Wastewater

Water and Sanitation

Residential Wastewater
flushing systems with

  • centralized treatment
  • decentralized treatment

dry systems, mainly decentralized managed, like

  • pit latrines
  • dry toilets

Residential Wastewater: Fractions

  • Black Water: Waste water from Toilettes and Urinals
  • Brown Water: Feces, with or without water
  • Yellow Water: Urine from Urinals or Separation toilettes, with or without water
  • Grey Water: Waste water from Kitchen, Bath, Washing etc .

Pathogen distribution across the different streams
Faeces:

  • Contains most of the pathogens
  • Exposure to untreated faeces is considered unsafe

Urine:

  • Low health risk (only a few diseases transmitted through urine)
  • Risk of faecal cross-contamination

Grey Water:

  • Low health risk
  • Contamination through laundry, washing diapers, from foodstuffs
  • Lower risk of faecal cross-contamination

Source: Sandec Training Tool

Decentralized Sanitation

Decentralized/Pit Latrines

  • collect human feces/urine in a hole
  • liquids seep into the ground
    Exception -> fully lined pit latrines

While one pit is in use, the other one is closed.
The system consists of:

  • 2 pits
  • 2 pieces to reinforce the pits
  • 1 concrete slab (movable)
  • 1 toilet house (movable)

Recommendations

  • installation in reasonable distance from house
  • avoidance contact to collected material, emptying the pit regularly
  • faecal sludge management essential
    • transport
    • treatment
    • usage

Decentralized/Urine diversion Toilets/Ecosan

Ecosan Toilets

Building a Ecosan toilet

General information about diversion toilets

Ecosan toilet in Bangalore, India

Stabilization Ponds
Combination of:

  • anaerobic ponds
    • TSS settles
    • dissolved C -> anaerobic digestion
  • facultative Lagoon
    • O2 only at the surface
    • BOD removal -> bacteria -> oxygen from photosynthesis of algae
    • shallow , large surface
      • high sunlight radiation
      • high atmospheric O2 dissolve
    • sediment layer
  • maturation ponds
    • aerobic conditions
    • removal of pathogens/nutrient reduction aerobic bacteria
    • shallow , large surface
      • high sunlight radiation
      • high atmospheric O2 dissolve

Summary Stabilisation Ponds:

  • can be made and repaired with local materials
  • no real problem with odors and flies if designed properly
  • low operating costs
  • no electricity required
  • requires expert design and supervision
  • requires large land area
  • Sludge require secondary treatment and appropriate discharge
  • removal of -> pathogens, worms and helminth eggs
  • not suitable in areas where stringent discharge standards exist -> additional stages of post treatment necessary

WHO (2006). WHO Guidelines for the Safe Use of Wastewater, Excreta and Greywater - Volume IV: Excreta and greywater use in agriculture; R. Schertenleib et al.: Compendium of Sanitation Systems and Technologies, eawag

Constructed Wetland
Pretreatment

  • settling pond ≥1.5 qm/Person
  • multi chamber septic tank ≥ 300l/Person
  • raw wastewater filter ≥ 1.2 qm/Person

Main Treatment

  • vertical reedbed filter ≥ 4 qm/Person
  • horizontal reedbed filter ≤ 100 g COD/cbm*day

Post treatment > 1qm/Person

Source: Arbeitsblatt DWA-A 262, 2017

Decentralized Technical WWT Plants like:

  • Fixed Bed Reactor
  • Moving Bed Reactor
  • Membrane Bioreactor
  • Trickling Filter
  • Sequency Batch Reactor
  • Activated Sludge Reactor
  • Upstream Anaerobic Sludge Bed Reactor
  • Aerated Wetlands

Urine Utilization
Pathogenes

  • Urine:
    • mostly free of pathogens,
    • but risk of cross-contamination through faeces
  • Recommendation before use:
    • Urine storage (in an airtight container)
      • degradation of urea to ammonia leads to
        • pH increase (to around 9)
        • pathogen reduction
  • Further inactivation of pathogens is expected in the field between time of fertilization and consumption
  • Storage also important as the use of the urine as a fertilizer on farmland is only possible during the two short planting seasons per year.

