From what I am starting to understand about this magical concept of ecological engineering is that we need to integrate what we know or can learn about natural processes and the environment into what we already have and know about ourselves. The potential significance of what “we” or humans can learn from the natural world is clear, look at birds, then planes, the connections already exist, we just need to utilise them more, for our own benefit.
By some sort of accident, I found myself looking and thinking about the most efficient and complex ecosystems. I had studied zoology as one of my Undergraduate majors, so I thought back to what impressed me in the natural world back then. I came up with wetlands, a functioning ecosystem on a very efficient level. Wetlands are some of the most productive ecosystems on the planet, it has been estimated that even though wetlands are only 5-8% of the earths land surface, they account for 20-30% of the earths soil pool for carbon.
So how to incorporate an already existing efficient ecosystem function into the great cities of the world? I figured this could be important, as it is expected that 70% of the world’s population will live in urban centres by 2025.
I read an article discussing the future of “green cities”, something I found easy to get excited about. Literal green cities; an obvious step in the right direction but this article argued a valid point:
“…giving buildings a biological hairdo does not a green city make.”
A city must focus on the integration of many systems to be truly utilising ecological principles, towards a “sustainable city”.
What are the Issues?
Let’s put some perspective on this first. The issue I thought could be addressed was the already costly system of getting potable, or safe drinking water, to where we want it but in a more ecological minded and cost effective way. Currently we are adding the cost for bringing clean water in, to the costs of then removing this water after use; we are effectively paying twice for our water usage. This is a very basic way to look at the current system in most of our cities. There are also costs associated with dealing with storm water, which can in some cases be linked directly to poor design of infrastructure, a growing concern with climate change and urban densification looming.
A clever man I came across during my research said something that stuck with me:
“…if more people take advantage of things like grey water systems and green roofs then our demand for water (and its disposal) may drop to the point that our infrastructure may no longer be completely necessary. Reservoirs, aqueducts and huge pipelines guiding water to major cities could wind up as over-built, archaic achievements of a different age”.
The Magic of Wetlands
So how do these incredible systems work and what functions are the ones we can benefit from? A simple breakdown of wetland functions can be found in the above image. Also a little definition for in the box to the right.
To find out more, or if don’t want to take my word for it, follow this link for the functions of wetlands on a local and global scale. And watch this home grown Aussie video made by the Department of Environment and Heritage, the Queensland Government.
We Can Make Wetlands
What I found interesting was the potential for wetlands for water purification. This is by no means a new idea, to use wetlands as a treatment process for our waste water.
First again some facts:
· Globally, two million tons of sewage, industrial and agricultural waste is discharged into the world’s waterways
· At least 1.8 million children under five years-old die every year from water related disease, or one every 20 seconds.
· Wastewater treatment facilities in the United States process approximately 34 billion gallons of wastewater every day.
· Only 1% of drinking water in many cities of western countries is used for actual drinking
· In Australia we use 341, 000 Litres of water each year
In Australia, we have already used man made constructed wetlands to influence hydrology, decrease erosion and provide shade and reduce light availability for algal photosynthesis on our farms. See here to find out about Queensland’s Wetland plan for improving farm water runoff quality by addressing these aspects.
Through constructed wetlands the processes for the purification for waste water are as followed:
· Phytoremediation- which is really a big word for using plants to remove contaminants in water. The plants take up the bad stuff through their roots, studies have showed that deeper root trees are also effective, as they can reach the contaminants at a deeper level. The other magic at this level is that the plants can also influence soil structure and characteristics by releasing organic substances that can alter chemical composition.
· Microbiological Mineralisation – fancy talk for the activity of bacteria to encourage mineral formation
· Filtration by gravel and gravity
A study conducted by Griffith University, Queensland, pointed out that in Australia very little of our sewage effluent is reused or recycled, that we tend to purify our water to then release it back into rivers and oceans. Our current disinfection processes with chlorine is not only expensive but also produces unnecessary by-products. The need is already there for a system that can remove pathogens whilst taking back nutrients and water from our waste water, it also has to be “environmentally sustainable, socially accepted and cost effective.”
A man I came a across a couple of times looking for information on sustainable cities was Jeff Speck, a city planner with a nice voice for these kind of things. He spoke about the use of wetlands to purify waste water and said that once the water has flowed through some of these wetland filtration systems:
“…the water is about as high-quality as potable water, but just to be safe, there is an additional mechanical filtration system that uses UV to blast out any remaining pollutants. The water can then be reused to water landscapes or sent back to households for toilets.”
