Dialogues template | XX.2019 1

10 March 2020

Nature-based Solutions for wastewater treatment in cities

Dr. Antonina TorrensFSUB-University Barcelona

BRASÍLIA - DF – BRAZIL III International Seminar on Nature based Solutions (NbS)The water challenge and cities

Brasilia | 10.03.2020 2

Index

1.NBS for water and wastewater management in cities

2.Nature-based technologies for sanitation

3.NBS experiences

4. Implementing NBS for sanitation in cities: challenges

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The NBS definition by the European Union states that these solutions

are "inspired and supported by nature, which are cost-effective,

simultaneously provide environmental, social and economic benefits

and help build resilience.

• With respect to water issues, NBS can achieve the following (according to the World

Water Development Report 2018 by UN-Water):

1. Use natural processes to enhance water availability (e.g., soil moisture retention,

groundwater recharge),

2. Improve water quality (e.g., natural wetlands and constructed wetlands to treat

wastewater, riparian buffer strips), and

3. Reduce risks associated with water‐related disasters and climate change (e.g.,

floodplain restoration, green roofs)

1. Nature-based solutions for water and sanitation management in cities

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Chemical and microbiological

contamination

Sanitary risk

Environmental risk

SANITATION PLANS

- centralised-decentralised?

- disposal-reuse?

- rainwater?

- sludge?

LEGISLATION

TECHNOLOGIES (WWTP)

WASTEWATER- MUNICIPAL- INDUSTRIAL- RUNOFF- AGRICULTURALetc..

WATER POLLUTION

1. Nature-based solutions for water and sanitation management in cities

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Integrating Nature into Urban Sanitation Services

Current centralised vs. future decentralised and NBS based concepts for urban sanitation. Source: F.Masi, A.Rizzo, M.Regelsberger (2018).

NBS includes:

- circular economy,

- resource-oriented,

- green

infrastructure,

- and ecosystem

services

approaches to

respond to sanitation

needs worldwide.

1. Nature-based solutions for water and sanitation management in cities

From centralized to decentralized sanitation

From grey towards green

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Natural technologies (“extensive technologies”, “soft technologies”, “non-conventional

technologies” or “sustainable technologies”) for wastewater treatment use natural, commonly

occurring self-treatment processes that take place in soil, water and wetland environments.

Soil and vegetation are directly involved in the processes, mainly through the formation of

favourable conditions for the development of microorganisms taking part in the treatment

process.

2. Nature-based technologies

Beside the particular treatment aimed at, NBS can provide a variety of

other vital ecosystem functions, some of which are wildlife habitat,

evapotranspiration and thus urban heat cooling, water storage and

management, recreation, landscaping, green in the built environment.

Social benefits.

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Comparison of conventional and

natural technologies

Conventional Natural

High energy expenditure:

electrical energy for oxidation

and mixing in reactors (higher

cost)

Little or no energy expenditure: Natural

energy (sunlight and occasionally wind

energy)

Advanced technological

equipment

Little or no advanced technological

equipment. Ground movements in

construction are vital

Proportionally lower surface area Require considerable surface area

Short hydraulic retention time Long hydraulic retention time

Processes may be rapidly

modified

Treatment mechanisms have

considerable inertia

Complex maintenance and

exploitation

Simple maintenance and exploitation

Specialized labour supply Management should know the

processes and be able to prevent

problems

Technological appearance Good integration in landscape

Artificial processes (very

accelerated systems)

Natural processes at “natural” speeds

2. Nature-based technologies

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Water based (algae/plants): ponds

- Naturals

• anaerobic, facultative, maturation, storage

• macrophyte pond

- Aerated pond

Wetland based: constructed wetlands

- Natural

• Free water surface flow

• Subsurface flow

o horizontal

o vertical (conventional, “French”)

o Hybrid

• Intensified Systems (eg. aerated)

Soil /soil-plant based

- Infiltration-percolation

- Soil-plant aquifer treatment

- Soil-plant-aquifer treatment

- Green walls and green roofs

Types

2. Nature-based technologies

Alone, combined or combined with conventional

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Legislation

Governance

Environmental

aspects

Economical

constraints

Technical

aspects

Climatic

constraints

Sociological

constraints

WWT technology:

choice

Availability

of land

Geological

constraints

Technology choice

2. Nature-based technologies

Type of

wastewater

Disposal/reuse

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Applications

2. Nature-based technologies

Domestic wastewater (black, grey)

Urban wastewater (small medium size communities):

secondary treatment of municipal wastewater

Urban wastewater: tertiary treatment as polishing stage

in conventional treatment plants or other natural

systems (eg. big cities)

Industrial wastewater

Agro industrial wastewater

Agriculture source wastewater

Runoff water

Sewage overflow

Sludge

Landfill

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Costs and energy requirements2. Nature-based technologies

Constructed Wetlands vS conventional technological

solutions - Investment and O&M costs

Comparison among

investment costs of

CW and activated

sludge WWPTs on the

basis of Italian

experience (IRIDRA's

analysis)

O&M cost

comparison

between CW and

activated sludge

WWTPs on the

basis of Italian

experience

(IRIDRA's analysis)

Comparison of energy consumption for

different conventional and nature-

based treatment technologies

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French Subsurface Flow Constructed Wetlands for raw wastewater treatment

(towns and neighborhoods <20.000 PE)

“French reed beds”

FRB is an attractive solution to minimize the operational andmaintenance (O&M) costs of wastewater treatment.

