Sistemas naturales (alternativas) para el tratamiento de aguas (residuales)

Version 3

SWITCH Taller de CapacitaciónSan José, Costa Rica, 23 de noviembre 2010

Diederik Rousseau & Tineke Hooijmanswith inputs from Peter van der Steen

Natural treatment systems: response to main pressures

NATURAL TREATMENT SYSTEMS

SPACE REQUIREMENT

Climate Change

More floods More droughts

Stormwater management

BUFFERING CAPACITY

TREATMENT and REUSE

LOW ENERGY INPUT

Energy Reduction Urban Planning

Alternative water sources

Population growth

NUTRIENT RECYCLING

Food production(fertiliser)(water)Wastewater

management

Nhapi and Gijzen (2005)

STEP 1

POLLUTION PREVENTION AND MINIMISATION

• reduce water use

• reuse grey water

• ban undesirable compounds (toxicants)

• apply rainwater harvesting

STEP 2

TREATMENT IN THE DIRECTION OF REUSE

• convert waste to useful products (biogas, protein)

• optimize effluent reuse

STEP 3

DISPOSAL WITH STIMULATION OF SELF-PURIFICATION

• buffer strips

• floating wetlands

Water resource

NATURAL TREATMENT

SYSTEMS

3-Step Strategic Approach

Constructed wetland on the isle of Texel (NL) for further polishing of tertiary treated wastewater and ecological upgrading (Water

Harmonica concept) (Toet, 2003)

Benefit 1: Water reuse

Culemborg (Utrecht)The Netherlands

Benefit 1: Water reuse

Nutrients

PlantsAlgae

Periphyton

FishDucks

• Ornamental value• Mulching and composting• Pulping fibers• Silaging fodder• Proteins, food supplements

Benefit 2 - Nutrient reuse

Table 2.4. Economic efficiencies described as monthly profit per 1000 m2of current waste-water based farming systems in HCMC compared to traditional paddy rice farming.

Type of (wastewater) farming system Monthly profit per 1000 m2 Traditional paddy rice farming D$215,300 Wastewater-based water morning-glory D$320,000 Wastewater-based lotus monoculture farming D$440,000 Wastewater-based integrated lotus and fish culture farming D$452,000 Wastewater-based integrated water-mimosa and duckweed farming D$680,000 Wastewater-based integrated water-mimosa and fish culture farming D$830,000 Wastewater-based fish fingerling production D$766,400 Wastewater-based tilapia fingerling production D$920,000

• Mammals, birds, invertebrates, …

• Ecologists versus engineers

• Ecological value depending on:

• Size

• Structural diversity

• Influent quality

• Western Treatment Plant,Melbourne ~ RAMSAR

Benefit 3 - Habitat function

WWTP Liedekerke (Belgium), Aquafin Ltd70,000 PE - 1.3 ha FWS wetland

Benefit 3 - Habitat function

712,834 birds spotted (2 yr)132 species, 39 families29 Red List species

• Education• Recreation (walking, fishing), travel cost method• Art (photography)

Benefit 4 - Human use

Granollers, Metropolitan Area Barcelona, Spain• 06/2006 – 01/2007: 18,000 visitors• Travel cost method 60,000 Euro• 72,000 Euro investment, 12,000 Euro py O&M

Reservoir

River

Dam Water

Trans.

Water

Consumer

WW

Collection

Primary Treatmentand/or CW & WSP

RBF

LBF

SAT/ARR

Distribution

IrrigationEH

EH

Natural treatment systems

• Wastewater not too toxic

• Sufficient incident light

• Temperature not too low

• Adequate quantities of nutrients

• Detention time long enough

• Organic loading not too high

• Need for enough space

Prerequisites for natural treatment systems

Part 1 – Waste Stabilization Ponds

O2

Organic matterBacteria

Oxygen depleted rivers

CO2

Introduction: what is stabilization?

