Next generation wastewater treatment
Craig CriddleCivil and Environmental EngineeringStanford University March 31, 2011
San Francisco Bay• The San Francisco Bay is
protected by 40 treatment wastewater treatment plants
• All are currently involved in master planning to revitalize their wastewater treatment systems
• The effects of regional resource recovery could be dramatic
Water (99.9%) Biodegradable Organics Nutrients (N and P)
Pathogens Salt Refractory Organics
Resources
Impurities
Wastewater as a Resource
Resource Per m3
US $ per m3
Organic Soil Conditioner (kg) 0.10 0.03
Methane (m3) 0.14 0.07
Nitrogen (kg) 0.05 0.07
Phosphorus (kg) 0.01 0.01
Water (1 m3) 1.00 0.33
The Value of the Resource
Source: Willy Verstraete (2008)
In reality, the value of the resources depends on:
Cost of recovering it
Cost of adding value to it
Cost of transporting the value-added resource
The sale price
Sale price
11 kg methanol $4.50$0.43/kg
catalytic2 kg fish food $2.00
$1.00/kgbiological
5.3 kg methane 1 kg bioplastic $4.70$4.70/kgbiological
0.2 MBTU ~$0.80$4.10/MBTU
thermal
Resource recovery can be tailored to local markets and ecosystems requirements.
The Stanford-Palo Alto Water Team
FrankJoshTom
Phil
Craig
Marty
Eun Jung
Sebastien
Weimin
David
Sandy
Scale
• Building: A set of rooms with shared drainage; includes
–Hotels–Dorms–Houses
Stanford Living Innovation Center
(Green Dorm)
Cluster: A collection of buildings with a shared drainage line for wastewater collection; includes
Small citiesHOAsCampusesFarms
Stanford Campus
Catchment: A region defined by the set of all clusters with a shared drainage system; includes
Cities with a shared treatment facility and shared storm drainsFarms with shared drainage
Catchment of the City of Palo Alto
Watershed: A region defined peripherally by a divide and draining to a particular water body; the set of all catchments within a drainage basin
San Francisco Bay Watershed
Scale
Stanford Living Innovation Center
(Green Dorm)
Stanford Campus
Catchment of the City of Palo Alto
San Francisco Bay Watershed
Energy for Transportof Water to User
High
Low
< 200 MJ/m3
200-1000 MJ/m3
Approach
• Determine baseline water balances at each scale
• Determine baseline energy audits at each scale
• Identify appropriate technologies at each scale
• Conduct a cost benefit analysis to assess technologies and costs across scale
Reuse or Receiving Water BodyTreatment Plant
Catchment
Buildings at Nodes
Clusters
Building Scale
Why Recover Water and Other Resources
at the Building Scale?
• It is the point closest to the demand for water; pumping energy will be lowest and pipe length will be shortest
• Dilution of resources in the water will be least; source separation may be possible.
• Could we recover pharmaceuticals?
What Technologies Might Make Sense at the Building Scale?
• Greywater treatment and reuse?• Rainwater harvesting?• Energy recovery from wastewater and organic
solid wastes (restaurants, dining halls, etc.)?• Source separation and collection (metals and
organics at manufacturing facilities, urine, etc.)?
