I tend to go back and forth in my view of just how different industrial wastewater treatment is from municipal treatment. I used to be fixed in thinking there were many significant, complex differences but now I often find myself thinking the differences are not that great. Just recently though, somewhat contradictory, I realized that succesful lab testing in the industrial evironment can be a bit trickier than lab testing in municipal wastewater treatment plants. Let's begin with the simplest case, considering how chloride can interfere with measuring the chemical oxygen demand (COD) in a was ..read more

It's a scary time of the year! You should be afraid, very afraid. So stay safe my friend and look for what's behind you. Do your best to be inside well before dark. Check that your doors and windows are locked and your curtains are closed, because you know neither who is out and about nor what mischief is afoot. Don't be tempted to peek through the blinds, trust me, you don't want to know who is looking back at you from the other side of the window. Don't let them know you know they are there. If you ignore them, they will leave you alone. Everywhere I go I see gravestones popping up on front ..read more

For the last several years I have been doing a lot of field testing to determine the potential for struvite scale to form in anaerobic digesters and dewatering equipment (primarily centrifuges). In this post I will be focusing on struvite scale that forms in centrifuge centrate lines, with the "centrate" or "filtrate" line from dewatering equipment being one of the most common locations where struvite forms in wastewater plants with anaerobic digestion. For the wastewater treatment plant operator, if you have a struvite problem developing you typically won't know until it is too late. That's b ..read more

Turbidity is defined as the degree to which light is scattered by particles suspended in a liquid. The measured turbidity depends on the wavelength of light and the angle at which the detector is positioned. In this post I want to explain the different turbidity units of measure: NTU, FNU, FTU, FAU, and JTU. Each one of these turbidity units are based on calibrations using the same formazin primary standards. Therefore, when a formazin standard is measured, the value for each of these units will be the same, however the value on samples may differ significantly. NTU: Nephelometric Turbidity Un ..read more

Bacteria are amazingly complex, even though each is comprised of only a single cell. Bacteria make up about 95 percent of all the microorganisms in activated sludge. As long as enough nutrients are available, bacteria can multiply (cell generation time) very rapidly by splitting into two identical cells. Some can divide in two in only 11 minutes. Many can double in 20 to 30 minutes (Glymph, 2005). Glymph, Toni. "Wastewater Microbiology: A Handbook for Operators." Denver, Colorado: American Water Works Association, 2005. The rate at which bacteria reproduce in an activated sludge system is some ..read more

It can be helpful to quickly estimate solids production in wastewater. Certainly, each wastewater treatment plant and its collection system, with variable ratios of domestic, commercial, and industrial flow contributions, is going to be unique regarding its specific wastewater characterization. But for those situations where you don’t have plant operating data you can use more general estimates to begin an analysis. The information provided below is quoted from an excellent, highly recommended, textbook called “Wastewater Sludge Processing” written by Izrail S. Turovskiy and P.K. Mathai. This ..read more

Introduction Hydrogen peroxide can be used to increase the dissolved oxygen (DO) concentration in an aerobic bioreactor, often referred to as “DO supplementation.” Using peroxide is rarely a first choice because chemically increasing DO is more expensive than using a mechanical method (diffused aeration, mechanical mixing, etc.). But if you are in a situation where, for example, you have aeration blowers out-of-service due to equipment failure and the DO has dropped below 2.0 mg/L, impacting nitrification and/or BOD/COD removal, hydrogen peroxide can be used to restore bioreactor oxygen levels ..read more

Introduction Many wastewater plants suffer capacity loss due to inflow and infiltration. For the majority of municipal treatment plants there is likely to be a seasonal impact resulting from rain events, snowmelt, spring thaw, etc. But there are also wastewater plants located next to or near the ocean that suffer from infiltration every day due to seawater intrusion. The impact of high influent sulfate concentrations from seawater intrusion on anaerobic digestion will be the focus of this post. Specifics of the particular plant are shown in the simple block diagram below. Definitions In any di ..read more

This post provides tips and insights I've come across focused on chemistry topics for wastewater treatment operators. A search on Google for “Rule of Thumb” leads to the following definition: “A broadly accurate guide or principle, based on experience or practice rather than theory.” PPM vs. mg/L I was reading a chapter in a "wonderfully-friendly" textbook for water and wastewater treatment plant operators, from the chapter titled Chemistry 7: Chemical Dosage Problems and realized I have been too relaxed in often using the units of meassure ppm (parts per million "parts") and mg/L (milligrams ..read more

GSA, MCRT, SRT, and Sludge Age Defined I think there is confusion, sometimes, in how operators (which includes me) define the terms mean cell residence time (MCRT), solids retention time (SRT), sludge age, and, though seldom used these days (was it ever used?), Gould sludge age (GSA). In this post I want to have a detailed discussion about MCRT and SRT, leaving sludge age as a phrase that can be used to describe either of these two parameters equally well or as you may prefer. Often, and I have been guilty of this myself, mean cell residence time, solids retention time, and sludge age are use ..read more