Instead of water flowing out of fire hydrants and running to waste, the Zero Discharge Flushing (ZDF) process utilizes a trailer-mounted pumping, filtering, and re-chlorinating system that circulates the water within the water distribution system. The ZDF unit is connected with large hoses between two fire hydrants, which creates a temporary “loop” in the water distribution system. A pump on the unit circulates water at prescribed velocities, and it is passed through a series of filters that remove intentionally “stirred up” sediment and particulate matter. Disinfectant can be added to further improve water quality and ensure its safety, something other methods cannot achieve. Inline turbidity meters indicate when desired clarity levels are met, taking the guesswork out of knowing when the flushing has achieved its purpose. The result is improved water quality, increased disinfectant residuals, conservation of two vital natural resources — water and the energy it took to pump and produce it — all at a lower cost without taking the value of the saved water into account! Since very little water is lost with the ZDF Process, NPDES issues are eliminated. Additionally, the flushing can be done by a crew of two to three operators and typically doesn’t require that any sections of the distribution system be valved off.
The standard process has a maximum system pressure rating of 200 psi max. We also offer the capability of 270 psi.
Our patented flushing system can remove settled particulates, biofilm, iron, and manganese and some sources of color. The ZDF unit, as well as conventional flushing methods, may not remove heavily encrusted “barnacle” types of long-term rust buildup found inside old cast-iron and steel mains. The fix for these issues may require other extensive, expensive and very intrusive solutions.
Once the ZDF system starts circulating the water and stirring up any sediment, the water quality quickly decreases to a brown rusty color with turbidities well over 100 NTUs. Typically, within two to five minutes, water quality returns to accepted distribution-system standards. Each water distribution system is different, and conditions could be much better or much worse.
The savings realized when using the ZDF system will vary depending on a variety of factors. These factors include how flushing is currently being performed (conventional or uni-directional), number of operators being used, wholesale water costs and water production and delivery costs. Utilities can reduce these costs by 50% or more. However, the greatest benefit may come in the form of your customer’s positive perception of your utility by leading by example in water conservation; and no longer opening fire hydrants and wasting tremendous amounts of water. This is especially true for those utilities that have voluntary or mandatory rationing requirements in place, which typically include fines for wasting even the smallest amounts of water.
Yes, the ZDF system and unit can meet these AWWA recommended flushing velocities in 2-inch to 12-inch water mains. With ZDF, water hammer potentials are eliminated, as the water velocity is being provided by the ZDF unit’s pump, not the rest of your distribution system: Only the water within the temporary piping loop is being circulated, filtered, and disinfected. This greatly minimizes the impact on your distribution system and the customers who rely on it. If the flushing of water mains larger than 12 inches is desired, two ZDF units can be hooked up in parallel.
Yes, however, this is something that only the utility can determine is desired, safe, and appropriate given the system’s age, type of pipe, etc.
Yes, each ZDF system comes with a chlorinator for injecting very small concentrations of chlorine for boosting residuals.
After working extensively with technical experts, we’ve developed our process in a way that enables the ZDF system to combat issues by both flushing and boosting chloramine levels. This is achieved by precisely adding the appropriate amounts of chlorine during the flushing cycle, which then combines with the measured free ammonia in the water to reform chloramines.
Many utilities flush solely to remove water with high free ammonia levels, in an effort to prevent nitrification from occurring. The ZDF unit can be used solely for that purpose as well, reducing the free ammonia levels by reforming chloramine levels to the desired concentration in large sections of main (much larger than a flushing cycle).
The significance of using our ZDF unit is that it can target specific areas where and when chlorine/chloramine boosting is needed, which is a feature unique to our product. Used in this manner, it functions as a portable re-disinfection boosting system. Flushing is also performed at the same time, which will significantly slow down the deterioration of the system’s disinfectant residual in the future.
Yes, every component that comes in contact with distribution system water is NSF 61 Certified and approved for use in potable drinking-water systems.
The ZDF system has two separate stainless-steel filter housings. Both are ASME “U” stamped and compliant. The first filter housing is designed as a roughing filter utilizing 12 disposable filter bags that remove particulates down to 1.0 micron in size. Though the run times on these filters are dependent on the amount of particulate matter, biofilm, etc., in the distribution system being flushed, we estimate typical run times will be in the one-to-three-week range. Again, depending on the condition of your distribution system, run times could be longer or shorter. The filter vessels have a flow capability in excess of 2,000 GPM. We have found that using the 1.0-micron filter bags is the most cost-effective way to filter out particulates, but there are other bags and cartridges that filter at different sizes that will fit the filter vessels that allow for a variety of scenarios.