Application: Stanford Green Dorm
• Greywater treatment and reuse• Rainwater harvesting
0.01 MG
1.10 MGIndoor Demand
0.62 MGSFPUC
0.74 MG
0.20 MG
0.6 MG 0.10 MG
0.50 MG
0.10 MGEvapotranspiration
0.04 MG Roof Runoff
0.08 MG Evapotranspiration
0.08 MG Rain
0.04MGLeakage
0.07 MG Landscaping Water
0.03 MG Pervious Runoff
0.01 MG Evaporationfrom Roof
0.05 MGLeakage and Domestic Use
Stormwater
0.01 MG
0.03 MG
0.01 MG
Sewer
Condenser
0.35 MGBlackwater
0.74 MG Greywater
Projected Annual Water Balance
% Demand Met by Recycled & Collected Water
Outdoor: 100%Greenhouse: 100%Indoor: 48%Overall: 58%
% Demand Met by Recycled & Collected Water
Outdoor: 100%Greenhouse: 100%Indoor: 48%Overall: 58%
Cluster Scale
Example: Stanford Campus
Imported (SFPUC)
Wastewater
Groundwater
Surface Water
Stanford University
Cluster
Potential Resource
Water Balance
Units are MGD From Stanford Utilities
Losses & domestic use
0.5 0.7 2.31.7
Landscape
0.4
Cooling
1.21.2
0.2
0.01
Imported (SFPUC)
Groundwater
Surface Water
Stanford University
Cluster
Water Balance (50% reuse scenario)
Units are MGD From Stanford Utilities
Losses & domestic use
0.5 0.1 1.71.7
Landscape
0.4
Cooling
0.60.6
0.2
0.61
Discharge to sewer decreased by 50%.
Can either decrease imported water by 36% OR decrease groundwater use by 86%.
% landscape demand met by recycled & collected water = 35%
Discharge to sewer decreased by 50%.
Can either decrease imported water by 36% OR decrease groundwater use by 86%.
% landscape demand met by recycled & collected water = 35%
Why Recover Resources at the Cluster Scale?
• For many clusters, energy for pumping will be less and pipe lengths will be shorter than from centralized treatment systems
• Recovered water may contain less salt than at centralized facilities
• Sea-level rise could flood some centralized facilities
• Compact systems with remote monitoring now feasible
What Might Make Sense at the Cluster Scale?
• “Scalping”: Extracting clean water from wastewater for local reuse?
• Energy extraction from organics?• RO to remove salt for some applications with
reuse of retentate
Ecosystem Restoration
Water UseAquifer Storage
Cooling
Washing Clothes
Flushing Toilets
Agriculture
Landscape
Salt Removal
Process for local recovery or send to sewer
Sewer
Process for local recovery or send to sewer.
Nutrient Removal
Scalping with Distributed Treatment
Process residuals for local energy recovery or send to sewer
Carbon Removal
Advanced Oxidation
Ocean
Treatment Plant
Scalping Facilities
Harvest Water
Scalping Facilities for Water Recovery and Local Reuse
Critical Technologies at the Cluster Scale
• Highly efficient separators to remove solids• Reactors for low-energy removal of organics • Advanced oxidation• Distributed monitoring and control
Example: Palo Alto Catchment
Palo Alto Treatment Plant
Catchment ScaleCatchment Scale
Los Altos ClusterLos Altos Cluster
Mountain View ClusterMountain View Cluster
Palo Alto ClusterPalo Alto Cluster
Stanford Cluster Stanford Cluster
East Palo Alto ClusterEast Palo Alto Cluster
Los Altos Hill ClusterLos Altos Hill Cluster
Palo Alto CatchmentWastewater Treatment PlantPalo Alto CatchmentWastewater Treatment Plant
Imported Water34 MGD
Groundwater 2.9 MGD
Surface Water 0.5 MGD
Discharge to Bay24 MGD
Palo Alto Catchment Water Balance
Palo AltoPalo Alto
Los AltosLos Altos
Mountain ViewMountain View
Stanford University Stanford University
East Palo AltoEast Palo Alto
Los Altos HillsLos Altos Hills
Palo Alto Catchment Wastewater Treatment(Concentrated 2X)
Palo Alto Catchment Wastewater Treatment(Concentrated 2X)
Imported Water24 MGD(29% Decrease)
Groundwater 0.3 MGD(90% Decrease)
Surface Water0.5 MGD
Discharge to Bay12 MGD(50% Decrease)
What Happens with 50% Reuse?
