Phosphates- Latest CEEP Newsletter

The Centre European d’Etudes des Polyphosphates (CEEP) is the major centre for the polyphosphate industry which carries out work on all aspects of phosphates especially recovery and recycling of phosphates, sewage treatment ad eutrophication. They have a very extensive research and information base available through their website. You can also add your name to their free newsletter which outlines current R&D in the area. Their latest newsletter (No.84) is now available. This edition and access to all the previous editions going back to 1990 are available at Link.

Decarbonisation at UK Wastewater Utilities

An article by Mark Kowalski and Line Poinel of WRc caught my eye today. It deals with the problem of energy use at UK treatment plants. Seventy five percent of their operational carbon dioxide emissions are coming from the use of electricity via the National Grid. The industry are committed to offsetting 20% of this by 2020 by a greater use of renewables. The article is published in the autumn edition of Water and Sewerage Journal.  Link

Dangerous gases from Septic Tanks

A number of people have emailed me concerning fumes from septic tanks.  The problem with all stored organic wastewaters that go anaerobic is that large quantities of hydrogen sulphide and methane will be produced.  These gases are much heavier than air and displace the air within the tank, so once opened, the gas will rise from the tank and form a dense layer around the manhole at ground level. Hydrogen sulphide is very dangerous and as I said earlier odourless at high (lethal) concentrations so there is always a potential problem.  The key thing here is to ensure that all septic tanks are cross vented.   Cesspools or sealed septic tanks are highly dangerous in this regard.  The most dangerous scenario is where the tank is in a hollow or the entrance is contained in a riser or in a building so that the gas can build up. Never climb into a tank which has only been partially emptied unless you are sure it has been vented with air.  Most complete treatment systems such as the Biocycle are continuously vented via the aeration system, so that such gases should not build up.  However, if you are working in this area, and some of you who emailed me are, you should always have a gas detector.  It is worth the investment.  For more information see Link and more safety information see Link.

Undergraduates at Leixlip WWTP

We were very lucky to be shown around Leixlp Wastewater Treatment Plant just before it snowed. Our thanks to Tom Sexton and Kildare County Council for making us so welcome.




Tom Sexton explains the odour control system at Leixlip



Outer casing of sludge centrifuge




Rare chance to see inside a
sludge centrifuge

 

Waste Framework Directive: Public Consultation

Ireland is in the process of bringing the EU Waste Framework Directive (2008/98/EC) into Irish law through the provision of new regulations.  The Department of Environment, Heritage and Local Government are now calling for comments and/or submissions on the draft regulations.  These must be forwarded to Gerry Byrne by 26 November, 2010 as Member States must complete the process by 12 December.  To access the draft regulations use this link.

Metal Variability in Sewage Sludge (Biosolids) to Agriculture Land

Sewage sludge (biosolids) disposed to agricultural land in Ireland need only be analysed once a year if disposed to agricultural land for plants of <100,000 PE according to the Code of Good Practice For the Use of Biosolids in Agriculture published by the Department of the Environment and Local Government in 2008. Metals in Irish sludges have decreased over the past 20 years resulting in their widespread use in agriculture with 76% of the 60,000 t DS produced each year now going to farmland. In a recent study done by Elizabeth Whitney of the Water Technology Research Group, the variability of sludge metal concentrations from 12 wastewater treatments plants was examined every two weeks for up to six months. The sludges showed wide variability as measured by the coefficient of variation (CV) over time with each plant with at least one metal where the CV was >50% over that period. Mean plant CV (and range) of the metals studied were Cr 29.5% (11-91%), Cd 48.0% (3-118%), Cu 73.4% (4-168%), Pb 26.5% (6-115%), Ni 46.5% (6-267%) and Zn 26.7% (6-100%). High CV values were generally indicative of an increasing or decreasing trend. However, on some occasions periods of high metal concentration were recorded indicating an intermittent source. The results show that significant variation in sludge metal concentrations occur over time and that in order to ensure safe disposal to agricultural land, the required certificates issued to farmers containing details of metals in the sludge should be either the actual metal concentrations in sludge applied or at least the upper (90 percentile) limit values based on recent monthly samples in order that correct and safe loading rates can be calculated.