Sewage Spillage in Jersey

I've just been listening to BBC Radio Jersey where a spokesman for Transport and Technical Services was explaining to the presenter that in very wet conditions, they have to let raw sewage seep into the bay, because even the cavern (a large storage area rather like a capacity) cannot cope with the overload.

There were several things not said, however....

I clearly remember an earlier explanation being given a few years ago, which I suspect is the right one, that the capacity of the pumping system from the West of the Island is not fast enough to take the increase in volume in raining weather. It functions in that respect rather like the road network, which has several feeder roads from Western and North-Western parishes all coming together into one road at Beaumont. I suspect the lack of capacity in flow is the real problem with the sewage system, and why it has either to be sent out to sea in such cases, or blow covers and go into Goose Green marsh.

The other matter, which is obvious, is that rain water runoff and the sewage network are combined. Extreme wet weather does not cause humans (as far as I am aware) to suddenly increase their use of the toilet, shower, bath etc - the culprit is the rainwater, and the fact that the system does not split the two. The more rainwater is set off on its own system, and discharged to sea, the less of a problem there would be. In the 1970s, there were inspections of properties in St Brelade to ascertain that this was the case, and presumably to try and rectify it. I don't know what happened to that survey and its aftermath, but nothing much seems to have been done. Perhaps we need a code, like that which is in force in Ohio (1)

1101.2 Where required. All roofs, paved areas, yards, courts and courtyards in buildings shall drain into a separate storm sewer system, or a combined sewer system, or to an approved place of disposal..

1101.3 Prohibited drainage. Storm water shall not be drained into sewers intended for sewage only.


But perhaps there are concerns that storm runoff may contain unacceptable levels of pollutants (from roads etc)? There are, and have been, modern ways of dealing with this that reduce the impact of storm rainwater's load on the system. There is a very good paper from 2003, called "EUROPEAN APPROACHES AGAINST DIFFUSE WATER POLLUTION CAUSED BY URBAN DRAINAGE" (2)  which deals with this, among other matters:

Storm water management

Storm water management concepts are combining unsealing of paved areas, infiltration of runoff from disconnected areas, storm water re-use, distributed retention, delayed transport and treatment (the latter to be described in the following subsection). The pressure to rethink conventional drainage systems and realise such modern concepts is due to mainly water quantity problems (insufficient hydraulic capacity of sewer systems as well as of streams and rivers) but also quality requirements. In the sense of sustainable development, ecological criteria are taken into account in these drainage concepts which are potentially much closer to nature than the traditional approach has been. The decentralised solutions (e.g. infiltration structures as main element) are used as best management practices (BMP) and are recently named 'sustainable
urban drainage system' (SUDS). Practical planning experience shows the necessity to involve drainage planners into town and traffic planning at an early stage because boundary conditions are fixed then which are very important for feasibility and efficiency of the local storm water management concept.

SUDS are a very popular topic in urban drainage in Germany. Beginning with first exemplary projects in the late 1980s which already include investigations of impacts on groundwater quality SUDS are now widely used in drainage planning. The approach is also beginning to be used more extensively in other European countries, e.g. in the UK, France and Switzerland as well as in the US and in Australia.

The first mentioned two elements of SUDS (unsealing and infiltration) as source control measures have a reduction effect on the runoff volume, the others an attenuation effect on the peak flows. Both effects are reducing the hydraulic stress for the receiving waters (disturbance of benthic fauna). Infiltration closes the natural water cycle by increasing the ground water feeding. Böhm et al. (1999) stated an efficient decrease of emissions of hazardous substances into receiving waters (especially heavy metals, nutrients only to a minor extent), but partly these loads are transferred to soils and wastes. Therefore measures at source are necessary in parallel (see sub-section 'Replacement of hazardous substances'). Additionally it is expected that the elimination efficiency of the existing treatment structures improves by 10-15 % in terms of pollutant load emissions due to the reduced inflow rates.

Links
(1) http://codes.ohio.gov/oac/4101:3-11
(2) http://www.ucd.ie/dipcon/docs/theme04/theme04_05.PDF

Limits to Growth: Sewage in Jersey

When I was a youngster, Jersey had a Sewage Board Committee, which later changed its name (and some of its functions) and became the more euphemistic Public Works, and then Public Services, and now TTS.

