Over the years, modelers have developed a range of methods for taking limited demand data and developing well-calibrated models. For example, OpenFlows WaterGEMS’s Load Builder has 12 different methods for loading demands based primarily on the source of data.
Read Tom Walski’s blog to learn about inner, outer, and nominal pipe diameter and the differences these pipe diameters have in your hydraulic modeling. Various types of concrete pipe are the exception to this table in that such pipe is essentially designer pipe where the pressure class depends much more on the prestressing wire rather than the thickness of the concrete, which is really there to prevent the pipe from being crushed. For such pipe, the nominal diameter is close to the ID.
Disinfectants like chlorine and chloramines work by oxidizing chemicals and microbes in the water, and that’s why we use them. The problem is that by doing their job, their concentration decreases, and it’s possible to end up with low or zero levels of disinfectant residuals. You can’t continuously monitor residuals everywhere in your system. Your OpenFlows WaterGEMS and OpenFlows WaterCAD models can help you determine residual disinfectant levels throughout the system, identify problems and develop approaches to maintain residuals such as changing dosing, switching disinfectants, adding booster stations, flushing, and blowoffs, …
NPSHr is a property of the pump and is a function of the flow. This value is determined by testing done by the manufacturer and is usually presented as one of the pump characteristic curves. You want to ensure that the available NPSH (NPSHa) is greater than the required NPSH (NPSHr), or the water will vaporize in the pump and damage the pump.
Picking the right number of pumps and which ones to run at any time without wasting energy is tricky. The problem gets especially tricky when you have the potential to mix constant and variable speed pumps, and there is no storage in the system, so you can’t simply run pumps efficiently and turn them off when a tank is full.
Pumping energy is usually one of the largest components of operating costs for most water systems. And it’s not a trivial cost for wastewater utilities either.
Water and wastewater do a very good job preparing for what I’ll call “routine emergencies”—pipe breaks, short-term power outages, sewer blockages, pump mechanical failures, etc. There are standard operating procedures and frequent drills in well-run operations to make sure we can deal with such conditions. But what about the big emergencies? The ones that never happen until they do. We’ve had a taste of this with Covid, and the folks in Texas received an even stronger dose during last winter’s big freeze.
There is no shortage of conferences serving the water industry. Each of them contributes something to our profession, and attending is usually worthwhile, if not life-changing. But which ones should you attend? You can’t attend all of them, or you wouldn’t get any work done. I’ll run through a few of the conferences I’ve attended, and I’ll give you my thoughts below.
A key input to a water distribution system model is the demand assigned to locations in the system. For most of the history of modeling and most models today, these demands are based on a known volumetric flow rate. Some, however, would argue that all water leaves the system through some kind of pressurized orifice and demands should be modeled as pressure-dependent. Software today, like OpenFlows WaterGEMS, has the ability to model demands as volume-based or pressure-dependent.
A key input to any model with pumps is some form of pump head curve showing flow vs. pump head. Given the curve, the model can tell the user the exact point on the pump curve at which the pump will operate.