AIE 16
Standards for several parameters are set under Condition 2.3 of your discharge licence W 294/94R1. The results show non-compliances with the conditions of your licence.
Glan Agua have taken the time to review this for Kylemore quite thoroughly with the attached being their output which suggests Ferric can be used and should result in a vast improvement in the levels of Phosphorous being measured from the outlet of the system. The proposal to also redirect existing septic tanks to the system also being beneficial.
The NIS is actually viewable on the planning file 11/1003. I don’t believe we actually carried out an AA as would be done now but the NIS was assessed and the council was satisfied with it’s contents.
Review of Kylemore Abbey Wastewater Treatment Plant Report
Glan Agua
The current Emission Limit Values (ELVs) are as follows;
• Biological Oxygen Demand (BOD): 5mg/l
• Chemical Oxygen Demand (COD): 25mg/l
• Total Suspended Solids (TSS): 10mg/l
• Fats, Oils and Greases (FOG): 5mg/l
• Total Phosphorous (TP): 2mg/l
• Orthophosphate (OrthoP): 1mg/l
• Ammonia: 0.2mg/l
• Nitrate: 10mg/l
• pH: 6-9 pH units
The current treatment process consists in the following:
• Multiple septic tanks on the network
• Inlet pump station (directly to primary settlement)
• 2no. precast primary settlement tanks (36,000 L ea.) directly upstream of the RBCs operating in series at the main plant.
• RBC
• Final Settlement Tank (FST)
• Sludge Return
• Phosphorous Reduction
• Polishing Lagoons (Reed Beds)
Whilst the current treatment process capacity cannot be accurately evaluated without additional information, it is fairly unlikely to be able to comply with the extremely stringent ELVs currently in place for the following reasons:
• There are numerous septic tanks on the network, which could lead to excessive retention time, septicity issues and ultimately detrimental impact on the process performances. Rationalisation of the network should be considered so that the remaining septic tanks operate within typical design parameters. This can be seen from the particularly low concentrations of solids and low BOD/TSS ratio in the influent, as well as anecdotal evidence (smell in the 2no. precast septic tanks).
• The storm water network looks to be amalgamated with the sewer network allowing introduction of high volumes of rain/storm water into the treatment system.
• BOD/COD/TSS ELVs
o The BOD/COD/TSS ELVs are extremely stringent. Typical ELVs for an RBC treatment process based on the current influent sample results would be 25mg/l BOD, 125mg/L COD and 35mg/l TSS.
• OrthoP, TP and residual aluminium ELVs
o For the OrthoP and TP ELVs, a chemical removal stage would be required to guarantee the ELVs. Based on the jar tests carried out which have shown the ELVs are readily achievable using chemical phosphorus removal, the system was designed assuming a Fe mole ratio of 3.5mol Fe/mol P. Assuming 29.9d storage, this would mean a coagulant storage tank of around 1000l would be required. 2no. chemical dosing pumps of 10l/h each (based on the estimated peak wastewater flow of 52.7m3/d plus 50% safety factor, i.e., daily peak flow of 79.1m3/d and assumed peak flow of 9.9m3/h) would be required.
o Optimisation of the chemical mole ratio through regular sampling and adjustment of the pumps will allow the process to minimise the risk of residual metal carryover. This would be further strengthened if a tertiary filtration stage was also provided as suggested above based on the BOD/COD/TSS ELVs. An iron probe could be provided; however, it should be noted that the licence does not include for an iron limit either.
o Due to the scale of the plant, and to the high costs associated with an OrthoP online monitor, the provision of this equipment to control the chemical dosing pumps would not be considered as viable.
• Ammonia and TN
o The existing RBCs is unlikely to be able to comply with the extremely stringent current ammonia ELV. With RBCs, the oxygen used for the nitrification reaction is only provided through diffusion from the ambient air to the wastewater when the disc is above the water, and it is therefore difficult to guarantee full nitrification. Available effluent results provided to Glan Agua for 2021 showed that the effluent from the RBCs was nonetheless generally compliant with the ammonia limit.
o For the nitrate ELV, a denitrification zone with nitrate recirculation (so that nitrates generated in the aerobic zone can be returned where BOD availability is greater) would be required – the existing process does not have such a zone and the existing ELV therefore cannot be guaranteed. An anoxic zone would need to be provided to guarantee compliance with the ELV.
o It should be noted that, due to alkalinity consumption by nitrification and coagulant dosing, alkalinity boosting using NaOH may be required depending on the outcome of the stormwater separation process and operational results when resuming ferric sulphate dosing.
▪ Assuming no denitrification, the max. storage volume required for 27.2d storage would be around 2000l, and 2no. 9.2l/h chemical dosing pumps would be required.
▪ If there was an anoxic zone provided upstream of the aeration stage with internal recirculation of nitrates, the denitrification reaction would allow for some alkalinity recovery and drop the requirement to 1500l (29.3d storage) storage and 6.4l/h chemical dosing.
o Finally, it should be noted that the existing polishing lagoons can actually have a detrimental impact on the effluent quality, due to the risk of algae or other organic matter growing in the lagoons, decomposition of vegetation, animal contamination etc. This was not seen for “Kylemore Remote WQ Baseline Data- 01.11.2021” apart from the 19/10/21 sample where the COD concentration at the outlet of the RBC (SW7) was 29mg/l, against 47mg/l at the outlet of the lagoon.
However, it is a risk that should be considered if a larger upgrade of the WwTP besides the provision of chemical dosing was considered
No application form would have been submitted for the review. An application form is only submitted if it’s an application for a new licence. The council issued a notice of review and the licencee submits info based on this. The info submitted by the licencee is what makes up most of volume 2. The NIS is actually viewable on the planning file
11/1003. I don’t believe we actually carried out an AA as would be done now but the NIS was assessed and the council was satisfied with it’s contents.