’Sustainable Rural Wastewater Treatment in Rural Housing’ Presentation 1 02 08

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Presentation entitled ‘Sustainable Wastewater Management in Rural Housing Developments’ given on the 28th January, 2008 at the ESAI run Environ Colloquium 2008. For rural developments, it is …

Presentation entitled ‘Sustainable Wastewater Management in Rural Housing Developments’ given on the 28th January, 2008 at the ESAI run Environ Colloquium 2008. For rural developments, it is frequently the responsibility of private developers to identify a suitable wastewater treatment system to treat the effluent. Frequently, the capacity of adjacent streams and rivers to accept further treated effluent is reached and a discharge of treated effluent to groundwater is the only viable option necessitating the processing of a Discharge Licence Application and the carrying out of a groundwater assessment to assess the assimilative capacity of the underlying aquifer. Under the Nitrates Directive, the quality of treated wastewater being discharged to ground is of paramount importance in conjunction with the background nitrate concentration. This presentation was 0.3 hours in duration and hosted approximately 200 delegates

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  • 1. ESAI Colloquium, Dundalk Institute of Technology, Co. Louth, Ireland Sustainable Wastewater Management in Rural Housing Developments 3 rd February 2008 Padraic Mulroy, Managing Director Mulroy Environmental
  • 2.
    • Qualifications
      • BSc. Microbiology, (2:1), 1993 - NUIG;
      • MSc. (Major: Soil & Water Science &
      • Minor: Environmental Engineering)
      • - 1996, University of Florida, US.
    • Professional Affiliations
      • MIEI (Institute of Engineers)
      • IRCA (International Register of Certified Auditors)
    • Non-Professional Affiliations
      • IOWA (Irish On-site Wastewater Association)
      • IAH (International Association of Hydrogeologists)
    BACKGROUND ACADEMIC 1 Background 2 Guidelines 3 Legislation 4 Infrastructural Deficit 5 Discharge Licence Application Process 6 WWTP Solution 7 Case Study – Site ‘X’ 8 Conclusions
  • 3.
    • Capabilities
      • Wastewater Treatment Plant Design for Single, Small Community, Commercial & Industrial Development
      • Site Suitability Assessment
      • Due Diligence Site Investigation/Contaminated Land Risk Assessment
      • Remediation/Bioremediation of Contaminated Soil & Water
      • Waste Licence & Permit Applications
      • IPPC Licensing
      • Environmental Impact Assessment
      • Sludge Management Expertise
      • Strategic Environmental Assessment
      • Environmental Monitoring
    BACKGROUND MULROY ENVIRONMENTAL 1 Background 2 Guidelines 3 Legislation 4 Infrastructural Deficit 5 Discharge Licence Application Process 6 WWTP Solution 7 Case Study – Site ‘X’ 8 Conclusions
  • 4. GUIDELINES Local Authorities
    • ‘ Sustainable Rural Housing, Guidelines for Planning Authorities ’, DOELG, 2005:
    • Main drivers:
      • Ribbon development needed to be curbed;
      • Development should concentrate around rural villages;
      • Clustered approach to development to be encouraged; and
      • ‘ Wastewater treatment facilities in rural areas should therefore be located, constructed and maintained to the highest standards to ensure minimal impacts on water quality and particularly groundwater quality.’
    1 Background 2 Guidelines 3 Legislation 4 Infrastructural Deficit 5 Discharge Licence Application Process 6 WWTP Solution 7 Case Study – Site ‘X’ 8 Conclusions
  • 5. GUIDELINES Wastewater Treatment Plant Design & Site Assessment
      • EPA Manual, Treatment systems for Single Houses, 2000
      • Draft Code of Practice Wastewater Treatment Systems for Single Houses (PE<10)
      • EPA Manual, Treatment systems for Small Communities, Business, Leisure Centres and Hotels, 1999
      • BS5930, Code of Practice for Site Investigations.
    1 Background 2 Guidelines 3 Legislation 4 Infrastructural Deficit 5 Discharge Licence Application Process 6 WWTP Solution 7 Case Study – Site ‘X’ 8 Conclusions
  • 6. LEGISLATION
    • Water Pollution Act(s) 1977 & 1990
    • Water Framework Directive SI 772 of 2003
    • Nitrates Directive
    • Phosphorus Regulations Statutory Instrument 258 of 1998
    • Groundwater Directive as implemented by SI 271 of 1992
    • Protection of Groundwater Regs. (SI 41 of 1999)
    • Freshwater Fish SI 293 of 1988
    • Shellfish SI 200 of 1994 where discharge is either directly or indirectly to a shellfish area.
