Saturday 31 March 2012

Living island solutions

The challenge
To capture and remove plastic and other solid wastes from rivers. Any solution must be ecologically benign, or even add something to the river environment.

 Figure 1: A willow tree smothered in plastic wastes after winter flooding.


Figure 2: Detail of plastic waste caught up on a willow branch. This provided the initial concept.

The (living) solution
 A floating boom made out of living materials such as willow and alder branches, reed mats etc. woven into mats and extended along a linear boom, that is placed in the river to capture floating and submerged wastes during winter flood events. The design is such that the boom closes into a circular island as it fills with waste. This is then drawn toward land by its own weight where it remains as the floods recede. Buoyancy is currently achieved using disposable plastic bottles found along the river bank.

Figure 3: The very first prototype made of woven alder and willow. It's now become a duck's nest.

Figure 4: The first island using a floating platform. Branches are placed thorugh the platform in bundles.

Initial tests carried out by dragging the boom behind a boat have shown that the system is capable of effectively collecting floating waste. More research is required into alternative designs and testing is required under differing flow conditions.

The benefits
  • The materials are all locally available and biodegradable, being the waste product of coppicing/pollarding of willow and alder in the early spring;
  • Jobs are created using mostly free materials;
  • A living boom/island provides a habitat for wildlife as it grows during summer months;
  • It is visually appealing;
  • Living biomass also serves to improve water quality by absorbing nutrient loads;
  • Collection using barges is cheap and easy;
  • Disposal by incineration provides a feedstock for local combined heat and power (CHP) plants;
  • Education and research into re-naturalisation are promoted.
More photos are available here 

Update 2nd April:


I built another, similar system using alder and willow branches in bundles placed through a large wooden pallet, which I found washed up on the river bank (see figure 2 above). The system became  submerged at the front when I towed it across the lake and the semi-submerged branches caught some items while bottles passed through the branches on the topside and were washed onto the pallet. It seemed to work okay (video to be uploded!) and is now tied up under a willow tree on the big lake. I hope that birds will use it as a nesting platform.

When I returned to the harbour I noticed that a pair of ducks were already making a nest on my prototype floating island! 

 Figure 5: A coot adds a small branch to the floating island prototype, showing the natural habitat that this produces.

The advantage of providing habitats is seen by their preference of floating natural material to the stern ladders of boats! The mess they create drives boateres mad, so this solution should be promoted in harbours for example.

We do need to experiment with different designs in terms of ease of construction, durability, growth potential, cost etc. Bundled branches are easy to fix and could be employed both horizontally in booms and vertically as with the island.

Update: Mentioned project on Guardian article about water and green growth.

Friday 23 March 2012

The Thames Tunnel - an open debate


This is an open thread about issues surrounding the controversial Thames Tunnel proposal by Thames Water (link to TW FAQs).

To kick off an overview: The river Thames is increasingly suffering from pulses of raw sewage entering into the river after heavy rainfall. The problem is mainly due to the fact the combined sewerage system (CSO), which carries both foul sewege and rainwater run-off has become overloaded due to a combination of population growth, reduced surface permiability and the increasing effects of a changing climate, namely droughts and flooding.

The TT has been proposed as solution to this problem and it is hoped will avoid excessive fines being incurred due to breaching European directives on pollution (the UWWTD). These issues need to be clarified as the proposed completion of the TT would currently be around 2023, and substantial fines may still be possible until succesful completion.

Another issue relates to the cost of the proposal currently estimated at over four billion pounds. There is a possibility that the proposal entails excessive costs and may therefore not be an acceptable solution under the UWWTD.

Cheaper and possible more afffective alternatives to the TT may still be favourable in the light of this. These include SUDS, water saving schemes, and other measures right down to end of pipe approaches such as supplying oxygen to river water in so-called blubblers.

Finally the framework that resulted in the privatisation of the water industry is something that cannot be ignored. Is the supply and treatment of water not so fundamental that it should be state owned and run?

I look forward to your thoughts.

BTW. A useful website on the legal aspects of the TT relating to infrastructure can be found here thanks to Angus Walker.

BTW.

The water industry is an interesting example of what happens with privatisation. Decades of under-investment left the water and sewerage systems in a desperate state. The government of the day pleaded poverty and simply sold off the assets to private hands who stripped the best assests (mostly land, which was used for buildling houses in the housing boom) and made a tidy profit. They never solved the problem of providing enough water and sewerage treatment and here's the evidence:

The Thames regularly suffers from pulses of raw sewerage while this year a hose pipe ban is being imposed in the South East. And all this over twenty three years after privatisation in 1989. Thames Water reckons that by 2020 the thames will suffer a constant flow of raw sewage unless customers fork out a fortune to pay for the now 4.1 billion pound Thames Tunnel. Such are the wonders of private investment that they insist the tunnel is of national strategic importance and so should be partly paid for by the nation. The last time I checked, the Thames flows through London and not right through Britain.

So much for privatisation. Thames Water is now owned by an Australian investment banking group, Macquire after having been sold off by the German energy corporation RWE, also one of Europe's most polluting businesses.