Wednesday, March 9, 2016

Model-ing Citizens

At the end of this month I'll be heading off to Europe for the latest wastewater process modeling conference - wwtmod2016 - which I'm sure will be as interesting as previous seminars in the series.  It's a pretty cool gathering of process engineers and/or modelers to dig into the process models that are a big part of what I do as a poop engineer.

In thinking about the seminar, I started to reflect on the fact that there are a lot of good wastewater process simulators on the market right now, 4 of which I'll talk about in this blog.  Before I get to them though, I have to comment on the fact that there are so many simulators in what is a pretty niche market.  If I think back to spreadsheets in the 1980s' there were several on the market - Lotus 123, Excel and Quattro Pro (the last being my fave for some time), but today the market is dominated by Excel alone (OK, there are a few diehards using OpenOffice, Numbers on the Mac or Google Sheets for simple collaborative tasks).  So how come there are so many good wastewater process simulators on the market right now? I'd like to suggest a few possible reasons:
  1. Wastewater treatment is complex (and fascinating!) and so we need models to help us figure it out.
  2. Wastewater modeling has strong "champions" who have really driven the ideas and industry in a positive direction.  In another blog I might list out several of these individuals, but from my own personal experience and because he's turning 60 soon I'll just mention Imre Takacs here.  Super nice fella with a real passion for modeling, including his latest venture with SUMO.
  3. Wastewater modeling is cool.  Let's face it, producing diurnal graphs and "playing" with a virtual plant is way cool.  That's why I like it, right?


OK, so here is a list of my personal favorite simulators.  They each have their particular strengths but I resist the temptation to say which is "best" despite being asked many times.  They're all good and useful tools.  Some do some things better than others and it's always a moving target as they each add new features. There are other simulators on the market too, but my exposure to them is limited, so the fact that I've not listed them is in no way a slight on their capabilities.  So here are, in order of my exposure to them and not in order of preference, my fave four!


For me, it all started with GPS-X 2.0 running on Unix on a HP computer.  That's real modeling!  They and everyone else shifted over to Windows which was more convenient, for sure, but our models slowed considerably until recent years as a result.  I still wonder if GPS-X running on modern machine with Linux wouldn't be the way to go!

The big plus for GPS-X is the user interface. Maybe it's because I started with this simulator, but I still love the ability to use sliders for control, set up graphs and have scenarios all in one interface.  It has it's quirks you need to learn like all the simulators, but in terms of being easy to run and adjust models, it's great.


So, I find GPS-X one of the easiest simulators to run, but BioWin has deservedly won the reputation amongst design engineers for being the easiest to set up.  There are many engineer-friendly features in the model that make it the goto for many process engineers.  Another strength of the model is the biokinetic model (ASDM), which has been termed a "super model", because it carries all variables and all rate equations around all process units which makes it easier to ensure the mass balance holds.  They also pride themselves on having decent defaults for most parameters under most conditions. You should never use any model "out of the box" without knowing what you're doing but with BioWin you maybe don't have to move too far out of the box!


Here's the new kid on the block.  Having done his time with Hydromantis (producers of GPS-X) and Envirosim (BioWin folks), Imre struck out on his own to develop a whole new modeling platform from the bottom up.  It's pretty exciting to see the development.  What I've seen so far there are two main tenets guiding it's development: (1) modern user interface (pretty cool); and (2) ease of access to the biokinetic models.  The latter is the most exciting piece for me as it's allowing us to do a lot of investigations for WERF projects and other applications.  For those at WWTmod2016, you'll get to see some of this when my colleague Patrick Dunlap presents some initial modeling for one of those projects.


Lastly but only in my own chronology as it's been around for years in Europe, is SIMBA#.  This simulator is very strong for anyone wanting to look at control.  It also has some nice energy features which they're continuing to develop and refine.  I'm thinking this "old kid on the block" may start to get some traction in North America in the next year or so.

So... what's your favorite wastewater process simulator (assuming you have one), and why?

(Copyright disclaimer... all graphics on this blog were taken from the software supplier's websites.  Please check out their sites for the original graphics and further info)

Monday, January 4, 2016

Bad data versus big data (or big bad data!!)

There's currently quite a buzz about "big data" and how water utilities might dig into all the data they collect in order to be "smarter." Several of my colleagues are investigating ways to do this under the banner of Smart Integrated Infrastructure (SII) and Smart Water Analytics. Pretty cool stuff. In a couple of conversations on the topic I half-jokingly said that wastewater doesn't have big data, it has crap data!  To avoid misunderstanding, I should clarify that by "crap" I'm referring to it being bad data and not just data describing the fecal material we treat!