    • Quality of Salmonid Waters SI 293 of 1988
    • Bathing Water SI 155 of 1992 and 230 of 1996 where discharge is either directly or indirectly to a bathing area.
    • Surface Water Abstraction Regulation SI 294 of 1989
    • Quality of Surface water intended for abstraction of drinking waters SI 294 of 1989
    • Any relevant Water quality management plan
    1 Background 2 Guidelines 3 Legislation 4 Infrastructural Deficit 5 Discharge Licence Application Process 6 WWTP Solution 7 Case Study – Site ‘X’ 8 Conclusions
  • 7. LEGISLATION
    • Memorandum No 1 Technical Committee on Effluent and Water Quality Standards
    • EPA 1998 Environmental Quality objectives and Environmental Quality Standards
    • Any other relevant national Environmental Quality standards and objectives
    1 Background 2 Guidelines 3 Legislation 4 Infrastructural Deficit 5 Discharge Licence Application Process 6 WWTP Solution 7 Case Study – Site ‘X’ 8 Conclusions
  • 8. INFRASTRUCTURE DEFICIT
    • Wastewater Treatment Plants (WWTPs)
      • Existing Public WWTP may be at design capacity;
      • Local Authority do not have sufficient funds to upgrade or replace existing plant;
      • Private developer then advised to identify own solution to treat wastewater from development;
      • LAs are looking to Private Developers to ‘make up the deficit’
    1 Background 2 Guidelines 3 Legislation 4 Infrastructural Deficit 5 Discharge Licence Application Process 6 WWTP Solution 7 Case Study – Site ‘X’ 8 Conclusions
  • 9. DISCHARGE LICENCE APPLICATION PROCESS
    • When is a Discharge Licence Required?
      • All Industrial or Commercial Development discharging to surface waters or groundwater;
      • All Residential Development discharging to surface water; and
      • 8 houses or >5m 3 of effluent discharging to groundwater.
    1 Background 2 Guidelines 3 Legislation 4 Infrastructural Deficit 5 Discharge Licence Application Process 6 WWTP Solution 7 Case Study – Site ‘X’ 8 Conclusions
  • 10. WWTP SOLUTION
    • Preliminary Investigation/Desk Study
      • How big is the development (i.e. PE)?
      • Available footprint for WWTP?
      • Discharge of treated effluent - surface water or groundwater?
      • Surface Water
        • Adjacent surface water bodies to site?
        • Existing discharges to surface water body?
        • Liaison with Regional Fishery Board
      • Groundwater
        • Existing discharges to groundwater body?
        • Proximity of adjacent water abstraction wells?
        • GSI Well Database search
      • Review of Discharge Licence Application & Licence Database within Local Authority
      • Liaison with Local Authority & Local Area Engineer
      • Financial outlay – Recoup costs from development?
    1 Background 2 Guidelines 3 Legislation 4 Infrastructural Deficit 5 Discharge Licence Application Process 6 WWTP Solution 7 Case Study – Site ‘X’ 8 Conclusions
  • 11. WWTP SOLUTION
    • Surface Water
      • Capacity of surface water body?
        • Preliminary assessment during August, September & October indicates >10:1 Dilution – Yes
        • Correlated to nearby rated station - 95 %ile flow and Dry Weather Flow
        • LA and/or Fisheries Board may require Hydrometric station installation
      • Chemical/microbiological composition of the effluent & receiving surface water body
      • Biological assessment of receiving water body
      • Assessment of impacts of the proposed discharge on the chemical, biological and microbial quality on the surface water having consideration for relevant legislation
      • Main problem - Phosphorous Regulations specify a concentration of 0.015mg/l for Q5 River
      • Only MBR WWTP capable of consistent low P levels - 0.1mg/L to 0.5mg/L Orthophosphate-P - Cost?
