Jonathan Bishop, Middle East Unit Water and Wastewater Process Manager

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Advances in Wastewater The Benefits to the GCC
Region

• Jonathan Bishop, Middle East UnitWater and
  Wastewater Process Manager

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Introduction

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

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Odour Control
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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

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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
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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.

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Odour- Control, Treatment and Abatement

• 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

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Odour- Control, Treatment and Abatement
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Anaerobic Digestion
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What is Anaerobic Digestion?

• Conversion of organic matter to methane and
  carbon dioxide in the absence of oxygen.
• C5H702N6H20 5CH4 2NH3 5CO2 Biogas
• Produces stabilised residual solids.
• Biogas comprises approximately 60 to 65CH4, 30
  to 35CO2 and other gasses.

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Typical AD system

• Effective gas mixing
• Effective external heat exchangers
• 15 day retention
• Continuous feeding

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Enhanced AD System

• Effective jet mixing
• Effective external heat exchangers
• 12 day retention
• Continuous feeding

Pre-treatment
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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

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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
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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
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Methods of Pre-treatment

• Biological
• Thermal
• Chemical
• Mechanical (high shear, grinding)
• Ultrasonic

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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
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Case Study-Kings Lynn STC, United Kingdom

• Sludge Throughput 14,500 to 19,000tDS/year
• Proportion of primary to WAS 5050 to 3565
• Pre-treatment Biological
• Volatile Solids Destruction 50 to 60

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

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Nutrient Removal
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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

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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.

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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

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Nutrient Removal - Nitrate
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Various Process ConfigurationsBiological
Nutrient Removal
Johannesburg Process
5 stage Bardenpho process
Modified University of Cape Town (MUCT)
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Tender Design
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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

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Detailed Tender Design

• Close collaboration between all parties in 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

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