Over the years I've been involved with various projects and discussions on generating and handling data in wastewater treatment. A few years ago I was involved in a couple of WERF Projects focused on developing Decision Support Systems (DSS) to prevent plant upsets, along with Dr Nancy Love and Advanced Data Mining (ADMi). The folks at ADMi did some nice data analytics to pick out anomalies that might indicate toxins in the plant influent, but one of the major hurdles we ran into was distinguishing anomalies due to toxins and anomalies due to measurement problems. This reminded me of what my ex-boss and mentor, Dr John Watts, used to drill into me which is you need to focus on good primary measurements in order to have confidence in your data. Wastewater is a tough place to try to do that! As I said, a lot of our data is bad.

So, here is my brain dump on some of the keys to making big data work in wastewater, and avoiding the pitfalls of bad big data (there's a tongue-twister there somewhere...)!

5 keys to making big data work

1. Focus on data quality rather than quantity

Starting from Dr Watt's sage advice to me years ago, and written up in one of his rare papers here, no amount of fancy analytics can overcome measurement errors, whether that's noise, drift or interferences.  You need to have confident in your primary sensors and analyzers otherwise your big data analytics will be crunching numbers that are meaningless and therefore any results you'll get will be useless.  Crap data = crap analytics!

In order to gain confidence in your data, you need to do 3 things with your sensors/analyzers:
  1. Clean them - wastewater is an extremely fouling environment an not the best place to put scientific equipment.  My experience has been that everyone underestimates how quickly sensors become fouled.  Go for auto-cleaning whenever possible and avoid installing anything in raw sewage or primary effluent unless you really need the measurement (see Key #2!) as these areas are particularly prone to fouling. Mixed liquor is actually an easier place to take measurements and final effluent the easiest of all!
  2. Calibrate them - this is generally understood, though the frequency of calibration, particularly for sensors that tend to drift, is generally shorter than ideal.
  3. Validate them - this is the piece that's overlooked by most instrumentation suppliers, I think. Analytics to validate the measurements, particularly during calibration is an area that needs much more attention.
Much of the work that Dr Watts did at Minworth Systems was focused on automating these 3 things and I've seen very few instruments come close to what he did 20 years ago!

2. Measure what matters most

I could probably make this blog an ode to John Watts and fill it with his anecdotes.  One of my favorites was one where a customer asked him to install a dissolved oxygen (DO) probe in an anoxic zone. He suggested it would be cheaper to install a wooden probe and write 0 mg/L on a fake display!  Maybe that's a little harsh, but the point is that we should only measure things that are useful to help us to run the plant and that we're actually going to use to make some decision. Generally we're lacking many important and basic measurements in our treatment plants (e.g. dissolved oxygen in the aerated 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 start measuring stuff that's interesting but not useful. You can spend some 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 instrument neglected.  It's much better to have a handful of good instruments, positioned in locations where you're actually measuring something you can control, then there's motivation to keep those sensors running well (see Key#1!)

3. Think dynamics, not steady state

A lot of the design and operational guidance in text books and training materials have 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 (worse-still, grab samples!).  All this means that we're used to thinking and talking about average daily conditions.

Graphic showing difference between composite
 sample and continuous measurement
(Courtesy Dr. Leiv Rieger/WEF,
taken from WEF Modeling 101 Webcast)
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 a dynamic system. This was first brought home to me when I was working on a plant in the UK doing biological phosphorus removal back in the late 1990's. We had an online phosphate analyzer taking measurements at the end of the aeration basin just prior to the clarifiers and we would see daily phosphate peaks of 1 or 2 mg/L every afternoon for just an hour or so, but the effluent composite sample measurements would be pretty consistently below 0.2 mg/L. To understand our wastewater treatment systems we need to measure their dynamics and then analyze that good data (having adhered to Keys #1 and #2, of course!!)  

4. 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)
  • Seasonal shifts
For each of these, the data analytics needs are quite different and need to be thought through properly. For diurnal variations, it's useful to compare one day to the next by maybe overlaying the dynamic data; for weekly trends we can do something similar over a 7-day horizon; for seasonal shifts we need to plot out long-term trends and compare them to temperature and maybe rainfall shifts.