Storage of urine for pathogen reduction

  • Urine collected from individual households and used for the household’s own consumption:
    • suitable for fertilizing all types of crops if one month is allowed between fertilization and consumption

Source: Caroline Schönning: Urine diversion – hygienic risks and microbial guidelines for reuse (for WHO)

Urine application

  • Urine dilution before use:
    1 part of urine to 2-5 parts of water depending on soil fertility and plants
  • Application: the diluted solution is sprinkled around the plants/crops in the root zone for plant uptake
  • Due to high N-concentrations, urine is especially good for crops which normally are very limited by the supply of nitrogen

Sludge treatment

  • Surface disposal: Stockpiling of sludge that cannot and will not be used elsewhere
  • Land application: Depending on the sludge quality, application to public or private lands
    • agriculture
    • landscaping
  • Composting: General definition: Stabilized sludge is also referred to as ‘Biosolids’.
    • Compost: product of controlled aerobic degradation of organics into a soil-like substance
    • Humus: material removed from an alternating pit, produced passively underground
    • Co-Composting: controlled aerobic degradation of organics using more than one feedstock:
      • Faecal sludge: high moisture and nitrogen content
      • Biodegradable solid waste: high in organic carbon and good bulking properties (i.e. it allows air to flow and circulate)
  • Sedimentation / Thickening tanks: Settling ponds that allow the sludge to thicken and dewater. The effluent is removed and treated, while the thickened sludge can be treated with a subsequent technology.
  • Unplanted drying beds:
    • simple, permeable bed with collection of leachate (50% to 80% of the sludge volume drains off as liquid)
    • sludge drying by evaporation, however sludge is not stabilized
  • Planted drying beds:
    • Similar to an unplanted drying bed with increased transpiration
    • Key feature: Fresh sludge can be applied directly onto previous layer; the plants and their root systems maintain the porosity of the filter
  • Anaerobic digester: anaerobic treatment technology that produces:
    • a digested slurry ► soil amendment
    • biogas ► energy

Source: R. Schertenleib et al.: Compendium of Sanitation Systems and Technologies, eawag, http://doc.rero.ch/record/309484/files/12-13._Compendium_2nd_Ed_Lowres_EN.pdf

For more information:

2017 UN World Water Development Report, Wastewater: The Untapped Resource
http://www.unesco.org/new/en/natural-sciences/environment/water/wwap/wwdr/2017-wastewater-the-untapped-resource/

The United Nations World Water Development Report 2019
https://www.unwater.org/publications/world-water-development-report-2019/

https://sswm.info/sites/default/files/reference_attachments/EAWAG%20SANDEC%202008%20Module%204%20Sanitation%20Systems%20and%20Technologies%20-%20Presentation.pdf

https://www.who.int/water_sanitation_health/monitoring/coverage/monitoring-dwater/en/

Water Use

Water Stress:

  • lead to an awareness about water resources and how to provide enough water for use worldwide

Drivers for Water Reuse

  • Need for new/additional water supplies for drinking and other purposes (mainly irrigation)
  • Need to leave high quality water sources for drinking purposes
    • Reclaimed water for other purposes than drinking
  • Reuse of nutrients
  • Amount of reclaimed water is less subject to seasonal fluctuations
  • Costs of drinking water are increasing

Water Sources for Water Reuse e.g.
Wastewater: Wastewater from any kind of residential source
Greywater: Wastewater from kitchen, bath, washing, laundry etc.
Process Water: Industrial process water, e.g. cooling water, wash water

Relevant Parameters for Reuse Purposes
Microbiological:

  • Bacteria
  • Viruses
  • Worms
  • Protozoe

Chemical:

