River Boyne Water Quality Management Plan - EPA

River Boyne Water Qualiv h.Iansgemmt PlanPhosphate Balance at Navan WeirTable 5.4Long term average river flow................................... _.__....................................................................................Median total - P concentration- 0.065 mgll..... .............................................................................. .-..............................................................................................................................................Estimated export load - P- 51,738 kglyear.....................................................................................................................................................................................................Catchment area to Navan Weir- 1,610 km'.................................................................................................. " ................................._...... .- ........Export load of catchment - total P................................................................ "Median ratio ortho - Pltotal - PMedian ortho - P concentrationOltho - Phosphate at 62% oftotal P- 25.24 m'ls- 32 mglm2 year........"........................................... "................................................................- 62%..............................................................................".......................................- 40 mgll.........................................................................................................................- 32,078 kglyearThe Total Phosphate export load from the Boyne at 32mg/m2&ear falls into the category ofMesotrophic soil. The most obvious source of phosphate, in &eadily available forn~, is from thevarious sewage treatment plants in the catchment. Typ&& the phosphate load is estimated at ?grams-P per capita per day. The secondary treatme&&li result in some reduction in this load,pnrticulate phosphates in particulate form removed.&-&dge. Nevertheless, treated effluent, withoutspecific chemical or biological treatment for : removal, is likely to have concentrations inthe order of 6- 1 Omgll P.An estimate of the phosphate load from~ypewater treatment to theBoyne Catchment upstream ofNavan Weir is contained in Table 5.4, e&ressed as orthophosphate. If this load is reflected fully atI-Javan Weir, it would be approxim@?y 30% of the orthophosphate load from the catchment as awhole, leaving 70% being contrib&& through general run-off.For inspection purposes only.Consent of copyright owner required for any other use.EPA Export 26-07-2013:17:27:01