5. Consider how to handle outliers and extraordinary events

This blog is getting long, so I'll try to wrap up this 5th key quickly!  In data analytics it's common practice to identify and eliminate outliers, assuming they're either "bad" measurements or not typical and therefore we can ignore them.  However, thinking back to my involvement in the WERF projects on DSS, a lot of what is done at 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.  This means we need to identify these "outliers" but rather than throw them away, we need to decide how to respond. Maybe this is a topic for another blog?!!

Wednesday, September 16, 2015

A Blog on Vlogs!

A colleague and I are thinking of doing a video blog on poop engineering. For those in the know the technical term is a "vlog." Now you know!  So, in preparation for setting up a vlog, I thought I should check out the competition and see what's out there already!  Here is a sample of my favourites...


In terms of water/wastewater news and professional interviews, Angela Godwin at Water World does a great job.  She goes to the major conferences like WEFTEC and ACE in addition to doing a regular video segment for their website.  In fact here are a couple of interviews of a couple of my colleagues:
My boss, Cindy Wallis-Lage, being interviewed at the recent ACE conference this year...

James Barnard being interviewed about the beginnings of BNR...

Water Sifu

OK this is a water vlog, not poop treatment, but I love this for Ty Whitman's style and it is worth watching for the theme music alone!  Very cool.  Here's a vlog on breakpoint chlorination (hey, that's relevant for wastewater treatment!)

The Rural Community Assistance Partnership

This You Tube channel has a bunch of useful educational-type videos on various aspects of water and wastewater treatment (other things too, maybe???).  I'm not sure it's strictly speaking a "vlog" but I like their informal style so it's close enough! Here's one on energy efficiency at a poop plant...

WEF Webcasts

Hmmm, now I'm really stretching it by claiming that a webcast, webinar or webinamathingy (what is the proper name?) is some kind of vlog, but hey, WEF has some cool information in their webcasts.  OK it's not a vlog, but here is one I was involved in on modeling. oh wait, it seems you have to be a WEF member now to view it.  Ah well.  OK so here are some other WEF videos, mostly of things from the annual conference WEFTEC but there are some other interesting videos too:


OK, now I may be stretching it to say WERF has vlogs but they do have some neat videos on various topics.  I like this recent one on their LIFT program (along with WEF), focused on Mango Materials.  It feels like a vlog even if it isn't one!

So, there are some pretty neat videos out there but no a whole lot of poop-focused vlogs, per se.  So maybe there is room for the Poop Engineer to try moving pictures!

Saturday, July 25, 2015

My Journey Into Sustainability

A Personal Journey into Sustainability

A few days ago I was asked to speak at a local APWA luncheon on the topic of Envision. I usually do pretty technical talks but on this occasion I thought I'd try something different and make it a little more personal by describing my own journey into sustainability as a lead-in to giving an update on Envision itself. The Prezi below shows the gist of the talk - so go ahead and click through it - but without my narrative it's not really informative, so I thought I'd add some notes below that map out my journey!


I did my bachelor's degree at Loughborough University of Technology (if you need help pronouncing it click here: Loughborough !). At the time I was an idealist who wanted to change the world to make it a better place.  I decided to do chemical engineering because I was good at maths, chemistry and physics, but I selected a degree with the long title of "Chemical Engineering with Environmental Protection" because I thought I would be able to somehow stop all those nasty chemical factories from hurting the environment!  As it happened, I ended up doing a year's internship with Severn Trent Water running pilot poop plants for their R&D group and so my glorious love for poop plants and wastewater engineering began!

Western Australia

Fast forward 15 years and I was by then working for Black & Veatch, based in our Kansas City office. (Actually we were stuck in the basement of our Overland Park HQ at the time, but that's another story!) Then I got the opportunity to move to Perth, Western Australia for 18 months working on their 3 largest wastewater treatment plants. It was an excellent experience all round but in particular I got to experience 3 things: wonderful espresso coffee (I know! who'd have thought?), awesome food (but generally crappy service!), and... sustainability.  The last one was taught to me by Susanne Cooper, who is a senior manager for Sustainability at SKM, the firm we teamed with on the program in Perth.  She has such a passion for sustainability that it's infectious and it really resonated with me.  I'm still very thankful for the way she opened my eyes and passed on that passion to me.

Back in the USA

When I left the US for Australia in 2006, the topic of sustainability was barely on the radar.  When I returned in 2008 it was EVERYWHERE! There was a real buzz about sustainability wherever you looked.  When Costco has Sustainability on the front of its magazine, you know it's going mainstream! So, that was the good. The not-so-good was the confusion and misinformation about what sustainability actually means. I heard a couple of examples of "greenwashing" where unscrupulous folks just tagged their project with the word "sustainable" to somehow magically make it so when in fact it was a very un-sustainable project on several counts!

