Water Online

MAR 2017

Water Innovations gives Water and Wastewater Engineers and end-users a venue to find project solutions and source valuable product information. We aim to educate the engineering and operations community on important issues and trends.

Issue link: https://wateronline.epubxp.com/i/795216

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Page 22 of 34

Measure only what's useful to you. What will you actually use to best manage the plant? Some treatment plants lack important and basic measurements (e.g., DO in the aeration basins, airflow to each aeration zone, and electricity use by blowers), but we need to be careful in our enthusiasm not to swing to the other extreme and take measurements that are not especially useful. You can spend serious money measuring ammonia and nitrate all over a treatment plant, but unless you're actually using it for control, the measurements will eventually be ignored and the instruments neglected. It's best to have a handful of good instruments, positioned in locations where you're actually measuring something you can control, and to try to keep those sensors running well. Think dynamics, not steady state. A lot of the design and operational guidance in textbooks and training materials has simple equations into which you plug a single number to get your answer (e.g., sludge age calculation or removal efficiency). Similarly, influent and effluent samples are usually flow-weighted or time-averaged composites. We're used to thinking and talking about average daily conditions. However, the reality is that our treatment plants see significant daily variations in flows and concentrations, and therefore we need to look at them as dynamic systems. For example, an online phosphate analyzer taking measurements at the end of the aeration basin just prior to the clarifiers might reveal daily phosphate peaks of 1 or 2 mg/L every afternoon for just an hour or so, but the effluent composite sample measurements could be consistently below 0.2 mg/L. To understand our treatment systems, we need to measure and analyze their dynamics. Recognize different timescales. Hand in hand with dynamics is the need to think about different timescales: diurnal (daily) variations, weekly trends (especially weekend versus weekday differences), and seasonal shifts. For each of these, the data analytics needs are quite different and need to be carefully considered. For diurnal variations it can be useful to compare one day to the next by overlaying the dynamic data. For weekly trends we can do something similar over a seven- day horizon. And for seasonal shifts it is often beneficial to plot and compare long-term trends to temperature and maybe rainfall shifts. Consider how to handle outliers and extraordinary events. In data analytics it's common practice to identify and eliminate outliers, assuming they're either bad measurements or not typical and therefore something to ignore. But experience shows that a lot of what is done at water and wastewater treatment plants is trying to keep the process stable in response to abnormal events, such as upsets from shock loads or toxins, or, more typically, responding to wet weather for wastewater plants or major line breaks or droughts for water treatment. We need to identify outliers, but rather than throw them away, we need to decide how to respond. In a nutshell, Big Data is about taking all the data we now have at our fingertips and turning it into knowledge that we can apply to operate our treatment facilities better. The right data, analytics, and decision framework can drive water (and energy) utilities to optimal performance. n 20 wateronline.com n Water Innovations DATAMANAGEMENT Andy Shaw, Ph.D., is a global practice and technology leader with Black & Veatch. He is responsible for wastewater treatment and sustainability and has special expertise in instrumentation and computer modeling. He is also a keen user of internet-based knowl- edge transfer, including his blog http://poopengineer.blogspot. com/. Shaw has led or served on multiple WEF committees and was featured in a WEFTEC 2016 Water Online radio interview about Big Data. About The Author Modern instruments are more reliable than they were in the past, but they still need to be cleaned and taken care of. Tools such as Black & Veatch's ASSET360 system help water utility managers follow in the footsteps of their energy utility colleagues to harness data for improved decisions and operations. In terms of accuracy, the instrumentation that we have now is better than ever, whereas sensors were a weak point in the past.

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