The Value of the Energy and Nutrients Arriving at the Centralized Facility Becomes Equivalent to That of the Water
x 2 =$0.36 per m3
How Does Resource Value Change at Centralized Facilities If Clusters Reuse 50% & Return Solids to the Sewer?
ResourcePer m3
US $ per m3
Organic Soil Conditioner (kg) 0.10 0.03
Methane (m3) 0.14 0.07
Nitrogen (kg) 0.05 0.07
Phosphorus (kg) 0.01 0.01
Water (1 m3) 1.00 0.33
Resource Per m3
US $ per m3
Organic Soil Conditioner (kg) 0.20 0.06
Methane (m3) 0.28 0.14
Nitrogen (kg) 0.10 0.14
Phosphorus (kg) 0.02 0.02
Water (1 m3) 1.00 0.33
Ocean
Treatment Plant
salt
Scalping Facilities
Harvest Water in Clusters
Harvest Water, Energy, Nutrients in Catchment
Centralized Facilities for Water, Carbon and Nitrogen Recovery
Energy Use at the Palo Alto Treatment Plant (Built in the 1970s)
High energy inputs for incinerator!
Total = 3,300 MJ/1000 m3
198 MJ
396 MJ
429 MJ
132 MJ
132 MJ
66 MJ
1914 MJ
A Typical Wastewater Treatment Plant Uses 1,200–2,400 MJ/1000 m3
33 MJ
Energy in Sewage
6,000 MJ/1000 m3
1,000 MJ/1000 m3
From combustion of reduced carbon (organics)
From combustion of reduced nitrogen (ammonia)
~7,000 MJ/1000 m3 total
Recall that a Typical Wastewater Treatment Plant Uses 1,200–2,400 MJ/1000 m3
Flared methane
Conventional digesters
Egg-shaped digesters in Singapore: designed to improve mixing and ease of solids removal
Anaerobic digesters
Gasification• Partial oxidation of biosolids at low oxygen levels
to produce syngas comprised of mainly CO, H2 and CH4
• Energy can be recovered in the syngas which can be used in an internal combustion engine for producing electricity or thermal oxidizer
• Only residuals is ash (2-4%)• Ability to co-gasify other organic carbon sourcesAbility to co-gasify other organic carbon sources• Technology is somewhat capital intensive
MaxWest Gasifier at Sanford, FL
Nitrous oxide0.5N2O
Destroys N2O, produces energy, and saves oxygen!
0.5N2+ 0.25O2 + 41 kJ
Ammonia NH3
1.0 O2
Can we also recover energy from the nitrogen?
What new treatment trains might make sense at centralized facilities?
HypotheticalResourceRecoveryCentralized Process Train
Wastewater
Enhanced primary treatment
Adv Oxid
Water for sale
O3
Filter / RO
brine
ocean
This process train emphasizes recovery of energy, water for reuse, and inorganic solids production only.
O2
GasifierAsh H2/COSN2Concrete
additiveor soil amendment
CO2
O2
Energy for sale
Solid Organic Waste Streams
Anaerobic treatment
CH4/CO2
Energy for sale
CO2
O2
Dewater solids
Low DO N removalP removal
O2
N2O
N2 + ½ O2
Fe (III)
But converting existing systems will require baby steps.