      • Cumulative impact of P is a major concern for LAs & Fisheries Boards
  • 12. WWTP SOLUTION
    • Surface Water Discharge
    Size/Assimilative capacity? 1 Background 2 Guidelines 3 Legislation 4 Infrastructural Deficit 5 Discharge Licence Application Process 6 WWTP Solution 7 Case Study – Site ‘X’ 8 Conclusions
  • 13. WWTP SOLUTION
    • Surface Water Discharge
    1 Background 2 Guidelines 3 Legislation 4 Infrastructural Deficit 5 Discharge Licence Application Process 6 WWTP Solution 7 Case Study – Site ‘X’ 8 Conclusions
  • 14. WWTP SOLUTION
    • Surface Water Discharge
    Hydrometric stations – remote data logging & telemetry systems 1 Background 2 Guidelines 3 Legislation 4 Infrastructural Deficit 5 Discharge Licence Application Process 6 WWTP Solution 7 Case Study – Site ‘X’ 8 Conclusions
  • 15. WWTP SOLUTION
    • Surface Water Discharge
    1 Background 2 Guidelines 3 Legislation 4 Infrastructural Deficit 5 Discharge Licence Application Process 6 WWTP Solution 7 Case Study – Site ‘X’ 8 Conclusions
  • 16. WWTP SOLUTION
    • Groundwater DLA Requirements
      • Industrial & commercial - Harmful substances present in effluent 1 st & 2 nd Schedule of Protection of Groundwater Regs. (SI 41 of 1999)
      • The hydrogeology of the area in which the aquifer is located.
      • The risk of deterioration in the quality of the water to the entry of harmful substance
      • The risk to human health or water supplies, aquatic ecosystem or interference with the use of water for agriculture, commercial, domestic, fisheries, industrial or recreational purposes.
    1 Background 2 Guidelines 3 Legislation 4 Infrastructural Deficit 5 Discharge Licence Application Process 6 WWTP Solution 7 Case Study – Site ‘X’ 8 Conclusions
  • 17. WWTP SOLUTION
    • Groundwater DLA Requirements
      • Discharge is to a locally or regionally important aquifer, an examination of the aquifer in respect of extent, estimated volume of water and estimated rate of recharge required.
      • Nature, slope, thickness, particle size distribution, vulnerability, variations with depth and permeability of any overlying soil and subsoil
      • Permeability of bedrock
      • Depth to Groundwater, recharge estimates and hydraulic gradient
      • Existing Groundwater Quality
    1 Background 2 Guidelines 3 Legislation 4 Infrastructural Deficit 5 Discharge Licence Application Process 6 WWTP Solution 7 Case Study – Site ‘X’ 8 Conclusions
  • 18. WWTP SOLUTION
    • Groundwater DLA Requirements
      • Field Work Required
      • Trialpitting & percolation (T & P) tests
      • (i.e. Site Suitability Assessment standard)
      • 2 monitoring wells installed into bedrock aquifer – upgradient & downgradient of proposed discharge area
      • Short duration (2hr) constant discharge Pumping & Recovery Test
      • Wells & wastewater treatment systems inventory within 100 meters of proposed treatment plant or percolation area (500m preferable).