Included with the ZDF unit are two sets of hose ramps that allow traffic to pass over the hose under such circumstances.
Yes, the ZDF unit has a built-in flow meter with a remote read display that enables you to attain exact flow information, and a totalizer for tracking use.
Turbidity meters are located at the pump inlet and at the outlet of the polishing filter to determine water clarity (start to finish).
Yes, it can be used as a portable booster and transfer pump. The ZDF System also adds the increased benefit of being able to filter and disinfect the water being pumped — something traditional booster systems cannot do.
Yes, GAC backwashing is an additional function the ZDF unit can perform. Simply connect one end of the transfer hose to the backwash drain outlet of the GAC filter and the other to the inlet of the ZDF unit. A second transfer hose is connected from the discharge of the ZDF unit to a hydrant located in the distribution system. The backwash cycle can be controlled by the ZDF unit without interruption, and the cartridges/bags can be disposed when backwashing is complete.
Yes. To do so, one end of the transfer hose is connected to the drain outlet of the tank and the other to the inlet of the ZDF unit. A separate transfer hose is then connected from the discharge of the ZDF unit to a hydrant. Again, the benefits are that the ZDF unit will filter the water that is being transferred into the distribution system and can also be chlorinated if desired.
Yes. Instead of discharging water into the street, a 2 1/2-inch hose is attached to the discharge side of the test meter, with the other end being connected to the inlet side of the ZDF unit. This water is then filtered — and disinfected if desired — before being returned back into the distribution system via a hydrant. The ZDF unit’s flow meter can be used to confirm the accuracy of the meter being tested.
No. Once the ZDF unit is connected to the hydrants or blowoffs, and is pressurized by opening the hydrants or blowoffs (full open); the ZDF unit becomes a temporary part of the distribution system, just as a booster-pump system does when used to transfer water or boost pressures. The distribution system water does not leave the distribution system; it is circulated through the connected “temporary loop” created by the ZDF system. The water is not pumped anywhere (out or back in), it is only moved in a circle (circulated).
Most hydrants are of the dry- barrel type; dry-barrel type hydrants must be fully opened while flushing, otherwise the drain hole located at the bottom of the bury (which only seals when the valve is in the full open position) will allow water to escape. During extended operations, if the hydrant valve is in any other position water will flow out of the drain hole with enough force to erode and undermine the area around the hydrant bury. As a result, when using conventional or uni-directional flushing methods, operators are likely turning hydrants to the “full open” position and may not be monitoring or controlling the flows to keep them within or reaching desired flows. The ZDF unit enables you to precisely adjust the rate of flow with our variable speed pump and flow meter. An attached placard shows the operator exactly what flow rate is needed to achieve the desired 5 ft/sec velocity for each size main to be flushed. This removes any chance of missing the target velocity, and addresses issues such as water hammer or lining damage.
Possibly. This could be accomplished if the water from the hydrant was discharged into a water tanker truck while performing the flow test and then was withdrawn by the ZDF unit and pumped it back into the distribution system. This has not been tested yet, but the concept is simple and ZDF will be evaluating this task in the near future, as it provides for another opportunity to conserve water.
No, the ZDF system was designed to be connected so that the direction of flow inside the main being flushed is in the opposite direction of flow of the distribution system. As an example, if the general distribution flow is 30 GPM traveling through a 6-inch main being flushed, the ZDF unit will circulate the water to its desired flow rate of 441 GPM in the opposite direction. The 30 GPM distribution system flow will be circulated through the ZDF system and then continue on down the water main in its normal flow.
As the ZDF system circulates the water between the two hydrants in the opposite direction of the distribution flow, any stirred-up sediment will be carried to the inlet of the ZDF unit (along with the 30 GPM distribution flow). All this water is filtered and then circulated back into the main where the 30 GPM distribution flow will continue down the main under normal flow conditions.
No, if the distribution flow is 300 gpm in that 6-inch main, there’s no reason to flush that section of main. It’s being flushed all the time.
Yes, biofilm has been a big problem with almost all water systems, and up to now the only way to remove biofilm was to conduct extensive flushing to waste. With the ZDF system, you can not only remove this issue, but you can stay on top of biofilm buildup through a dedicated year-round program using the ZDF system. Because there is very little water wasted, the ZDF system can be employed 24/7/365 with no adverse effects towards your distribution system or customers.
Yes, this issue is a big concern with water providers. Not only have you just seen large amounts of good, treated drinking water spill down the gutters during a water main break, but once repairs are complete, your crews are now going to flush the area to ensure that the water is safe and clean. With ZDF, you could flush the area of concern and add disinfectant without wasting more water. Now, the water is clean and safe, and it’s also ready for Bac-T sampling.