O2

Organic matterBacteria

Oxygen-rich rivers

degradation of organic matter in a confined

and engineered system rather than in

the environment.

• Ponds are simple man-made basins, often surrounded by an earthen embankment.

• In waste stabilisation ponds both aerobicand anaerobic bacteria contribute to waste stabilisation.

• The oxygen required for aerobic stabilisation is produced by photosynthesis, waste stabilisation ponds are therefore typical natural systems: not requiring any electricity for oxygen input.

Principles of ponds

• Very effective removal of pathogens, and therefore effluent suitable for reuse

• Effective BOD removal

• Simple and cheap construction, operation and maintenance

• Low energy requirements

• Simple sludge management

Advantages of WSP

• Large land area required

• Performance strongly affected by temperature

• Potential odour release

• Mosquito proliferation ~ malaria

• Low degree of operational control

Disadvantages of WSP

Anaerobic ponds Facultative pond (s)

and Maturation Ponds

A typical WSP system

Aerated lagoon

Intensification: aerated ponds

Urban WSP

Ho Chi Minh City - Vietnam

NIMBYArea: corruption & illegal housesAmenities

3-5 meter

sludge

Influent

Anaerobic ponds - Mechanisms

The two main mechanisms in Anaerobic ponds:• Sedimentation of particles• Degradation of organic material via anaerobic degradation process

HRT = 1-3 days

Removal efficiencies in APs BOD 40-60% TSS 50-70% Faecal coliforms 90% Helminth eggs 75-90%

Anaerobic ponds - Efficiency

Influent BOD

Sludge layer

Soluble intermediates

Bacteria

CO2, N, P

Algae

O2

Anaerobic degradation

Facultative ponds: Algae – bacteria symbiosis & anaerobic digestion

Typical facultative pond effluent quality:

BOD 20 - 60 mg/l

TSS 30 - 150 mg/l

Faecal coliforms 104-106 1/100ml

Helminth eggs 0-50 1/liter

In most cases additional treatment is required! pathogen removal & algae removal

Facultative ponds - efficiency

• Main objective: pathogen removal

• Entirely aerobic and 1-1.5 m deep

• Typical HRT 3-10 days

• BOD removal less than 25%

• Usually more ponds in series

Maturation ponds

Removal (log units)Bacteria H. eggs

Primary sedimentation 0-1 0-2Activated sludge 0-2 0-2Trickling filter 0-2 0-2Chlorination/ozonation 2-6 0-1WSPs 1-6 1-3

Typical maturation pond effluent quality:

BOD 10 - 50 mg/l

TSS 20 - 100 mg/l

Faecal coliforms 102-103 1/100ml

Helminth eggs 0 1/liter

Maturation pond effluent satisfies the strictest WHO criteria for effluent reuse in irrigation (< 1000 FC/100 mL).

Maturation ponds - efficiency

• WSP have low O&M requirements• Low does not mean no!

• Main O&M activities:• Cleaning inlet/outlet• Cleaning/maintaining embankments• Prevent scum layers in FP and MP• Desludging anaerobic ponds• Influent/effluent monitoring

Operation and maintenance

WSP costs – price of land

Part 2 – Constructed Treatment Wetlands

Based on water flow characteristics• (free water) surface flow (FWS or SF)• subsurface flow (SSF)

Based on plant species characteristics• floating plants (e.g. Lemna, Nymphaea)• submerged plants (e.g. Elodea)• emergent plants (e.g. Phragmites, Papyrus)

Classification

HelophytesPleustophytes

HydrophytesPleustophytes

Vymazal et al., 1998

Different groups of macrophytes

CONSTRUCTED WETLANDS

Free floating plants

Floating leaved plants

Emergent plants

Submerged plants

Surface flow (FWS)

Sub-surface flow (SSF)

Vertical flow (VF)

Horizontal flow (HF)