All the recent talk about the incinerator has meant attention has been diverted from the Medical Officer of Health's recent report, which actually is giving us some facts and figures about sewage, which are rather worrying.

Liquid waste disposal

The sewage treatment plant at Bellozanne is ageing and has been in operation since 1959. Over the years, treatment processes have been updated as the population has grown and as more stringent effluent standards have been required. The plant was initially built to deal with a lower total volume of liquid waste than it does today. It currently receives on average 33,000 cubic metres per day - a 36% increase since 1977.

This increase has occurred despite the many surface water separation schemes undertaken during that time which should have reduced flows. The mains drainage systems work well in general, although in extended periods of inclement weather, the network becomes overburdened with surface water from combined drainage systems (where foul and surface waters are mixed together) and from ingress through leaking pipe work. The cavern under Fort Regent is designed to take up the excess from the town area and, when flows in the system return to normal, to pump back collected sewage into the works.

The report recommends:

the early formulation of an Islandwide liquid waste strategy to determine the appropriate level of improvement and extension to the mains drainage network, along with an appropriately sized and located replacement for the Bellozanne sewage treatment plant

What is missing from the report, and perhaps may become available from TTS, is the capacity of the sewage treatment plant in tons per day, and how close it is to reaching that capacity, and how much plant is needed per head of population to sustain that capacity.

This is what I call "real joined up thinking", and there seems to be precious little of it around. Population growth always looks at housing, roads, sometimes schools, but never at the distant end of the infrastructure needed to support it. Until, as with the incinerator, it has to be done hurriedly out of necessity, because when firefighting, it is the wrong time to stop and assess the merits of different engines.

In the University of London Study "Determining Sustainable Development Density using the Urban Carrying Capacity Assessment", the authors note that "The determination of the capacity of a system is fairly straightforward when managing suburban facilities as water supply, sewage treatment, and transportation."

There is also an energy cost to sewage treatment. The UK Parliamentary Office of Science and Technology, has produced a paper on "Energy and Sewage" in which they note:

Over 10 billion litres of sewage are produced every day in England and Wales. It takes approximately 6.34 gigawatt hours of energy to treat this volume of sewage, almost 1% of the average daily electricity consumption of England and Wales. The actual energy used will depend on the quality of sewage and intensity of treatment required. Typically, there are three stages of treatment:
. Primary. Solids are physically settled out.
. Secondary. Bacteria convert organic matter to a carbon-rich sludge.
. Tertiary. Further treatment may be used to remove more organic matter and/or disinfect the water.

Effluent is discharged to fresh, ground or coastal water.

Sludge is applied to agricultural land (62%), incinerated (19%), used for land reclamation (11%) or used for other purposes, such as composting or landfill (8%)

It would be interesting to note the statistics regarding Jersey's use of sludge.

The report also notes that:

There are mature, widely-practised technologies for generating fuels from sewage treatment and research has
identified future methods for exploiting sewage as an energy resource . In 2005 - 2006, the amount of
renewable energy generated on water industry sites was 493 gigawatt hours - 6.4% of the total energy used to
treat water and wastewater.

Regarding sustainable energy, it is also worth noting that biogas can be generated from the system, and this can offset against the energy consumption. Whether this would be viable in Jersey is another matter, considering the small size of the Island, but it is worth considering.

Biogas production from sewage sludge treatment, via a process called anaerobic digestion, is already a well established means of generating energy in the UK. Bacteria use organic matter in sludge to produce a mixture of methane (60 - 65%), CO2 (35 - 40%) and trace gases. Impurities, such as hydrogen sulphide and water, are removed and the resulting biogas is then commonly used in boilers or combined heat and power (CHP) systems. For example, anaerobic digestion facilities are being developed at United Utilities' Davyhulme sewage treatment plant that will provide 90% of the site's power via CHP. Biogas may also be used for other applications, such as vehicle fuel, if CO2 is also removed. In Linköping in Sweden, trains, buses,
taxis and some private cars run on biogas.


Links:
Report on Energy and Sewage
http://www.alphagalileo.org/images/pdf.pdf

Determining Sustainable Development Density using the Urban Carrying Capacity Assessment
http://eprints.ucl.ac.uk/208/1/paper78.pdf.

Medical Officer of Health report
http://www.gov.je/Health/public_health/OurIslandOurHealth2008.htm