      • Each borehole sampled on 4 occasion over 1 month duration to calculate mean values
    1 Background 2 Guidelines 3 Legislation 4 Infrastructural Deficit 5 Discharge Licence Application Process 6 WWTP Solution 7 Case Study – Site ‘X’ 8 Conclusions
  • 19. WWTP SOLUTION
    • Groundwater DLA Requirements
      • Trialpitting – 3m minimum (5m preferable)
    1 Background 2 Guidelines 3 Legislation 4 Infrastructural Deficit 5 Discharge Licence Application Process 6 WWTP Solution 7 Case Study – Site ‘X’ 8 Conclusions
  • 20. WWTP SOLUTION
    • Groundwater DLA Requirements
      • T-Test & P-Test – run concurrently
    1 Background 2 Guidelines 3 Legislation 4 Infrastructural Deficit 5 Discharge Licence Application Process 6 WWTP Solution 7 Case Study – Site ‘X’ 8 Conclusions
  • 21. WWTP SOLUTION
    • Groundwater DLA Requirements
      • Drilling – Bedrock aquifer depth
    1 Background 2 Guidelines 3 Legislation 4 Infrastructural Deficit 5 Discharge Licence Application Process 6 WWTP Solution 7 Case Study – Site ‘X’ 8 Conclusions
  • 22. WWTP SOLUTION
    • Groundwater DLA Requirements
      • 2 Groundwater Monitoring Wells
    1 Background 2 Guidelines 3 Legislation 4 Infrastructural Deficit 5 Discharge Licence Application Process 6 WWTP Solution 7 Case Study – Site ‘X’ 8 Conclusions
  • 23. WWTP SOLUTION
    • Groundwater DLA Requirements
      • Monitoring Well – permanent installation
    1 Background 2 Guidelines 3 Legislation 4 Infrastructural Deficit 5 Discharge Licence Application Process 6 WWTP Solution 7 Case Study – Site ‘X’ 8 Conclusions
  • 24. WWTP SOLUTION
    • Groundwater DLA Requirements
      • Pump Testing – 4 hour duration
  • 25. WWTP SOLUTION
    • Groundwater DLA Requirements
      • Pump Testing
        • Drawdown Chart
  • 26. WWTP SOLUTION
    • Groundwater DLA Requirements
      • Pump Testing
        • Recovery Chart
  • 27. WWTP SOLUTION
    • Groundwater DLA Requirements
      • Hydraulic Flow Calculations
      • q = Kb (h1-h2)
      • L
      • = 1.26m 3 /day/metre of aquifer width
        • q = flow through each metre of aquifer width
        • K = hydraulic conductivity (i.e. Average of BH101 & BH102 = Xm/day)
        • h1-h2 = hydraulic head – difference in water level between upgradient and downgradient monitoring wells
        • L = flowpath distance – distance between upgradient and downgradient monitoring wells
        • b = aquifer thickness – this is taken as the depth of saturated aquifer
  • 28. WWTP SOLUTION
    • Groundwater DLA Requirements
      • Dilution of Effluent
    • Final Nitrate (as NO 3 -N) groundwater concentration =
    • (Effluent Concentration * Volume) + (Average Groundwater Conc. * Volume)
    • (Groundwater Volume + Effluent Volume)
  • 29. WWTP SOLUTION
    • Groundwater DLA Requirements
      • What’s acceptable to Local Authority?
        • Existing Nitrate levels in groundwater need to be low
        • Wastewater treatment plant needs to have proven
        • track record on nitrate removal
        • Cumulative impact on NO 3 -N levels need to be negligible
        • NO 3 -N levels in effluent need to be significantly lower than groundwater concentrations
  • 30. CASE STUDY – SITE ‘X’
    • 19-House Development
    • Population equivalent of 76P.E.
    • Total Daily Dry Weather Flow = 13,680 litres/day.
    13,680 DWF = 24 x 3600 = 0.158 l/s Peak Flow = 2.5 x 0.158 = 0.395 l/s
    • Organic Load @ 4.1kg BOD/day; and
    • Ammonia load @ 0.54kg NH 3 /day.
  • 31. CASE STUDY – SITE ‘X’
    • Solution
      • Submerged Membrane Bioreactor (125PE)
      • Mounded Stratified Sand Polishing Filter
          • Bedrock/Groundwater
  • 32. CASE STUDY – SITE ‘X’
  • 33. CASE STUDY – SITE ‘X’
  • 34. CASE STUDY – SITE ‘X’
  • 35.
    • CASE STUDY – SITE ‘X’
    • Soil Map
    TMp Rck
  • 36.
    • CASE STUDY – SITE ‘X’
    • Bedrock Map
    Dark Blue Grey Slate Green & Grey Slate
  • 37.
    • CASE STUDY – SITE ‘X’
    • Aquifer Map
    Ll Pl
  • 38.
    • CASE STUDY – SITE ‘X’
    • Vulnerability Map
  • 39. CASE STUDY – SITE ‘X’
          • Groundwater DLA Requirements
          • Trialpit Log
    1 Background 2 Guidelines 3 Legislation 4 Infrastructural Deficit 5 Discharge Licence Application Process 6 WWTP Solution 7 Case Study – Site ‘X’ 8 Conclusions
  • 40. CASE STUDY – SITE ‘X’
          • Groundwater DLA Requirements
          • Borehole Log
    1 Background 2 Guidelines 3 Legislation 4 Infrastructural Deficit 5 Discharge Licence Application Process 6 WWTP Solution 7 Case Study – Site ‘X’ 8 Conclusions
  • 41. CASE STUDY – SITE ‘X’
      • Groundwater DLA Requirements
      • Borehole Log
    1 Background 2 Guidelines 3 Legislation 4 Infrastructural Deficit 5 Discharge Licence Application Process 6 WWTP Solution 7 Case Study – Site ‘X’ 8 Conclusions
  • 42. CASE STUDY – SITE ‘X’
    • 125 PE Membrane Bioreactor
      • Effluent with low suspended solids
      • Complete sludge retention, can be operated at high MLSS and it minimises excess sludge production
      • Final effluent quality of 5:5:5 BOD:SS:NH3.
