East Cambridgeshire District Council Water Cycle Study Detailed ...
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East Cambridgeshire District Council Water Cycle Study Detailed ...

East Cambridgeshire District Council Water Cycle Study Detailed ... East Cambridgeshire District Council Water Cycle Study Detailed ...

eastcambs.gov.uk
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20.03.2013 Views

WwTW Consent parameter Stage 2 Water Cycle Study: Final Report Sept 2011 Current consent standards P - Upgrade Requirements Discussion Consent limits required for no deterioration No change required 34 Process assessment - Upgrade required? No Cambridgeshire Horizons East Cambridgeshire – Detailed WCS Is there space to expand WwTW It is considered that the consent changes required at the WwTWs in Haddenham, Witcham, witchford and Little Downham are relatively small and hence are likely to be achievable without the need to add new process streams to the WwTW. There should be no (or limited) phasing implications for growth in these catchments. Process upgrades required at Soham (for BOD), and Littleport WwTW (BOD and P) are significant, and hence would require new process streams to be added in order to meet the tighter quality conditions on the new discharge consent; Littleport would also require the addition of P-stripping. It is considered that upgrades required to deliver these improvements as part of the new application for a discharge consent would not be delivered in full until AMP6 (2015 onwards). Because both WwTWs are considered to be at their volumetric discharge consent before a new consent would be needed, the maximum per annum connections to each of the WwTWs would need to be limited in agreement with AWS. It is possible that upgrade works could start in the current AMP5 round (2010 to 2015) to allow a larger number of connections; however, on a precautionary basis, growth has been assigned a red category until AMP6 (1015 onwards) with growth across the rest of the plan period assigned an amber code for wastewater treatment to reflect that upgrades need to be completed first. Flood Risk Constraints In order to determine whether the increase in wastewater discharged from the WwTWs as a result of growth is likely to impact on flood risk downstream, estimates were made of the percentage increase in flood flows that would occur for a variety of return period events. The Flood Estimation Handbook (FEH) was used to derive flow estimates of the receiving watercourses of Buwell WwTW (Burwell Lode), Soham WwTW (Soham Lode) and Bottisham WwTW (Swaffham Bulbeck Lode) for a range of flood return periods (full results are provided in Appendix 5). The calculated additional flow potentially discharging to the receiving watercourses is: • Burwell WwTW – 87 m³/day; • Soham WwTW – 782 m³/day; and • Bottisham WwTW is - 54 m³/day. These discharge values were calculated as a percentage of the flood flow for different return periods as shown in Table 3-6 below.

Return Period Stage 2 Water Cycle Study: Final Report Sept 2011 35 Cambridgeshire Horizons East Cambridgeshire – Detailed WCS Table 3-6: Additional flow from WwTW as a percentage of estimated flood flows Burwell Lode (Burwell WwTW) m³/day % additional flow of flood flow Soham Lode (Soham WwTW) Swaffham Bulbeck Lode (Bottisham WwTW) m³/day % additional flow of flood flow m³/day % additional flow of flood flow Q2 (QMED) 3629 2.41 221098 0.35 2246 2.38 Q5 5098 1.71 301882 0.26 3110 1.72 Q10 6048 1.45 350870 0.22 3802 1.41 Q20 7258 1.20 412042 0.19 4838 1.11 Q50 8294 1.05 457747 0.17 5789 0.93 Q100 9245 0.95 503971 0.16 6912 0.77 Q200 10368 0.84 550973 0.14 8208 0.65 Q500 11923 0.73 614563 0.13 10282 0.52 Q1000 13219 0.66 663898 0.12 13219 0.41 Based on these estimates the potential additional discharges to these WwTW are not significant (all less than 2.5% and the majority calculated to be less than 1%). It is considered unlikely that these additional flows would result in a significant increase in flood levels; however, this should be considered as part of any proposed upgrade works at the WwTWs. New Solution Requirements – No Deterioration The modelling results show that there are two wastewater catchments where deterioration from the current WFD waterbody status would result from the proposed growth and hence would require a new solution – these are: • Burwell (for phosphate); and • Bottisham (for ammonia). 21 Allocations and windfalls Burwell WwTW - Solution Phosphorus standards within the Burwell Lode will limit the total volume of effluent that can be discharged at this location. RQP modelling has shown that no further increases in flow from Burwell WwTW will be possible without deteriorating from the Good status for P even when treating at the limits of conventional treatment; an absolute requirement of the WFD is that there must not be a deterioration from the current status. With the information available to complete this assessment, it has been concluded that a new solution is required for the outstanding 191 homes that do not have planning permission 21 and 6.13 Ha of employment land.

Return<br />

Period<br />

Stage 2 <strong>Water</strong> <strong>Cycle</strong> <strong>Study</strong>: Final Report<br />

Sept 2011<br />

35<br />

<strong>Cambridgeshire</strong> Horizons<br />

<strong>East</strong> <strong>Cambridgeshire</strong> – <strong>Detailed</strong> WCS<br />

Table 3-6: Additional flow from WwTW as a percentage of estimated flood flows<br />

Burwell Lode (Burwell<br />

WwTW)<br />

m³/day % additional<br />

flow of flood<br />

flow<br />

Soham Lode (Soham WwTW) Swaffham Bulbeck Lode<br />

(Bottisham WwTW)<br />

m³/day % additional flow<br />

of flood flow<br />

m³/day % additional flow<br />

of flood flow<br />

Q2 (QMED) 3629 2.41 221098 0.35 2246 2.38<br />

Q5 5098 1.71 301882 0.26 3110 1.72<br />

Q10 6048 1.45 350870 0.22 3802 1.41<br />

Q20 7258 1.20 412042 0.19 4838 1.11<br />

Q50 8294 1.05 457747 0.17 5789 0.93<br />

Q100 9245 0.95 503971 0.16 6912 0.77<br />

Q200 10368 0.84 550973 0.14 8208 0.65<br />

Q500 11923 0.73 614563 0.13 10282 0.52<br />

Q1000 13219 0.66 663898 0.12 13219 0.41<br />

Based on these estimates the potential additional discharges to these WwTW are not<br />

significant (all less than 2.5% and the majority calculated to be less than 1%). It is considered<br />

unlikely that these additional flows would result in a significant increase in flood levels;<br />

however, this should be considered as part of any proposed upgrade works at the WwTWs.<br />

New Solution Requirements – No Deterioration<br />

The modelling results show that there are two wastewater catchments where deterioration from<br />

the current WFD waterbody status would result from the proposed growth and hence would<br />

require a new solution – these are:<br />

• Burwell (for phosphate); and<br />

• Bottisham (for ammonia).<br />

21 Allocations and windfalls<br />

Burwell WwTW - Solution<br />

Phosphorus standards within the Burwell Lode will limit the total volume of effluent that can be<br />

discharged at this location. RQP modelling has shown that no further increases in flow from<br />

Burwell WwTW will be possible without deteriorating from the Good status for P even when<br />

treating at the limits of conventional treatment; an absolute requirement of the WFD is that<br />

there must not be a deterioration from the current status.<br />

With the information available to complete this assessment, it has been concluded that a new<br />

solution is required for the outstanding 191 homes that do not have planning permission 21 and<br />

6.13 Ha of employment land.

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