So, what is a sustainable design?  Is it low energy? Is it recycling of resources? Is it neighbor-friendly design?  It can be some or all of these.  The "Triple Bottom Line" concept is a useful approach to figuring this out. Gauging how sustainable a project is can be a no brainer in many cases using common sense (e.g. reuse something instead of throwing it out or reducing waste materials), but in other cases taking a very narrow view of something you think is sustainable can actually cause environmental damage if you take a broader perspective.  Some recent articles talking about fracking actually show it may be having a positive impact on water resources, for example.  That is counter-intuitive, but shows how we need to take a broader perspective.  In one of my early blogs I talked about how LCA is a useful tool in this regard.


And so, recognizing that it's tricky to come up with a simple way to measure sustainability, the clever folks at the Institute for Sustainable Infrastructure came up with a great assessment tool called Envision.  What is Envision? Check out this factsheet. Why use Envision?  Here's my list of reasons:

  • It's a real "standard" endorsed by three major national organizations: APWA, ASCE and ACEC.
  • If everyone uses the same approach it facilitates clarity in communication.  Some requests for proposals (RFP) that I've seen for infrastructure projects have been vague on their requirements for sustainability or prescribe you use their specific approach which others may not know.  Picking a standard tool like Envision makes it easier to specify and respond to sustainability requirements in proposals.
  • It's open and transparent.  The guidelines are well written and honest.  There's also a genuine openness at ISI for feedback to make this a system that will work. The ultimate goal of ISI is truly to drive sustainability into our designs.  I give credit for this to Bill Bertera, who's doing an excellent job guiding ISI.
  • Its web-based, so it's easy to access
  • The tools are user-friendly
  • And finally, for all Apple product users... it's cool (or great!) So use it!

To wrap up my APWA talk, I gave some recent news and stats for the adoption of Envision. It's still relatively new, but I feel we're starting to build up steam. Denise Nelson at ISI kindly provided the following info:

·         We have over 3,400 credentialed users and another 1,000 enrolled.
·         We also have 54 trainers who have provide 25 in-person training workshops that trained over 400 people. There are several more scheduled. 
·         As far as projects go, we have 6 awarded projects, 11 additional projects registered for verification, and several more on path for registration. One project just completed the verification process, so any day now we’ll announce the 7th award!
·         The updates in June were big news:
-          new online training
-          revised guidance manual
-          revised exam
·         We recently posted a new fact sheet focused on public sector use of Envision. 
·         We recently started an ISI Envision monthly email newsletter
·         There were also two great magazine articles recently:  
-          Rubin, Debra.  “Envision Tool Moves Project Sustainability Beyond Buildings,” ENR (June 2015).
-          Nelson, Denise.  “Advancing Sustainable Infrastructure with Envision®,” CE News (June 2015).

There are several exciting things coming up soon:
·         more magazine articles, including one in Mexico
·         conference presentations and sessions
·         posting a revised Checklist
·         an ISI YouTube channel
·         restarting the committees
·         outreach at 5 upcoming public sector conferences

So, at the end of my presentation I can honestly say that 20 years on the idealistic young engineer from Loughborough University who wanted to change the world is more optimistic than ever that maybe we can change the world for the better and Envision is a great tool to help us do that. Will you do the same?

Friday, April 17, 2015

Leading Edge or Bleeding Edge? (Reflecting on Innovation)

Over the next few weeks I'll be working on an article focused on innovation in wastewater treatment. It really is an exciting time to be a poop engineer as there are several potentially game-changing processes and technologies emerging on the scene: anammox, granular activated sludge, primary DAF, thermal hydrolysis, struvite recovery, to name but a few. Add to this initiatives like LIFT and Isle Utilities TAGs that are pushing these new ideas to the fore. Finally there is Envision that enables us to evaluate the sustainability of these new ideas. As I said, it is an exciting time to be a poop engineer, indeed!

But that's not the focus of this blog; well not exactly. A few years ago I was involved in evaluating, piloting and designing what was then a pretty innovative process called the "integrated fixed-film activated sludge" or IFAS. At that time one of my colleagues said something that has stuck with me ever since:

"we want to be leading edge, but not bleeding edge" (I wish I could remember who said it first so I can give them credit, but I've heard several of my colleagues use it since and I overuse it!).

