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Advances in Wastewater – The Benefits to the GCC Region

Jonathan Bishop , Middle East Unit Water and Wastewater Process Manager. Advances in Wastewater – The Benefits to the GCC Region. Introduction. Odour Control Anaerobic Digestion Enhanced Treatment Nutrient removal Ammonia – standard in region Total Nitrate Phosphate

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Advances in Wastewater – The Benefits to the GCC Region

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  1. Jonathan Bishop, Middle East UnitWater and Wastewater Process Manager Advances in Wastewater – The Benefits to the GCC Region

  2. Introduction • Odour Control • Anaerobic Digestion • Enhanced Treatment • Nutrient removal • Ammonia – standard in region • Total Nitrate • Phosphate • Biological Nutrient Removal • Recent Case Study

  3. Odour Control

  4. Odour • Result of biological activity on proteins and other substances in the wastewater in the absence of oxygen • Odorants generated comprise volatile organic compounds and gaseous inorganic compounds such as hydrogen sulphide (H2S) and ammonia (NH3) • Major sources of odour at typical wastewater treatment facilities include: • Pumped Sewers • Inlet Works including screens • Primary Settlement Tanks/Clarifiers • Sludge and return liquor treatment areas

  5. Odour- Analysis and Predictions • Dispersion models required to convert measured or calculated odour emission rates to atmospheric odour concentrations • 2 popular models available – AERMOD and ISC • AERMOD is recommended by the US EPA • AERMOD requires terrain and meteorological data for accurate predictions. Graphical Model Interface

  6. Odour- Analysis and Predictions • Model outputs are in the form of diagrams showing likely (98 percentile) atmospheric odour concentrations. • Wind roses show prevalent wind direction for the area under assessment.

  7. Dedicated Odour Control and Abatement Equipment include: Dry absorbers such as carbon filters Bio-filters and Bio-scrubbers that utilise biomass on a structured media bed. Chemical Scrubbers that utilise acids/alkalis and oxidants. Incinerators or thermal oxidisers that oxidise odorants in foul air. Masking Sprays may also be used to mask Odour- Control, Treatment and Abatement

  8. Odour- Control, Treatment and Abatement

  9. Anaerobic Digestion

  10. What is Anaerobic Digestion? Conversion of organic matter to methane and carbon dioxide in the absence of oxygen. C5H702N+6H20 5CH4 + 2NH3 + 5CO2 + Biogas Produces stabilised residual solids. Biogas comprises approximately 60 to 65%CH4, 30 to 35%CO2 and other gasses.

  11. Typical AD system • Effective gas mixing • Effective external heat exchangers • 15 day retention • Continuous feeding

  12. Enhanced AD System • Effectivejetmixing • Effective external heat exchangers • 12 day retention • Continuous feeding Pre-treatment

  13. What does Pre-treatment do? • Increase pathogen destruction • Compliance with microbial standards eg US EPA Class A • Safe use of sludge in agriculture • Applicable to wider range of crops • Secure agricultural disposal route • Increase solids destruction • Increased Bio-Gas production • Increased power generation through CHP • Reduced amount of sludge requiring disposal

  14. Reaction Steps in AD slowest step Step 1: hydrolysis starch  sugars Step 2: acidification sugars  VFAs Step 3: acetogenesis VFAs  acetates Step 4: methanogenesis acetates  biogas

  15. Reaction Steps in AD with Pre-Treatment pre-treatment AD hydrolysis hydrolysis pH = 5.0 to 5.5 acidification acidification pH ~ 7.0 to 7.5 acetogenesis methanogenesis

  16. Methods of Pre-treatment • Biological • Thermal • Chemical • Mechanical (high shear, grinding) • Ultrasonic

  17. Typical Biological System cold water raw sludge 55oC Ht Ex 3 42oC 42oC 42oC 55oC pre-treated sludge to AD reactor 55oC Ht Ex 1 Ht Ex 2 total retention = 2 days hot water

  18. Case Study-Kings Lynn STC, United Kingdom • Sludge Throughput = 14,500 to 19,000tDS/year • Proportion of primary to WAS = 50:50 to 35:65 • Pre-treatment = Biological • Volatile Solids Destruction = 50 to60%

  19. Case Study-Kings Lynn STC, United Kingdom Enough power generated to support the Wastewater Treatment Plant and export to the grid

  20. Why Adopt AD in the GCC? • Slow uptake of anaerobic technologies in the region. • WHY? • Cheap Energy - More expensive to recover energy from anaerobic digestion than have energy supplied from the grid/other sources. • BUT • Landfill - There will eventually be constraints on space for landfills which is currently the preferred disposal route for sludge solids • OTHER POSSIBLE DRIVERS • Fertiliser - Anaerobically digested sludge solids could be used as fertiliser if appropriate legislation and regulations are in place. • Sustainable - Sustainable source of energy.

  21. Nutrient Removal

  22. Nutrient removal - Introduction • Essential nutrients for plant growth: • Nitrogen – Ammonia, Nitrate • Phosphorous in the form of Orthophosphate • Nutrients are usually limited in natural waters and hence restrict plant and algae growth • Free fertiliser where TSE is re-used to irrigate plants

  23. Why use nutrient removal in GCC? • Chlorine disinfection – Ammonia removal required • Coastal discharges • Prevention of eutrophication where: • TSE is re-used for lakes and water features • Storage in lagoons is primary disposal outlet for TSE.

  24. Nutrient Removal – Ammonia • Most plants in region are designed to meet re-use standards • Normally will also achieve ammonia removal as well • Typically ammonia is converted to nitrate via nitrification • Requirements for Nitrification: • Typical Feed to Mass (F/M) Ratio = 0.15. This value increases with temperature

  25. Ammonia (NH3+) Aerobic Cycle(Air + Food) Ammonia Oxidising Bacteria(AOB) Nitrite Oxidising Bacteria (NOB) Nitrite(NO-) Nitrate(NO2-) Anoxic Cycle(Food) Nitrogen(N2) Nutrient Removal - Nitrate

  26. Various Process ConfigurationsBiological Nutrient Removal Johannesburg Process 5 stage Bardenpho process Modified University of Cape Town (MUCT)

  27. Tender Design

  28. Background • Leightons Middle East were bidding major Watewater Project in the Region • Mott MacDonald were commissioned to provide a detailed tender design covering all aspects of the project including: • Civil / Structural • Geo-technical • Process • Mechanical • Electrical and ICA

  29. Detailed Tender Design • Close collaboration between all partiesin the tendering team • Clearly defined extent of design responsibilities between all parties involved • Use of design examples / experience gained during execution of similar project elsewhere within Mott MacDonald • A detailed tender design was produced making use of the skills of all parts of the team • Good understanding of risks associated with the project and providing greater cost certainty to contractor and ultimate client • Detailed tender stage work would facilitate rapid start following award. • Key Design aspects include: • Carrying out engineering calculations for all structures and systems • Preparation of 3D Modelling of key structures

  30. www.mottmac.com

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