridge filters, which further reduce the particulate matter down to the size of five microns, before allowing it to flow into the system’s ultraviolet disinfection unit (UV chamber). This additional filtering is critical to the effectiveness of the UV treatment, as larger particle sizes may tend to allow “shadowing” of other particles, thus rendering the UV treatment less effective. The use of UV is critical to the elimination of some microorganisms and cysts such as Giardia and Cryptosporidium, which originate from animal and bird feces commonly present on roof surfaces.
Upon exiting the UV chamber, a precisely-measured portion of the water flow is allowed to flow through a recirculation port, which is routed to an aeration device in a predetermined point in the arrangement of underground storage reservoirs. This measured flow is critical in ensuring that the stored water does not become anaerobic.
Next, the water is injected with a metered quantity of calcium hypochlorite. Chlorination does not kill Giardia and Cryptosporidium. Therefore, chlorination is used in addition to UV treatment. Chlorination not only provides additional disinfection beyond the UV treatment but also allows residual disinfection of the water for extended periods of time.
Finally, prior to leaving the treatment system on the way to the intended service, the filtered and disinfected water is injected with blue, food-grade dye. The dye is added to provide instant identification of secondary water and to ensure that any cross connection with fresh water supplies within the facility is avoided.
AquaHarvest Technologies is a single-source supplier of pre-engineered packaged pressurization pump stations, integrated control systems, filtering systems, purification processing, storage reservoirs and ancillary equipment for the rainwater, graywater, and secondary-water harvesting industries. Metropolitan specializes in packaging pump systems such as housed pumping stations, valve/control stations, skid-mounted water booster systems, sanitary and stormwater lift-stations, PRV stations and hydronic boiler and domestic hot water systems. All AquaHarvest and Metropolitan systems come complete with UL-listed controls and are manufactured in house.
For more information about the design and manufacture of water harvesting pump systems, contact AquaHarvest Technologies Systems Brendan Bates at 800/323-1665, ext 257 or email firstname.lastname@example.org or email@example.com.
Brendan Bates is currently a market-development manager/systems-engineer for AquaHarvest Technologies, of Romeoville, Illinois. Previously, Brendan held the position of commercial division manager for Metropolitan Industries for approximately 20 years. He has been involved in the design and manufacturing of equipment for the high-rise and commercial building marketplace for more than 36 years; over 27 of those have been with Metropolitan.
His career began at the Aurora Pump Division of the Pentair Group, where he held positions in the hydraulic test-lab, production, expediting and international-sales departments. Brendan served two terms as vice president of membership for the Chicago Chapter of the American Society of Plumbing Engineers (ASPE). He is also a member of the American Rainwater Catchment Systems Association (ARCSA), the American Society of Heating Refrigeration & Air-Conditioning Engineers (ASHRAE), and the Chief Engineers Association of Chicago (CEAC). Over the years, Brendan was able to involve two of his children and his son-in-law in the commercial building equipment business as well. Brendan and his wife Leslie reside in the western suburbs of the Chicago area.