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Wastes and Wastewater Treatment


Composting toilet. commercial off-the-shelf units and owner-built systems, ... CONTINUOUS COMPOSTING TOILETS. These consist of a single container in which excrement ... – PowerPoint PPT presentation

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Title: Wastes and Wastewater Treatment

Wastes and Wastewater Treatment
  • High and Low Technologies

Wastewater Treatment Types
  • Small Scale
  • Large Scale
  • Remote Rural
  • Metropolitan City
  • None
  • Primary Secondary Tertiary
  • Conventional
  • Emerging
  • Developing Novel

Source J. Radcliffe, 2004
Wastewater Treatment
  • Conventional treatment of sewage or wastewater
    involves a series of physical,
  • chemical and/or biological processes to remove
    solids, organic matter, pathogens,
  • metals and nutrients.
  • Preliminary physical screening of influent to
    remove coarse particles
  • such as gravel small stones and sand.
  • 2. Primary Treatment removal of the most of the
    remaining particulate matter.
  • Remove 50 suspended solids
  • Reduce BOD
  • Reduce 10 N and P
  • Source J. Radcliffe

Secondary Treatment
3. Secondary aerobic biological processes-
microbially metabolise dissolved and suspended
organic matter. Slow rate processes aerated
lagoons and stabilisation ponds. Fast rate
processes activated sludge technologies. Fixed
bio-film processes trickling filters. Organic
matter provides energy and nutrients for
microbial populations, Organic matter is oxidised
to carbon dioxide, water and other end products.
4. Secondary sedimentation (Clarification) to
remove the biomass produced. The biomass may
then be treated by aerobic or anaerobic
digestion, e.g. by composting. Removes up to
50 nitrogen Converts phosphorus to phosphates.
Removes about 80-95 of the BOD and suspended
solids. Source J. Radcliffe
Examples of air diffusers
Environmental Dynamics Inc.
Facultative lagoons
  • Facultative lagoons are primarily anaerobic
    systems with an aerobic top layer that all but
  • for at least a few hours during the night.
  • Dissolved oxygen virtually disappears after
    photosynthesis ceases .
  • During the winter months the diurnal changes in
    the lagoon are minimal compared to those observed
    during the summer.

Source Linvil G. Rich Department of
Environmental Engineering and Science Clemson
University, USA
Trickle bed filters
  • Trickling filter beds are used where the
    settled sewage liquor is spread
  • onto the surface and of a deep bed made up of
    substrates such as stone,
  • coke limestone chips or fabricated media.
  • The media must have high surface areas to
    support the biofilms.
  • Biological films of bacteria, protozoa and fungi
    form on the
  • medias surfaces and metobolize organic content

Rotating Biological Contactors
  • Consist of large diameter corrugated
  • plastic media centred around a horizontal shaft,
  • mounted in a steel or concrete tank.
  • The media is slowly rotated, submerged 40 in
  • the wastewater.
  • Organisms in the wastewater attach and multiply
    on the rotating media until they
  • form a thin layer of biomass.
  • During rotation, the media carries the biomass
    and a film of wastewater into the air
  • where oxygen is absorbed.
  • The dissolved oxygen and organic materials in the
    wastewater diffuse into the
  • biomass and organics are metabolized.
  • Excess biomass shears off at a steady rate as the
    media rotates.
  • These solids are carried through the RBC system
    for subsequent removal in a
  • conventional clarifier.

Source Siemens http//www.usfilter.com/NR/rdonly
Activated Sludge-Step feed activated sludge plant
  • A N/DeN, step feed, activated sludge plant
    configured to achieve some nitrogen removal.
  • The activated sludge plant can consists of four
    reactors, each with two stages consisting of
    anoxic and aerobic zones.
  • Return sludge from the clarifiers is sent to the
    first stage of each reactor.

Biological Nutrient Removal
  • Ludzack Ettinger
  • Two step biological nitrification-
    denitrification process with anoxic zone followed
    by aerobic zone.
  • The anoxic zone has a source of organic material
    from influent wastewater. Denitrifying bacteria
    use oxygen from nitrate to metabolize organic
    matter in wastewater.
  • Aerobic zone nitrification, organic N and NH3
    to nitrate
  • Modified Ludzack Ettinger (MLE)
  • Same process with internal recycling of aerobic
    to anoxic zones at upto to 5 times average flow
    higher denitrification rates.
  • A20 Process has a anaerobic zone before the MLE
    Phosphorus is absorbed by microbes and is removed
    in activated sludge.