Existing Plant (Anywhere, USA)
Wastewater
Primary treatment Tricklin
g filter
Activated Sludge Nitrification
O2
Filtration UV Ocean
Thicken solids
O2
IncineratorCH4CO2
Ash
Landfill
O2
Hypothetical Baby Step 1: Enhanced Primary
Wastewater
Enhanced Primary treatment
Trickling filter
Activated Sludge Nitrification
Filtration UV Ocean
Thicken solids
O2
IncineratorCH4CO2
Ash
Landfill
O2
O2
Hypothetical Baby Step 2: Digester to Incinerator
Wastewater
Enhanced Primary treatment
Trickling filter
Activated Sludge Nitrification
Filtration UV Ocean
Thicken solids
O2
Anaerobic digester CH4/CO2
Dewater solids
Compost solids
To Activated Sludge Nitrification
Soil amendment
O2
Incinerator CO2
Ash
Landfill
O2
Hypothetical Baby Step 3:Digester only
Wastewater
Enhanced Primary treatment
Trickling filter
Activated Sludge Nitrification
O2
Filtration UV Ocean
Thicken solids
O2
Anaerobic digester CH4/CO2
CO2Energy for sale
Dewater solids
Compost solids
Liquid to Activated Sludge Nitrification
Soil amendment
O2
Hypothetical Baby Step 4:Anammox
Wastewater
Enhanced Primary treatment
Trickling filter
Activated Sludge Nitrification
O2
Filtration UV Ocean
Thicken solids
O2
Anaerobic digester CH4/CO2
CO2Energy for sale
Dewater solids
Compost solids
Soil amendment for sale
Anammox
To Activated Sludge Nitrification
O2
N2
Hypothetical Baby Step 5:More Anaerobic Treatment
Wastewater
Enhanced Primary treatment
Filtration UV Ocean
Thicken solids
Anaerobic digester CH4/CO2
CO2Energy for sale
Dewater solids
Compost solids
Soil amendment for sale
Anaerobic treatment
CH4/CO2
Energy for sale
O2
Activated Sludge Nitrification
O2
Anammox
To Activated Sludge Nitrification
O2
N2
Hypothetical Baby Step 6:Bio N removal
Wastewater
Enhanced Primary treatment
Bio N removal
O2
Filtration UV Ocean
Thicken solids
Anaerobic digester CH4/CO2
CO2Energy for sale
Dewater solids
Compost solids
Soil amendment for sale
Anammox
To Bio N removal
N2
Anaerobic treatment
CH4/CO2
Energy for sale
O2
CH3OH
O2
N2
Hypothetical Baby Step 7:Integrated solid waste
Wastewater
Enhanced Primary treatment
Bio N removal
O2
Filtration UV Ocean
Thicken solids
Anaerobic digester CH4/CO2
CO2Energy for sale
Dewater solids
Compost solids
Soil amendment for sale
N2
Anaerobic treatment
CH4/CO2
Energy for sale
O2
CH3OH
Solid Organic Waste Streams
(food wastes, grease, yard wastes, etc.)
Anaerobic digester (hydrolysis)
Anaerobic digester (hydrolysis)
Anammox
To Bio N removal
O2
N2
Hypothetical Baby Step 8:Methanol production
Wastewater
Enhanced primary treatment
Anaerobic digester
Bio N removal
O2
Water for sale
brineThicken solids
ocean
N2
O2
CH3OH
Solid Organic Waste Streams
(food wastes, grease, yard wastes, etc.)
CH4/CO2
Dewater solids
Anaerobic digester (hydrolysis)
Anaerobic digester (hydrolysis)
Biofuel for sale
Anammox
To Bio N
Compost solids
To thickener
Soil amendment for sale
Anaerobic treatment
CH4/CO2
Energy for sale
O2
Filtration UV
Possible future technology
Or might use Anammox here to eliminate methanol requirement
Hypothetical Baby Step 9:RO/Advanced oxidation
Wastewater
Enhanced primary treatment
Anaerobic digester
Bio N removal
O2
Filter / ROAdv Oxid
Water for sale
O3
brineThicken solids
ocean
N2
O2
CH3OH
Solid Organic Waste Streams
(food wastes, grease, yard wastes, etc.)
CH4/CO2
Dewater solids
Anaerobic digester (hydrolysis)
Anaerobic digester (hydrolysis)
Biofuel for sale
Anammox
To Bio N
Compost solids
To thickener
Soil amendment for sale
Anaerobic treatment
CH4/CO2
Energy for sale
O2
SupportWoods Institute for the Environment, Stanford UniversityCity of Palo Alto Stanford UtilitiesCal EPA
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