"Flow electrification" occurs whenever a fluid passes along a charged surface, creating an electrokinetic "streaming current" or "streaming potential' and is known to cause non-uniform corrosion (and other) problems in non-aqueous fluids. After observing unusual corrosion failures of copper in relatively low conductivity (≈150 μS/cm) potable water, a series of laboratory studies was conducted that verified flow electrification could also develop in aqueous systems and contribute to non-uniform corrosion. Relatively high direct streaming currents along pipelines were quantified in model systems with plastic dielectrics, which accelerated corrosion on the affected pipe section by up to 0.5 μA/cm 2 (assuming uniform corrosion). Very rapid non-uniform pipe failures (i.e., full wall penetration in 7 months) occurred in a system without dielectrics simulating a potable water recirculation system. The effects of flow electrification were virtually eliminated by addition of low levels of zinc phosphate, an inhibitor used in approximate 25% of potable water distribution systems. Flow electrification was also observed in plastic pipe systems with brass connectors. "Flow electrification" is a macroscopic manifestation of electrokinetic "streaming current" or "streaming potential," which develops whenever a fluid passes across a charged liquid-surface interface. Flow electrification of pipelines has been studied extensively over the last century in the petroleum industry, where explosion hazards and pipeline corrosion damage may result when very high voltages are generated via fluid flow in metallic pipes.1-4 Prior reports of flow electrification problems are limited to cases where the involved fluids have low electrical conductivity (e.g., non-aqueous fluids). Thus, for relatively higher conductivity fluids, such as potable water, consequences of flow electrification have largely been assumed irrelevant -although, the phenomenon has been considered theoretically 5 and practically 6-10 as summarized in Table I. Over the course of a decade of research into non-uniform corrosion of copper and dealloying-related failures of brass plumbing components in potable water systems, some practical observations of field failures could not be explained by conventional interpretations. In these cases, non-uniform pitting corrosion and failures were concentrated on the first pieces or sections of metal in the flow sequence, while identical materials downstream suffered no degradation even though they were exposed to identical flows (e.g., same pipe diameter, flow velocity and flow rate). Velocities in the pipes were well-below thresholds at which copper erosion corrosion is a concern (i.e., < 1.2-1.8 m/s), and many of the systems were parts of potable water recirculating systems with a break in electrical continuity at the hot water heater. Similar observations of non-uniform corrosion concentrated on the front portion of copper pipes in a flow sequence were also made during laboratory experiments designed to replicate the failures observ...

Having completed its inaugural Water Quality Matters column series focusing on the theme "Hot Topics in Water Quality," the AWWA Water Quality and Technology Division's committees look to extend the conversation by responding to a common question: What keeps your committee members up at night?

No abstract

No abstract

Flint, Mich., is in the process of recovering from one of the most highly publicized water crises in recent memory. Distribution system optimization is a key component of the water system's restoration and long‐term viability.