      • 4-log reduction in viruses (i.e. enterovirus and coliphage) and a 6-log reduction in bacteria.
      • Proven ability to reduce NO 3 levels to background levels
      • Phosphate removal system can be added (Ferric Sulphate precipitation)
      • Tertiary Treatment levels attained!
      • However, expensive and requires quarterly maintenance & sludge removal
    1 Background 2 Legislation/ Guidelines 3 DLA Process 4 Results 5 Source protection measures 6 Conclusions
  • 43. CASE STUDY – SITE ‘X’
    • Stratified Sand Filter
      • All indigenous soil removed to bedrock level (i.e. approximately 3.0 to 3.5m bgl) and replaced with stratified sand filters (i.e. alternative layers of sand and pea gravel)
      • Further reduction of orthophosphates but expected to saturate with time
      • Evidence of nitrification occurring which will reduce Ammonia levels further
      • Certain degree of removal by microbial community of further dissolved organic carbon compounds and subsequently BOD reduction
    1 Background 2 Legislation/ Guidelines 3 DLA Process 4 Results 5 Source protection measures 6 Conclusions
  • 44. CASE STUDY – SITE ‘X’ SUBMERGED MEMBRANE BIOREACTOR
  • 45. CASE STUDY – SITE ‘X’ SUBMERGED MEMBRANE BIOREACTOR
  • 46. CASE STUDY – SITE ‘X’ SUBMERGED MEMBRANE BIOREACTOR
  • 47. CASE STUDY – SITE ‘X’ MOUNDED STRATIFIED SAND FILTER
  • 48. CASE STUDY – SITE ‘X’ MOUNDED STRATIFIED SAND FILTER
  • 49. CASE STUDY – SITE ‘X’ MOUNDED STRATIFIED SAND FILTER
  • 50. CASE STUDY – SITE ‘X’ MOUNDED STRATIFIED SAND FILTER
  • 51. CONCLUSIONS (I.E. EXPERIENCE TO-DATE) 1 Background 2 Guidelines 3 Legislation 4 Infrastructural Deficit 5 Discharge Licence Application Process 6 WWTP Solution 7 Case Study – Site ‘X’ 8 Conclusions
      • WFD & Nitrate Directive are being enforced at Local Authority level with regard to the DLA Process:
        • Background NO 3 -N levels - levels greater than 25mg/l will be refused
        • Proposed WWTP capacity to reduce NO 3 -N levels
      • Best Performance Proprietary WWTP is Submerged Membrane Bioreactor
      • Best Hydraulic Solution would appear to be a Mounded Stratified Sand Polishing Filter
  • 52. CONCLUSIONS (I.E. EXPERIENCE TO-DATE) 1 Background 2 Guidelines 3 Legislation 4 Infrastructural Deficit 5 Discharge Licence Application Process 6 WWTP Solution 7 Case Study – Site ‘X’ 8 Conclusions
      • Technological & engineering solutions to comply with WFD and Nitrates Directive are available
      • Validation of WWTP Construction and on-going monitoring are required to ensure performance
      • Management of WWTP issues have arisen:
        • Malfunctioning Housing Estate Management Companies/Payment of Annual Maintenance Fees
        • Selling of property with planning permission & lack of awareness by buyer of WWTP specification
      • Costs incurred by Local Authority if Management Companies fail to manage WWTP correctly – need to be taken in charge
  • 53. CONCLUSIONS (I.E. EXPERIENCE TO-DATE) 1 Background 2 Guidelines 3 Legislation 4 Infrastructural Deficit 5 Discharge Licence Application Process 6 WWTP Solution 7 Case Study – Site ‘X’ 8 Conclusions