Read more about Jeff and his work.
Tell Me How!?
I found a rather thorough study, published as far back as 1998 in the Netherlands, which considered the “Opportunities and Limitations” of the use of wetlands for waste water treatment. Check out my side box for the six steps to the purification process discussed in this study.
The study found that one of their constructed wetlands in Holland received sewage from a total of 800 people and could remove 99% of the bacterial pollution, 80-90% of COD and BOD (see my lovely section to the left below) but only 30-40% of the nitrogen and phosphorus necessary. The facility was used for 10 years for the treatment of a recreational facility.
See the diagrams below to get an understanding of how wetlands deal with phosphorus (right) and nitrogen (left):
Another study recently in Italy, 2005, compared the effectiveness of two methods of wetland waste water treatment systems.
1.. There is surface flow constructed wetlands, see the diagram below. All the action for these types occur in the upper layers and therefore can be a breeding ground for mosquitoes.
2. The other type is subsurface flow, the one I consider more practical due to the potential for these to not be a health hazard or unpleasant (sometimes wetlands smell, I know) for the public to be near. Of this type, there are another two types that have been studied, also shown in the diagrams below. The first diagram (on the left), the vertical flow, rely on a controlled source of energy but take 2/3 of the space of the horizontal flow, (diagram on right), which has fluid circulating horizontally naturally. Both of these, so subsurface flow in general, require on average 80% less space than the surface flow.
Show Me Where?!
An intuitive natural progression from here is to bring these efficient systems into our cities, incorporating an entire natural ecosystem into our day to day lives or at least into the fabric of the city. Turns out this also isn’t a new idea, in fact one impressive lady from Morocco caught my eye through TED talks. Watch the video, it’s only a few minutes long I promise!
Aziza Chaauni, an architect presents a wonderful plan to reinvigorate and transform the Fez river and so the Medina (the old town area, which is actually a World Heritage Site) of Fez from
This: To something like this:
Her grand plan also included the use of a constructive wetland within the Medina area, in conjunction with the river as a self-filtering system for the area; much needed as originally the river was so polluted they had to cover it with concrete and you couldn’t drink from the running fountains that used to provide people with drinking water. The process is still ongoing but in an interview in 2014, Aziza said that there has already been improvement, particularly downstream from the Medina, where there has been noticeable changes in biodiversity. Also attitudes have changed from viewing the river as a river, not a sewer; craftsmen have stopped polluting the river (watch the video for more, but this was a central issue to the problem in the first place).
Read more here if you would like to find more information about the transformation of the Fez River.
For a quick summary of my favourite case study, and perhaps the most impressive application I could find of the use of constructed wetlands, please enjoy this vlog posted on YouTube.
Once you have watched the Vlog I am sure you will want to see an actual clear diagram of the Flowlands project found below.
The proposed plan for the Gowanus River as explained in the video above. See here to zoom in on the image.
I have already referred to the benefits of something like this for Australia and other western countries, to decrease costs of our water treatment and to also contribute to a more ecologically minded society but I also think that the possibilities for parts of the developing world are equally advantageous.
For instance, and I only think of Mumbai as I have spent time there recently, but in India less than half of its domestic waste water is treated. If there was a way to get this constructed wetland system to be so effective as to have the end result as potable water, the possibilities are exciting! A report from the General Pollution Board in March 2015 estimated that sewage generation from urban areas is estimated at around 62,000 million litres per day (MLD) whereas the total treatment capacity available is only 23,277 MLD. Also partially or untreated sewage is the largest contributing source for the decline of surface or groundwater quality, it contributes to 70% of the pollution to streams or water bodies of India.
In Mumbai in 2016 the government was considering a new 6.39 kilometre sewage pipeline as part of a $300 million Mumbai Sewage Disposal Project. Imagine if this large amount of money went towards a design such as Flowlands that could benefit the community is so many other ways and was in line with ecological design principles. The system could be self sustaining, in that it could provide a certain area with water as well as treat the water coming out as waste. A small notch in a larger problem for somewhere like Mumbai but the benefits of these designs being space conscience is crucial for a city as dense and complex and Mumbai.
The clear benefits here of integrating ecological principles into engineering design are not only environmental but economical and, as with Aziza’s plan for the Fez, can be social too.It can also integrate an aspect of humanitarian engineering for the benefit of the people long term as well, to possibly assist in increasing peoples standard of living.