Waste water treatment control standards

Hey all,

Question regarding waste water treatment control standards. Without too much context, i am wondering if waste water for some reason doesn't use ethernet to control VFD's and hardwires direct. In all other new work/upgrades i have done it has been ethernet controlling the drives. Getting some pushback on wanting to do this. Anyone have experience in this field, and can comment on the industry standard of wiring in a Hand/off/auto control station Whether that is PLC or hardwired. Thanks.

One reason to not use ethernet or other comms for VFD control is for the case of replacement VFD. If a VFD needs to be replaced at 4pm on a Friday, and the only thing available is a different manufacturer/model than what is there, the chances are that it will be able to work with 4-20MA for speed demand and a relay contact closure for run/stop.

First off there is no industry standard on instrumentation and control. Individual engineering firm and owner preference vary and dictate design.

Second, the industry is very risk-averse. That's understandable since screwing up can cost millions of dollars and people's lives.

Third, there are many facilities that use serial and ethernet communications for control - I've designed some. It is becoming more common, along with telemetry and the Industrial Internet of Things implementation. However manual overrides and hardwiring critical devices like E-Stops is still good practice. Most often Ethernet is employed to link the local PLCs together and to SCADA systems. The distributed architecture eliminates a single point of failure and improves reliability.

I do many wastewater projects. Other opinions may vary, but I find them very old-school.

Many panels still require 30mm push buttons and relay logic (most of the time only controlling 2 motors or so)

In all of my startups at a wastewater treatment facility (which isn't as many as others I'm sure) I almost never interact with a 'controls' guy; instead it is usually an operator or maintenance man. My guess is that they are the ones replacing it and aren't tech savy enough to download new parameters/etc.

I'm doing several WW projects right now that will all be Ethernet controlled. In one case the EE insisted on removing all of the control devices from the front of the VFDs and after they were installed and we were commissioning them, Maintenance insisted on adding them back in "just in case". But when the integrator went to implement the local control functionality into the overall scheme in the DCS, they discovered that if anyone actually put one of the VFDs into Local control, they could get the entire system really screwed up and have serious problems with mandatory reporting functions. So the functionality was change to be called "Off Line Test Mode" that requires prior approval to be implemented. Bottom line, some more advanced WW control and reporting systems are in some cases becoming too complex for manual overrides and analog control anyway.

I work exclusively with water and wastewater authorities. The level of knowledge differs massively from one to another. Some still use standards that are 30 years old simply because they don't know better. Others have no standards, and just let whoever turns up do whatever they want.

The aversion to using modern control techniques could be due to either of the above, or others that people have listed.

I used to avoid using anything other than hardwired controls for our smaller rural clients. But given how easily we can change a Schneider ATV6xx drive now that is set up properly with FDR, I find we're more likely to avoid having to send a technician down. I can talk the local tech through setting up the drive name and then restart it... back online. Not that we've had to do many at all.

I think maybe if you can show them how easily they can change a drive you might win them over.

We do however still always provide manual controls via hardwire. But that operation mode is clearly defined as only for emergency operation.