Teaching the subject of wastewater treatment plant design has always excited me. I recall the textbooks by Metcalf and Eddy, Benefield and Randall, Sayed Qasim and those by S J Arceivala. Amongst these books, Metcalf and Eddy appealed because of the large number of “solved problems”. I was such a fan of this book that I engaged a summer undergrad student at IIT. He coded for me all the solved problems of Metcalf and Eddy in “VisiCalc” (Excel’s grandfather!) way back in 1986. I had kept these VisiCalc codes on a 8” floppy disk then but these floppies had little “shelf life”. We lost everything that we had built within a year. Alas!
[Metcalf Eddy’s book is now in 4th edition with nearly 1900 pages covering not just treatment but reuse. I wish I get another summer student to work with me to prepare a suit of Excel codes for all the solved problems with some smart VBA programming. Anyone interested? Let me know]
Todays designs of wastewater treatment plants are however rarely done with the classical approach as in the design books like Metcalf and Eddy. Imagine an Activated Sludge Process (ASP) design with Lawrence and McCarty equation or sizing of a trickling filter using Gallar and Gotas equation or the NRC formula!
The gap between a theoretical design and design in practice is widening. How do we “design” a lamella separator and how do we size a fluidized bed ASP with plastic media? Each vendor is now modifying the basic process, and adding new features to distinguish from others. These modified or improved processes are backed by research in laboratory and based on pilots. You see treatment unit more like a “black box” with less transparency on the mechanism than desired. “Sizing” of the unit is done using company catalogues and to convince, the vendor produces results of the pilot studies in the style “before” and “after”.
Indeed, for developing design for wastewater treatment plant, you need carefully planned laboratory experiments and conduct of pilot studies. There is no one size that fits for all. Each wastewater is different, and you need a customized approach, especially while working with industrial effluents. In the early days, conducting “treatability studies” was always the first step and consultants like Dr Deepak Kantawala and Prof S J Arceivala never ventured to prepare design without such studies. Today, who has the time or patience?
The idea of treatability studies was to scale up the experience of lab and pilots to design in reality. One of the rare and perhaps the only book of this kind was by Eckenfelder W W and Davis Ford. This book written in 1970 in Texas (not available anymore -and sadly someone “stole” my copy!) ) provides an approach to unit process design based on laboratory and pilot-plant studies. The intent of these two distinguished authors was threefold: first, to assist the design engineer in establishing laboratory and pilot plant programs necessary in formulating design criteria; second, to serve as a guide for sanitary engineering graduate courses in unit operations; and finally, to provide a training reference for practitioners in the field. I simply loved this book.
[Another book that needs a mention is by Imre Horvath of Hungary titled “Modelling in the Technology of Wastewater Treatment”. This book was written in 1984 and introduces how to use non-dimensional numbers to scale up of results of wastewater treatability studies. The book is however more mathematical and not an easy read. But do take a look]
Given the “invasion” of proprietary designs, you need to focus now more on treatment plant operations. We need to understand how to tweak operating parameters of a treatment plant (e.g. return sludge in the ASP). The idea is how to run the plant efficiently to address variability in the wastewater flow and characteristics and debottleneck some of the operational issues (e.g. foaming in aeration tanks, bulking sludge in secondary settling unit) to ensure compliance. Sometimes I feel that real learning happens in operations and that is how one should be teaching the subject of wastewater treatment plant. Professors are not effective as they seldom visit or know how to operate treatment plants!
I asked my Professor friend for his views he has been a Professor of Practice unlike others.
“Dr Modak, you are quite right” Professor said. “In fact, I am developing a course on understanding design and operation of a wastewater treatment plant”
“Please tell me more” I was quite excited.
“Well, the course will run over two weeks at a wastewater treatment plant. I would like to work on a plant where there is a good laboratory and a little conference room that can accommodate say 12 “students”.
The plant will have pretty basic units like screens, neutralization tank, primary sed unit that is chemical assist (i.e. clarifloculator), aeration tank with floating aerators, secondary sed unit followed by a pressure sand filter, activated carbon column and disinfection to allow treated water reuse. Sludge is thickened and then taken through a belt filter on sludge drying beds”
“Good choice Professor” I said
Professor lit his cigar and continued
“The course will essentially blend “some essential theory” and more practice experience in understanding the design and learn more through operations. A batch of 12 students will be divided into a team of four (three each) and each team will be “allotted” units to manage over 3 days. There will be rotation i.e. team of 3 students working on screens, equalization tank and clarifloculator will shift on 4th day to aeration tank and secondary sed unit. Each team will essentially “manage” the units assigned, do required sampling and analysis in the lab, do maintenance checks like oil in the gear box etc. and ensure compliance to “outputs” that I have prescribed (e.g. Suspended Solids and BOD in the clarifloculator overflow)”
“Great Professor” I liked this idea of allocation and rotation of teams to units and take on responsibilities.
“Dr Modak, each day will end by sharing the operational experience – challenges faced, strategies taken to resolve, what worked what didn’t and provide a feedback on the design. Do you remember Bob Hegg’s work on Composite Correction Program? I am giving a copy to each student”.
[I remembered the outstanding book of 1983 written by Bob Hegg of US EPA titled “Improving POTW Performance Using the Composite Correction Program”. Do grab a soft copy till it is on the web!
“And on the last two days, I will ask all the 12 students to take a “design challenge” for different scenarios i.e. how to upgrade the existing plant for 25% increase in hydraulic load or how to address high concentrations of Total Dissolved Solids or how to modify the design to meet stricter effluent standards? Answering these questions would blend the design and operational understanding of the students”
Wow, I was simply floored by this novel method of teaching wastewater treatment plant. Two weeks practical course could perfectly fit as a summer or winter course for students as well as young professionals.
Professor extinguished his cigar and said
“This course will benefit the “host” wastewater treatment plant as in this process not only their operators will get trained but they will receive a “free” report from us on plant upgradation strategies”
Oh Yes, I realized the importance of these important side benefits
“So, when would you announce this course Professor? And may I join?” I asked in all excitement
“Well Dr Modak, Sadly, I am unable to find a willing host. No one seems to be interested or serious to improve operations of their wastewater treatment plant to ensure compliance. Industries I have been asking say that everything is perfect (“all is well”) and they don’t need this kind of training cum advisory”
I understood that such a novel course of Professor was never going to run!
Also read for your fun my blog wastewater treatment plants that speak!
Last year my organization Environmental Management Centre LLP prepared a training manual for wastewater treatment plant operators under support of GIZ for SCGJ (Skill Council for Green Jobs), Write to me if you are interested in a copy]
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