Upflow

Downflow

Any combination of the above systems is called a “hybrid” system

Advantages• Low-medium investment cost• Low O&M costs• Simple operation and maintenance – unskilled labour• Little or no energy inputs• Can be integrated into landscaping

Disadvantages• Mosquitoes (in Free Water Surface Systems• Start-up problems• Space requirement• Variable performance possible (~ climate)• Lack of good models for design and operation• LOW PRESTIGE

Advantages and disadvantages of CTW

Advantages and disadvantages of CTWFlorida Everglades Stormwater Treatment Area

Courtesy: Jim Bays

Water flows over soil media and < 50 cm deep. Mostly planted with sedges, reeds, rushes. This is a land intensive system (5-10 m2 per PE).

Slotted pipe forwastewaterdistribution

Slope 1%

Rhizome network Watertight membrane

Effluent outlet

Emergent plants

Soil, sandor gravel

Type 1: Free-water-surface or surface-flow CTW

Reed ditches, serpentine shape promotes plug flow and avoids dead zones

Type 1: Free-water-surface or surface-flow CTW

pre-settlement

diversion weir

Water flows below a medium of sand, gravel, soil and/or rock. Grasses and trees are commonly used. Amount of land reduced (3-5 m2 per PE).

Slotted pipe for wastewater distribution

Slope 1%Rhizome network

Watertight membrane

Effluent outlet

Emergent plants

Soil, sand or gravel

Slotted pipe for wastewater distribution

Slope 1%Rhizome network

Watertight membrane

Effluent outlet

Emergent plants

Soil, sand or gravel

Type 2: Horizontal-subsurface flow or rootzone CTW

Water is pumped on the surface and then drains down through the filter layer. Amount of land minimal (2-3 m2 per PE).

Type 3: Vertical-flow or infiltration CTW

Several vertical riser pipes ensure good distribution.

Filter material coarse sand or fine gravel.

Two-step constructed wetland consisting of a HSSF and VSSF flow bed.

Different conditions in both wetlands trigger different removal pathways hybrid systems are usually more efficient.

Type 4: Hybrid CTW

1. Normal CW Physical transfer Plant root oxygen release

HSSF-CW: 1 – 6 g O2/(m2.day)≅ 10 - 60% of daily cBOD

2. Intensified CW Intermittent feeding Passive aeration Tidal flow Active aeration

SSF-CW: <0.1 kW.h/m3

Intens-CW: 0.17 kW.h/m3

Act. Sludge: 0.76 kW.h/m3

O2

O2

Type 5: Intensified wetlands

IW: up to 100 g O2/(m2.day)

44

Forced Bed AerationTM

(picture Scott Wallace, NAWE)

Tidal flow CW

Type 5: Intensified wetlands

landfill leachate (sludge stabilization)

sewage

domestic

municipal separate

combined

agricultural

dairycattle

swinepoultry

industrial

mine drainage coal, metal

food processingwinery, abattoir, fish, potato, vegetable, meat, cheese, sugar , milk productions

heavy industry oil refineries, fertilizers, explosives, polymers, chemicals, pulp and paper mills

runoff urban highway field crop nursery greenhouseairport

Sludge treatment

Rudkøbing

Sludge treatment

32

SLUDGE RESIDUE

1% DM 40% DM

‘natural’, low-tech systems require low but nevertheless adequate maintenance

Vymazal (1998) recommends checking larger systems (> 500 PE) on a daily basis, including:

• pretreatment units• inlet structures• outlet structures

If maintenance ignored:• uneven flow distribution• local overloading• deterioration of treatment efficiency in the long term

Basic maintenance

Lack of maintenance results in failure

Excessive sludge accumulation threatens to block the influent distribution pipes.