What is meant by that expression is reasonably self-event. We want to be using new ideas and pushing the envelope of improvement, but not just for the sake of doing new stuff. We want to be innovating but not just for the sake of innovation. Some ideas are ready for implementation but some need the kinks working out still and yet others may be cool but really don't offer tangible benefits over established technologies.

Another thought I want to bring to the discussion in this blog (hoping to make it a conversation!) is the "S-curve of technology implementation." This curve has been discussed widely of late amongst wastewater professionals and indeed I'll probably include it in my journal article. The discussion has mostly been focused on how can we accelerate technology adoption up the curve and/or help folks to jump across the "chasm of risk" between the pilot and full-scale. Getting the first installation of a technology or process idea is key in this. That's the main focus of LIFT and a noble one too. Let's go for it! Woo-hoo!

But... wait a minute. Take a breath. In our exhuberance for new technology I want to discuss another curve for just a moment. The technology hype cycle. I think it's a relatively new concept and is applicable to the drive to push new technologies to sell to consumers - think Video2000, think Bluetooth, think 3D TV, think the internet of everything (oooh, risky) - there are all sorts of technolgical ideas that are pushed out and hyped up that in the end don't amount to what was originally promised.


In our enthusiasm to advance innovation, are we in danger of just innovating for the sake of innovating? Are we pushing for bleeding edge and shifting from the S-curve to a hype curve? What do you think? I'm purposely putting this in a blog for open discussion so I can be accused of being a luddite or worse in the relatively quiet and safe setting of blogger (really, does anyone actually read my blogs?!). If we can discuss it here, then I'm hoping to bring some of those thoughts to the journal article in a less provocative way!

The last thing I want to do is stifle enthusiam for innovation, but equally I've seen a couple of ideas in wastewater treatment "oversold" in the past few years and then die on the vine. There was a sludge reduction technology called "Cannibal" that seemed promising and almost too good to be true. Turns out it was too good to be true for many applications, but still it's a good fit if the wastewater characteristics are right and the plant constraints dictate. Unfortunately the hype killed the idea for a lot of people... but, look at the hype curve, after the hype bump there's a drop and then a steady improvement in technology. I see a similar thing as a result of Cannibal. It certainly didn't live up to the hype, but now people are looking more closely at the cellulose material in wastewater and thinking about how we handle it (think toilet paper!). Some good came out of the hype as it drove further investigations and discussion. That's great for the industry, but maybe not so good for those bleeding out because of the hype.

My concern is that we may be doing similar things with other great ideas. Mainstream deammonification is a great concept, but in many instances it doesn't make sense. Granular AS is very cool, but again it probably won't fit all situations. I'm an advocate for struvite recovery, but it doesn't fit all faciities. Let's not hype these ideas, but let's evaluate where they fit best to play to their strengths...

Alternatively, maybe we do push on to the hype curve, bleed a little and then learn something for the next technological advancement?

What do you think?

Saturday, October 25, 2014

Reflecting on SIWW2014 and Nepal2014

This summer I went to my first Singapore International Water Week (SIWW for those in the know). It was an excellent experience and thought I'd reflect on what I'd seen.

If I had to sum up what SIWW is all about, I'd say it was a truly global center for water professionals to network. I've been to other international conferences that do a decent job of connecting utilities, and/or consultants; others do a great job of connecting researchers and academics; still others connect regulators and policy makers... now SIWW somehow manages to bring all of them together. That's quite an acheivement. I'm a process engineer, which means I appreciate technologies and how we apply them to solve water issues. Until recently I've not really appreciated the value of networking with diverse water experts from around the world, but more and more I understand the axiom "it's who you know, not what you know." Of course it's nice to know a bit too and by rubbing shoulders with smart international experts you get to add to your own knowledge.

Fast forward to October 2014 and I'm about to head off to the IWA Specialist Conference "Sustainable Wastewater Treatment and Resource Recovery" in Nepal. I'm intrigued to see the diversity of water professionals at this conference in comparison to SIWW. In addition to diversity across the various roles in the water industry, I'll be interested to see a greater diversity across geopolitical boundaries which will help us to see the differences and commonalities across our profession. I've only worked in already-developed nations and seen wastewater treatment through the narrow lense of technologically intensive and centralized approaches. It will be good to take a step back and out to see how different nations are tackling wastewater treatment. There's a distinct possibility that other nations, still developing their infrastructure, can by-pass some of the mistakes we've taken in the West and jump ahead to more sustainable solutions directly. That's what I'm hoping for in the discussion segments of a workshop I'm helping to lead: "Workshop D: Leapfrogging to off- the- grid biological nutrient removal (October 27, 2014)". We'll see. Should be interesting...