  • Organic parameters (incl. anthropogenic organic trace substances, Nanoparticles (1 – 100 nm))
  • Inorganic parameters (TDS)

Physical-chemical characteristics:

  • pH (alkaline, acid), Temperature
  • Electrical conductivity
  • Oxygen

Sensorial:

  • Color, Odor, Foam
  • Taste
  • Turbidity

Anthropogenic Organic Trace Substances

  • pollution groups -> are mainly made by products of daily use
    e.g. body care products, hormones, fire retardants, plasticisers, pesticides, industrial additives and aids

Barriers for Water Reuse
Risk Barriers:
Contaminants in Recycled Water

  • Medicaments
  • Microplastic
  • Heavy metals
  • Pathogens, Worms
    -> Health Risk
    -> Contamination of soil or groundwater resources

User Barriers
Water Reuse

  • Avoidance/Cultural Reasons
  • risky for User/Consumer if used for:
    • Irrigation
    • Food Production
    • Aquifer Recharge
  • more expensive?

Acceptance
Information -> Awareness
Quality Guarantee -> Sufficient Treatment
Control -> Monitoring

Major applications for water reuse

1. Agricultural use: Crop irrigation, aquaculture
2. Landscape irrigation: Parks, play grounds, etc.
3. Industrial use: Cooling water, process water, dust control, concrete curing, etc.
4. Non-potable urban uses: fire protection, toilet flushing, commercial car washing
5. Groundwater recharge: replenishment, saltwater intrusion control
6. Potable reuse:
indirect: blending with public water supplies (surface water or groundwater)
direct: pipe-to-pipe water supply after treatment

International Standard for Irrigation
ISO 16075 “Guidelines for treated wastewater use for irrigation projects“ in 4 parts:
1) The basis of a reuse project for irrigation
2) Development of the project
3) Components of a reuse project for irrigation
4) Monitoring
-> improved irrigation

Irrigation

  • Subsurface irrigation
  • Surface irrigation
    • flush/flood irrigation, furrows
    • sprinkling irrigation
    • micro irrigation (drip irrigation)

But, no irrigation without drainage!!! Problems with irrigation caused by:
water run off -> soil Erosion
evaporation -> salinization
silting -> clogging
dammed water -> plants cannot grow (except rice)

Furrow Irrigation
parallel channels along the field length

  • in the direction of predominant slope
  • water is applied to the top end of each furrow
  • flows down the field under the influence of gravity
  • distance of furrows -> space depends on crop species

speed of water depends on:

  • soil infiltration rate
  • slope
  • inflow rate
  • design of ground

Aquaculture
Controlled cultivation of aquatic plants or animals or both.
Modified maturation pond

  • Filtration in the roots area
  • Uptake of remaining nutrients from treated wastewater

Aquifer Recharge
Intentional recharge of water (treated surface water or treated waste water) to suitable aquifers for subsequent recovery

Aquifer Recharge Systems for treated wastewater
recharge basin:

  • infiltration pond
  • lagoons

Injection well:

  • into the vadose zone
  • directly into the aquifer

Reuse of Residential Greywater
direct discharge into ponds could be critical
►risk of eutrophication
►bad smell

direct reuse:

  • for irrigation of plants, trees
  • (not recommendable for fruits etc.,
    risk of introducing pathogens)

reuse after treatment for:

  • washing
  • toilet flushing
  • garden watering
  • irrigation

-> depending on water quality

Rain Water

Simple Water Cycling Tips
Bath Water:

  • Harvest rainwater from roofs into a tank
  • Use it for bathing or washing

Irrigation:

  • Use rainwater to grow food

Cooling:

  • Place trees on the east and west sides of a building to cool air instead of using air conditioning
    Source: Brad Lancaster: Rainwater Harvesting, 2014

Precipitation:

  • can occur as rain, hail, sleet and snowfall
  • is the primary source of fresh water
  • is naturally distilled through evaporation prior to cloud formation