50

• autarctic houseboat• 2 vertical-flow CW floating alongside• closed water cycle by means of Reverse Osmosis and UV disinfection• 60,000 Euro (excl. VAT)

GEWOONBOOT, NL

Part 3 – Soil-based systems

• ARR = Aquifer Recharge and Recovery(injection well or infiltration basin recovery well) - ASR = Aquifer Storage and Recovery- ASTR = Aquifer Storage Transfer and Recovery

• BF = Bank Filtration- River bank filtration (RBF)- Lake bank filtration (LBF)

Natural drinking water treatment systems

Soil Aquifer Treatment (SAT)

SAT – Dan region project Israel – 140 .106 m3/year

• Natural and Sustainable Treatment• A Multi-Objective (≈Contaminant) Process• Removal of Turbidity and Suspended Solids• Removal of Biodegradable Organics

• Bulk Organic Matter• Trace Organic Compounds

• Removal of Microorganisms• Removal of Nitrogen (Ammonia + Nitrate)• Replaces or Supports Other Treatment Process

• A Robust Barrier within a Multi-Barrier System• Low Cost

Advantages of RBF/LBF and SAT/ARR

• Only Limited Barrier for Certain Contaminants• Same is true for Granular Activated Carbon, Advanced

Oxidation and Membranes• Proven Barrier for Microbes

• No Reliable Transfer of Experiences to Other Locations• Need for Pilot and/or Demonstration Scale Testing• Soil Column Experiments Scale-Up?

• Possible Release of Fe and/or Mn at Some Sites• Need for subsequent oxidation (post-treatment)• Also, Possible Release of Arsenic (As) and Fluoride (F-)

Limitations of RBF/LBF and SAT/ARR

Part 4 – Ecohydrology / Ecohydraulics

Onsite treatment and reuse

Off-site treatment, (storage) and reuse

In-stream and riparian technologies

Saturated zone

Unsaturated zone

Where does it fit in the water chain?

Quantitative scarcityQualitative scarcity

Vegetated buffers

watercourse & wetland

Buffer strip(natural or man-made)

Source: Jontos (2004)

Vegetated buffer functions

1. Sediment removal (filtration)

2. Nutrient removal (plant uptake & soil adsorption)

3. Stormwater runoff (filtration & infiltration)

4. Water temperature moderation

5. Habitat and wildlife diversity / corridor function

6. Biomass production

Source: Jontos (2004)

Buffer size

Width of VBS range between 2 - 500 meters

Majority fall within 4.6 – 15 meters

Slope of buffer >10%, increase in width

Area ratio range 15:1 to 5:1 or less

watercourseV.B.S

Drainage area

Source: Jontos (2004)

Effects of plants in buffer strips

Function Grass Shrubs Trees

Sediment Trapping High Medium Low

Filtration of Sediment Borne Nutrients, Microbes & Pesticides

High Low Low

Soluble Nutrients & Pesticides Removal Medium Low Medium

Flood Conveyance High Low LowReduce StreambankErosion Medium High High

Source: Jontos (2004)

In-stream remediation – floating wetlands

• Layers of recycled plastic “matrix” bonded together with adhesive foam

• Planted with sod, garden plants, or wetland plants • Plants grow naturally with roots growing through matrix

into the water• Natural eco-system evolves over time Source:

Biohaven

In-stream remediation – floating wetlands

Source: Biohaven

Functions of floating islands

Remove pollutants (nutrients) from water

Provide critical riparian edge, shelter & general wildlife habitat

Erosion control & wave mitigation

Structural alternatives for docks, walkways, bridges & more

Beautify a waterscape

Hyporheic zone treatment (1)

Hyporheic zone treatment (2)

SWITCH demo city - Lodz

SWITCH demo city - Lodz

Lodz – Project 1 – resurfacing Sokolowska river

• Stormwater management improved water quality• Increase water retentiveness less flooding• Improvement of quality of life housing prices

Lodz - Project 2 - Ner river sewage system management

• Green belt• Phytoremediation• Energy

Fish passage

Controlled flooding area – “Room for the river”

La Cienaga de la Virgen, Cartagena, Colombia

The End