sewers are struggling. The main problem is too much liquid, the result is raw sewage discharged to rivers and sea, or (rarely but increasingly) welling out of manholes or backing up into homes. The 2009 Pembrokeshire County Council meeting with Dwr Cymru (Welsh Water) brought up a litany of sewer failure and leaks in Newport, Dinas Cross, St Ishmaels, Solva, Broad Haven & Little Haven, Amroth, Pembroke, Llangwm, Freystrop & Hook, Milton & Carew, Burton & Rosemarket, Crundale, Saundersfoot, Lamphey, Neyland, St. Dogmaels and Haverfordwest. Another list had no spare capacity preventing homes being built. Haverfordwest was the only place being considered for SUD, Sustainable Urban Drainage, meaning diverting rainwater so that it neither enters sewers nor causes floods.
there is increasing breakdown of our most basic service. This is serious, we may not like to look at sewage, understandably, but it’s time to lift the lid.
A more serious, but less in your face problem is nutrient loss. There are now so many people consuming the earth’s mineral nutrients in food, that we cannot afford to loose them to the sea. For example the world supply of phosphorus for phosphates is limited and in few countries. We have enough for a few decades at current usage, the
is running out now. It runs out through sewers and into the sea and pollutes city waters. It is a macro nutrient, the P in
, the fertiliser behind our food behind our population levels. The feverish price spikes in phosphates which precede real scarcity have begun. Between 2007 and 2009 it quadrupled,
placed a strong export tariff, the price has subsided this year.
, however, as the capitol of rain, must keep it out of sewers if they are to work. Simon Broom, Dwr Cymru design manager, grabbed a bit of paper and drew the rise of rain water, similar to the climate curve. We were at the sewage open day in
(the event had a politer name). This astonishing increase is due, he explained, to a combination of increased hard surfaces as people tarmac their front gardens, expanding towns, roads and car parks, and to climate change. Rain is becoming more intense and violent, as well we know, and climate change is in its infancy.
The first line he drew disappeared skyward. He drew a second shaped like a mountain. This, he explained, was ground water entering sewers. Dwr Cymru’s stronger policy and new investment would slow down the disastrous increase and in ten years It would be heading downhill to arrive back at today’s level (still too high he admitted) in thirty years. Then an actual reduction could begin.
Not enough had been done in the past, Simon acknowledged, but sustainability is now the name of the game and Dwr Cymru has its engine revving, and is shovelling in enthusiasm and money to reach it’s golden shores.
“We are the only water board in the
to invest £22 million from OFWAT to get the surface water out of sewers.” He affirmed.
In a world increasingly desperate for clean water we could be saving the Welsh excess for export in pipes or in food.
Sewage contains invaluable nutrients and surface water can be a pleasure. It can water gardens, wash cars, grow vegetables, freshen air. A few years ago when I was a child we sailed toy boats in the gutter, and put on wellies to paddle in the street streams. We enjoyed rain. We have combined two valuable resources to create one pollution headache. Separating them, said, should pay for itself within 10 years in saved pumping, treatment, and infrastructure, not to mention keeping the ire of councils at bay, and reduce that dreaded sight – the lifting manhole cover.
The stop-gap solution to sewer back filling because treatment works can’t cope with the volume is the CSO or combined sewage overflow. They discharge untreated dilute sewage to the sea or river and were designed for emergency use only with a special licence from the Environment Agency. They have crept into routine use, hence the loss of blue flag status and the European dismay at our river dirt. Monitoring of discharge, one of the many tasks farmed out to private contractors by Dwr Cymru, has consequently become too expensive, so no-one knows how frequent or how polluting are the CSOs .
When the rain finally stopped last summer in
and the tourists rushed into the sea two families chatting afterwards found they had both contacted violent stomach disorders after swimming. They made investigations and were outraged at the likely cause.
I have been in meetings where town councils decide to hush the matter up, after all it isn’t proven, the tourists mustn’t be frightened off. Their health or our money, easy choice.
But there are financial impacts too. The most tragic for me is the mass die-off of cockles in the Bury inlet of the Gower. The Welsh cockle fishery was the fifth in the world to get the prized
(marine stewardship council) accreditation for sustainable fishing, and still the only one in
fully accredited. From the symptoms nutrient richness is the prime suspect, and sewerage discharged into the bay is a prime source of this. Local fishermen blame it, but the the cause of death is not certain, it could be a management issue and the Environment Agency have now been tasked to manage the fishery. The bitter wrangle has had one effect, a local Llanelli councillor wrote a letter pointing out that the CSO discharge licence contains no conditions, so it is not enforceable! This now is being changed.
None the less Dwr Cymru is acting to stop ground water entering the Llanelli and Gower sewers so the solids can be treated and used on land. Nine small diversions have been completed reducing the flow by 30 litres a second. There are 61 more to divert, and huge ingress from joint leaks, cracks and porosity in the Victorian pipework. At the same time Welsh universities are researching cockle deaths to nail the causes.
Separating ground water is the biggest challenge of our sewerage system, but it is not the most sexy. Bigger money (£70 million) is going on three Advanced Digesters for
. These massive beasts heat sewage sludge and extract methane through anaerobic digestion. The gas generates electricity, the heat by-product drives the digestion process and surplus electricity goes to the grid.
Methane comes from sewage naturally but the advanced version gets more out much faster. The residue is light and crumbly, doesn’t smell and is incredibly good fertiliser. “It will be virtually given away to farmers.” Andrew Bowen, South West waste water manager confided. “Our digester in
will be the biggest so far in
, it will be productive by December 2010, and fully commissioned in 2011..
I asked about smaller ones for our Pembrokeshire towns and was assured that the large size was efficient, although it means trucking sludge from far and wide. Three giant advanced digesters are being built in
, with a smaller one operational already near the border. I suspect that modest sized dispersed methane digestion is more sustainable in all senses, but I am not the expert! The commercial sellers of equipment are.
At home we have a series of reedbeds to treat the liquid effluent which is the bulk output of sewage. They are elegant and do not smell. They are engineered using graded stones to act as aerated surfaces for digestion, the reeds grow tall on the nutrients, a self-powered doser ensures spread of the fluids. You can live right next to this garden amenity. Dwr Cymru also uses reedbeds to treat small hamlets, I was shown round one in Eglwswrw. The engineers were particularly excited about the bird life it supported, but also showed the testing equipment at the outfall, demonstrating 90% cleansing “you could drink it, but we don’t”. It is better than UV light treatment. The only expense is annual weeding and cutting. Reedbeds as a method of treatment is limited by land availability.
Yesterday’s technological triumph of UV light treatment breaks up the
of the bacteria with ultra violet rays is being turned off in the winter to save money. Surfers who enjoy winter waves are furious. Rather than the huge expense of irradiating all the sewer output, it is better to separate and save the nutrients for the soil, ideally after digestion to capture the gas. The approach of destroy and dump is to be left on the nether shore.