Friday, April 4, 2014

WWTmod2014 - The Process Design and Optimization Seminar

I'm sitting in Brussels airport the day after the last day of the latest in a series of seminars focused on process modeling under the moniker "wwtmod" for "waste-water treatment modeling." The previous 3 biannual wwtmod's were held at Mont-Sainte-Anne, just outside Quebec City in Canada, but the latest in the series - WWTmod2014 - was held in the lovely European town of Spa, Belgium. In this blog I'd like to summarise a few of the many highlights of WWTmod2014, but first I'd like to digress a little to ponder the name and the focus of this seminar series.

WWTmod2008 was first concieved to be a follow-up to a series of modeling-focused seminars called "Kolle-kolle" which I'm told were an excellent set of seminars in the 1990's to discuss wastewater treatment models, from which the IWA's "ASM" activated sludge models were developed. Process models have come a long way since the 1990's, shifting from the realm of academia to mainstream design and operations also. Any consultancy worth it's salt will use process models to develop or refine their designs. In fact, it's all but impossible to design a good nutrient removal facility doing nitrogen and phosphorus removal without the use of models. A few stalwart old-scholers might argue differently but they're a fading voice. This has meant that the WWTmod seminars, from the very start, have pulled together academia and practitioners to discuss process models and these models are now at the heart of process design. Despite the name including "mod" in the title, the seminars very quickly shifted into discussions about the mechanisms and processes that go into the models and so I'd argue that it is now the premiere seminar for process designers and those wanting optimize their waste water plant operations (maybe using models to help!) I can't think of another conference that draws together the top researchers from universities with experts from practice, the way that it's done at WWTmod. If you're a university researcher wanting to understand the challenges of practice, come to a WWTmod seminar. If you're a practitioner wanting to discover the latest tools and techniques to overcome your challenges, come to a WWTmod seminar!

So, what were the highlights of the latest, WWTmod2014? The program covered a broad range of topics in wastewater treatment, from screenings and grit to model extensions for trace organics; the latest in nitrogen reaction pathways and current thinking on phosphorus removal; primary settler and secondary settler performance; integrated modeling and LCA. At the closing session, the chairman of the scientific committee, Ingmar Nopens, had a slide with a few "Useful Quotes and Concepts", so maybe I'll focus on those:

"Wipers versus Washers" - there's nothing like the topic of bum wiping to get a partly humorous and partly serious discussion going on wastewater treatment. It's not pleasant to discuss the fate of toilet paper but there are serious considerations when it comes to understanding the biodegradability of the material when it gets to the treatment plant. If it's not biodegradable, it uses up treatment capacity and increases the mass of residuals that have to be handled. If it is biodegradable, it's a valuable source of material for biogas generation. Ultimately there wasn't a consensus on its biodegradability, but on the whole it was thought that it wasn't too degradable within the wastewater treatment plant (despite what it says on roll!)

The "Drinker-Barman Concept" - trying to be a little radical, I suggested that the Monod equation, near and dear to the hearts of all who model biological processes, may be past its sell-by date and that consideration of diffusion may be key to shifting to simpler kinetics where the "intrinsic" half-saturation coefficient can be ignored. I'm already getting too much into the details here but needless to say I had to use a nice analogy involving beer to make my point and hopefully make it more palitable!

"Communism/socialism versus capitalism in biological processes" - Dr Zhiguo Yuan discussed how the models we use assume that substrate is shared evenly amongst the different organisms that use it (like socialism shares out everything) but in fact there is competition for the substrate that is akin to biological capitalism.

"Being within the law is not always the good thing" - Dr George Ekama has produced many of the most memorable quotes at these seminars. A few years back he said (I'll get it wrong, but hopefully close enough): "The main problem is to keep the main problem the main problem" and he's also the source of the wipers quote above. His latest quote may sound revolutionary but it's really meant to highlight that some of regulations that govern treatment standards don't always result in the best overall environmental solution. In particular we discussed the focus on carbon emissions at wastewater treatment facilities and legislation pushing them to reduce energy use and carbon footprint when in fact the carbon emissions per person served by a treatment plant is peanuts - maybe less than 1% of their overall emissions - and they'd be better driving less or using less hot water.

Beyond these highlights another fun part of the conference was the use of twitter to post comments. I confess I was a twittering fool but it was fun! Check out the hashtag #wwtmod2014 to see!