Schematic of french VFCW

3. Nature-based solutions experiences

WWTP of Orhei municipality (20000 PE)Moldavia, among the biggest CW systemworldwide.

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Residential area in

Preganziol (Italy)

Nature based solutions for the treatment and reuse of grey water

(decentralized sanitation in buildings or condominiums)

Constructed wetlands

3. Nature-based solutions experiences

Telaviv (Israel) Grey water for toilet flushing;

rain water harvesting and reuse

for irrigation

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Green walls (vertical gardens)

3. Nature-based solutions experiences

Greywater green wall by Vivers Ter-Asepma.

2.500 m2 vertical garden at the Tabacalera

Space in Tarragona (Spain).

Nature based solutions for the treatment and reuse of grey water

(decentralized sanitation in buildings or condominiums)

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Ponds for wastewater treatment and reuse of small-medium-large cities

3. Nature-based solutions experiences

Pond systems: Ouagadougou WWTP (Burkina Faso)Treating 96 m3/h of domestic and industrial wastewater

Reuse in periurban gardens

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Infiltration-percolation for wastewater reclamation

3. Nature-based solutions experiences

Infiltration-

percolation for

tertiary treatment,

Palamós, Spain

Infiltration-percolation

for secondary

treatment, Hostalets

de Pierola, Spain

Drip irrigation

Infiltration-

percolation pilot

for car-washing

wastewater

recycling

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Aerated constructed wetlands for urban, industrial wastewater and combined sewer overflow

treatment

Aerated CW for WWTP of Merone (CO-120.000 PE). The

centralised WWTP of Merone treats the wastewater from

the combined sewer serving 38 towns.

3. Nature-based solutions experiences

Combined sewer overflow upstream the WWTP of Merone (Italy)

Aerated wetland of 360 m², treating the sanitary waste

water from an elementary school, Bretch (Belgium)

The school has 700 students and 300 personnel

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Environmental problems of the final

stretch of the Besòs river.

▪ Very degraded and high

marginality

▪ Problems with the hydraulic

capacity

▪ Water pollution. High concentration

of nutrients in the river water.

▪ Polluted soils, the river use as a

brown field.

▪ No biota

▪ Citizens saw the river as a problem,

no connectivity between river sides

▪ No big green areas in this part of

the metropolitan area

Environmental Recovery of the final stretch of the River Besòs, Barcelona, Spain

3. Nature-based solutions experiences

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The general objectives of this recovery project

were:

Improve the environmental and landscape

quality of the watercourse.

Improve the flow from the Montcada i

Reixac wastewater treatment plant through

the introduction, in the watercourse, of a

tertiary treatment based on the generation

of wetlands.

Guarantee the hydraulic capacity of the

river.

Recover and naturalize the final section of

the mouth.

Use certain spaces of the river for leisure.

Environmental Recovery of the final stretch of the River Besòs, Barcelona, Spain

3. Nature-based solutions experiences

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Key features Project implemented in three phases:

Withdrawal of 69 high tension towers and its bases (2002-

2006)

Restoration of 9.2 km (5mi 1261.2yd) from the river.

Total budget: 40.5 million € 85% funded by the EU

(Cohesion Funds)

Social Success. More than one million visitors/year

Improved environmental conditions: more than 160 bird

species. aprox. 10 ha of wetlands / 3,8 Km with water

tertiary treatment

60 treatment beds (plots) grouped into 15 groups

1.000 m3/h of water treated / 30% of the effluent from

the Montcada waste water treatment plant

Treatment flow rate for the beds as a whole be between

0,3-0,4 m3/s (depending on natural conditions)

In operation since: Dec 2007

Environmental Recovery of the final stretch of the River Besòs, Barcelona, Spain

3. Nature-based solutions experiences

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Constructed wetlands in Besòs river

Environmental Recovery of the final stretch of the River Besòs, Barcelona, Spain

3. Nature-based solutions experiences

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Environmental Recovery of the final stretch of the River Besòs, Barcelona, Spain

3. Nature-based solutions experiences

Brasilia | 10.03.2020 23

Environmental Recovery of the final stretch of the River Besòs, Barcelona, Spain

3. Nature-based solutions experiences

Brasilia | 10.03.2020 24

Environmental Recovery of the final stretch of the River Besòs, Barcelona, Spain

3. Nature-based solutions experiences

Brasilia | 10.03.2020 25

Environmental Recovery of the final stretch of the River Besòs, Barcelona, Spain

3. Nature-based solutions experiences

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How to integrate NBS for WASTEWATER treatment IN the City?

Challenges

Space needed per PE

Legislation

Governance

Risk

Public acceptance (e.g. odours)

Incorporate into urban planning

4. Implementing NBS for sanitation in cities: challenges

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10-03-2020

Obrigada!

antoninatorrens@ub.edu