Source: Brad Lancaster: Rainwater Harvesting, 2014

Rainwater Harvesting
benefits of rainwater:

  • is soft due to the lack of calcium carbonate or magnesium in solution
  • is excellent for cooking, washing, watering
  • is free of charge

Source: Brad Lancaster: Rainwater Harvesting, 2014

Collection of Rainwater consider:

  • the local rainfall pattern
  • the size of the collection surfaces
  • the surface’s materials and their drainage characteristics
  • sizing and material of piping systems
  • the levels of pollution of the collection surface
  • the risk of contaminating the system

Source: DIN EN 16941-1: 2018

Rainwater Pollution

Runoff from divers dispersed sources:

  • Waste storage
  • Roofs
  • Motor vehicle emissions
  • Cleaners, detergent
  • Animal feces
  • Sediment, pesticides, fertilizer
  • Yards, farms → Nitrogen

Source: Brad Lancaster: Rainwater Harvesting, 2014

Collecting Rainwater
Impact of quality depending on the surfaces:

  • green roof -> coloration
  • bitumen containing material -> coloration, tar
  • cement with fibres -> emission of fibres in the long term
  • copper, lead or zinc roofs -> increased concentrations of heavy metals

Source: DIN EN 16941-1: 2018

Water Conservation Strategies at Home

  • No swimming pools – use community pools
  • Plumbing leaks – repair them
  • Washing machines which use less than 38L per load of wash
  • Rainwater for toilet flushing
  • Reduce water consumption
  • Only natural outdoor misting systems
  • Greywater and Rainwater Use at Home

Source: Brad Lancaster: Rainwater Harvesting, 2014

Treatment of Rainwater
1. removal of coarse particles upstream of the storage
2. retention of fine particles by sedimentation and flotation in the storage device
3. Filtering downstream of the storage device, depending on the intended use
-> Disinfection, deodorization, discoloration may be required additionally
Source: DIN EN 16941-1: 2018

Storage of Rainwater
The storage device shall be protected against…..

  • frost,
  • extreme temperatures
  • direct sunlight,

measure -> e.g. buried underground
The structural behavior shall be taken into account when positioning the storage device.
Source: DIN EN 16941-1: 2018

Distribution of treated Rainwater
The treated rainwater/non-potable water shall be distributed by:

  • pumping from the storage device directly to the point of use
  • pumping from the storage device to an intermediate cistern/tank near the point of use
  • using a gravity cistern
  • using a full gravity system.

Source: DIN EN 16941-1: 2018

Rainwater Harvesting Principles for Lands
1. Begin with long and thoughtful observation.
2. Start at the top of your watershed and work your way down.
3. Start small and simple.
4. Spread and infiltrate the flow of water.
5. Plan for an overflow route, and manage that overflow water as a resource.
6. Maximize living and organic groundcover.
7. Continually reassess your system: the “feedback loop”.
Source: Participatory Ecological Land-Use Management association of east and southern Africa and Mr. Zephania Phiri Mnaseko and other water harvesters. From: Brad Lancaster: Rainwater Harvesting, 2014

Water Conserving Techniques

  • dams
  • terraces
  • waffle gardens
  • grit garden
  • gravel mulched fields
  • cliff base plantings
  • floodwater farming
  • irrigation

Source: Brad Lancaster: Rainwater Harvesting, 2014

For more information:
2017 UN World Water Development Report, Wastewater: The Untapped Resource
http://www.unesco.org/new/en/natural-sciences/environment/water/wwap/wwdr/2017-wastewater-the-untapped-resource/
The United Nations World Water Development Report 2019
https://www.unwater.org/publications/world-water-development-report-2019/

https://sswm.info/sites/default/files/reference_attachments/EAWAG%20SANDEC%202008%20Module%204%20Sanitation%20Systems%20and%20Technologies%20-%20Presentation.pdf

https://www.who.int/water_sanitation_health/monitoring/coverage/monitoring-dwater/en/