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