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Waste and Resource Recovery (Circular Water Economy)
XPRIZE
Posts: 193 admin
Zero-waste systems, capturing wastewater resources to generate value and protect the environment.
19
Comments
Everything is important and probably possible to include in the competition.
This is one of those in my opinion.
I'm also hesitant to endorse putting too much stuff that sounds good or is trendy or is part of someone's portfolio or something in one headline.
Circular Water Economy? As a criterion? I need someone to explain how that would work to me. I suspect this might mean different things to different people.
Could this be rephrased perhaps as 'Minimise resource waste/waste products that are not captured'? Or 'Efficiency of waste recovery or something? Already those are two different things.
It's also not trivial to define 'waste' and 'resource' in the given scope.
I'll try to unpack the title a little, but yes, ultimately, this is the beginning of a discussion as we currently work to refine what the criterion entails. The title is trying to reflect waste as a resource. With that in mind, the general theme is Zero Waste, and there are two key aspects - no release of materials that are harmful to the environment, animals, and humans, and resource recovery (in support of a circular water economy).
What and how around resource recovery is a question we currently explore, so your suggestions came right in time.
To share some of our thoughts and we would love to hear yours: we are exploring to encourage maximizing/optimizing resource extraction from wastewater) and/or measuring generated value and/or products towards cost recovery -- but given the wider innovation space around the added-value chain, is this something that should fall within the scope of the competition?
Perhaps you could elaborate on some of the ideas you've shared?
* re 'Minimize resources that are not captured' - do you have information about the current general challenges in this space?
* re 'Efficiency,' do you mean energy in particular? we will be tackling the systems' energy, but is there a need to seek improvements in this space in particular?
Thank you for your insights!
(Sorry if the below is obvious to everyone)
I mean it's not much of an insight, really, but anytime you remove suspended solids from water you are going to have a solid waste stream.
In the context of water in the usual context the closer you get to the start of treatment the less control you will have about what wiil be in that solid stream. Many of the things we do to remove other stuff (colloidal particles, dissolved matter) ends up 'creating' more solids to be removed. Sometime we add stuff to make this easier -- which adds more solids.
So you've got a solid stream and a liquid (water) stream to track, right?
The western wastewater paradigm is to get useable solids -- not so much because we want to recover the resource (though this is true, and changing), but because landfilling stuff is expensive and difficult and nobody wants it. So if we have stuff in the solids that people want (and, very importantly and hard to achieve -- nothing they don't want) then we have a product.
The typical application is land application for nutrients.
Wastewater is loaded with nutrients. So let's talk about removal/recovery of those. You've got the peak phosphorus people out there that are convinced we are going to run out because we've been mining it for industrial agriculture at a crazy rate for a short time and it's going to be hard to recover. Even without the recovery argument for years before that it's been a pain in the neck because it precipitates on pipes. It's not free though and not especially easy when do you start/stop recovering it? Do you want it all? At what cost to other efficiencies?
Typically N goes to N2 and is release to air so is not 'recovered' -- is that a waste or should we be considering the gas stream too? We're pumping O2/air in so that's a resource we are consuming and probably one that needs to be part of the efficiency conversation at least. Pumping too (probably 'energy'). Temperature too (possibly 'energy'). Space too (embodied energy?).
If I design a granulated sludge process where I try and make sure I'm getting N and P in solid form -- how do I design rules to compare that to the typical case of gas release of N?
Sequencing of treatment operations matters in a big way as to removal efficiencies and operating conditions and where stuff is added/removed, etc. Bardenpho isn't new but it's an example.
If at any point we add anything to make removal of something easier then is that fully consumed? Usually not and it ends up in the solid stream.
Other techniques are sometimes better at hiding where the solids are going and coming, the membranes are fouling, the brine is being discharged back whether we are counting that or not.
Ok so that's our cost and waste sort of.
So recovery -- It's already hard enough just getting the simplest things which are wet nutrient rich solids to a standard we would like to use it for e.g. land application.
So some will say 'biogas' (CH4 methane and possibly some other gases in there too). Sounds good show me a design that makes sense and recovers something to the point of use efficiently. Should the point of use maybe just be the plant? But then is my incentive to e.g. use a pump that is efficient or be efficient or to use a pump and/or electricity generator that can use my waste or do I need two pumps for different conditions and how am I going to move this stuff around efficiently and safely without using more resources I wouldn't otherwise need. And I'm still going to be left with e.g. heavy metals somewhere presumably. Or do I just store the stuff until someone connects me to some grid eventually I hope?
Incineration is another one and I think there are potentially challenges with credibly measuring that too. Turns everything away from the solid stream so if you're not looking at the stack release as waste (or a point source for pollution) it looks maybe deceptively great.
I think we should avoid falling into the trap of not counting waste that goes in the air, for example.
Also to examine the statement "no release of materials that are harmful to the environment, animals, and humans" for a second too if you don't mind. It's important to understand that this is a high and unclear bar. We're going to try and kill pathogens and depending on how we do that it's going to potentially have some negative effect on the environment. Wastewater plants can smell -- that's harm of a sort. Is that what we're talking about? Are we talking about any effect or threshold effects? For individuals or for ecosystems? And for which ecosystems?! And what sort of receiving body are we talking about for the effluent release? Big river, small stream, what animal species are around or would be able to be around? Is the environment very sensitive to Phosphorus but not Nitrogen, or the other way around, or neither, etc.
Those are sort of some of the questions I think I would be asking as part of this.
Interested to hear other thoughts on this and glad to be involved!
Short version follows:
General challenges on resources:
Nutrients, organic matter ('fuel' of a sort), getting stuff of the right grade (already difficult for solids for land application)
Efficiency:
Removal efficiency vs 'cost' vs recovery efficiency for example. Not just energy. Also, don't forget the gas stream! It's not just liquid/solid, that nitrogen is going upward. That incinerator or generator or flare is potentially an atmospheric point source.