Source Hatch Mott MacDonald www.hatchmott.com
Bardenpho process nitrification
denitrification system
  • anaerobic, anoxic and aerobic zones in sequence.
  • Various Systems i.e. 3, 4 and 5 stage systems.
  • Five stage adds a anaerobic zone at front to
    remove P by absorbance to microbes and removal in

Source Hatch Mott MacDonald www.hatchmott.com
Biological Nutrient Removal
Sequencing Batch Reactors Activated sludge,
wastewater Added to single batch reactor
Performs biological treatment And secondary
clarification in a single tank using time
control sequence. Source USEPA
Oxidative Ditch (activated sludge with long
sludge ages) Single reactors Alternating
between oxic and anoxic areas. Small to medium
scale wastewater treatment for removal of
nitrogen. Source Dayton and Knight Ltd
Consulting Engineers, ISBN 0-662-31307-0
Vertical Loop Reactor (VLR) for Biological
  • process is a design based upon looped reactors
    in series that allows DO stratification.
  • simultaneous nitrification/denitrification
  • biological phosphorus removal
  • storm water treatment.
  • are similar to oxidation ditches that have been
    flipped on their sides.
  • upper and lower compartment, separated by a
    horizontal baffle running the length of
  • the tank.
  • Typically, two or more basins make up the VLR
    system, with the first tank
  • operating as an aerated anoxic reactor and
    aerated aerobic reactor.
  • Course Bubble Retention 1-2 mins.

Source Siemens Water Technologies
Tertiary Treatment
  • 5. Chemical Coagulation and Filtration Removal
    of colloidal and suspended solids specific
    metals, pathogens, and nutrients.
  • Activated carbon adsorb hydrophobic organic
  • Lime precipitate various cations and metals at
    high pH.
  • 6. Membranes including micro-filtration and
    reverse osmosis ability to remove very fine
    particles, salt, other minerals, large organic
  • Advanced Wastewater Treatment
  • membrane systems when the effluent is to be
    processed to potable or near potable standard.
  • Coagulation and membrane systems

Dissolved Air Flotation and Filtration (DAFF)
Secondary lagoon effluent
Aluminium sulphate and polymer
Water mixed with air under Pressure 500kpa
Floc formation
Surface sludge to digestor
Fine air bubbles causes flocs to rise to Surface
Water under scum floated water is filtered.
Sand anthracite and gravel
Disinfection e.g. chlorination
Wastewater Treatment
Raw Sewage
Reactor or aerobic tanks Activated Sludge
H2S is collected And treated
Biological floc or sludge
Settling tanks Clarifiers
Large pollution screening
Excess Sludge
Thickened By DAF
Grit Removal
Grit settling Lagoons
Digestors Mixed /Heated 35oC Anaerobic
fats greases
Turbines For power
Preaeration Tanks
Grit discarded
Sludge for soils
Secondary Lagoons
DAFF plant
Sedimentation Tanks
Gravity Thickening Tanks
Membranes Source J. Radcliffe
Appropriate Technology
  • Appropriate to the
  • environmental, cultural and economic conditions,
  • fewer resources- lower cost and less impact on
    the environment.
  • technologies which are suitable for use in
    developing nations or underdeveloped rural areas,
  • lack the money and specialised expertise to
    operate and maintain hogh technology.
  • labour-intensive solutions are usually preferred
    to capital-intensive ones
  • In practice, it is often something that might be
    described as using the simplest and most benign
    level of technology that can effectively achieve
    the intended purpose in a particular location.
  • Sanitation/wastewater treatment
  • Sanitation is the hygienic disposal or recycling
    of waste, as well as the policy and practice of
    protecting health through hygienic measures

Septic Tanks
  • septic tank system is a small scale sewage
    treatment system common in areas with no
    connection to main sewerage pipes.
  • anaerobic bacterial environment develops in the
    tank which decomposes or mineralises the waste
  • 4,000 to 6,500 Litres
  • Wastewater inlet to tank and drainage
    system-soakage or seepage areas
  • Usually two chambers 1) solids settle
    (anaerobically digested) and scum floats 2)
    liquids flow to second chamber, more settling.
  • Liquid drains to seepage areas via piping
    network- stone filled trench multiple drainage
  • Percolate into soils- further purification by
    microbial action, vegetation uptake, to

Low energy toilets-minimum energy, on-site
alternative to centralised reticulated systems
Dry Toilets Pit toilets are not suitable for
areas with high rainfall. They should be located
away from watercourses or bores and the pit
should be above the water table. Generally
cannot dispose of grey water. Access to dry
toilets can be difficult for people with
disabilities because the toilet is elevated
above the compost container and people are
required to climb stairs. Source National
Indigenous Housing http//www.facs.gov.au/indigeno
  • Pit latrine-waste goes directly into a hole in
    the ground.
  • Composting Toilet - waterless toilet (CT).

Pit Toilets/Latrines-Types
  • Cat hole one-time use pit toilet often utilized
    by campers and hikers
  • Advanced Designs larger and covered with a
    supporting structure
  • provision for seating, roof and shelter.
  • Ventilated improved pit latrine (VIP)
  • is a pit toilet with a black pipe fitted to the
    pit, and a screen at the top outlet
  • of the pipe. The smell is carried upwards by the
    chimney effect and flies are
  • prevented from leaving the pit and spreading
  • Long-term pit toilets the reduction in mass of
    waste products by the ongoing
  • process of decomposition allows the pit to be
    used for a long time.
  • Permanent pits used by a great number of
    people built with a concrete lining
  • for permanence is periodically emptied, the
    waste is transported to a sewage
  • treatment facility or composted.
  • Dry pits concrete-lined waste pit may be
    preferred near streams, slopes.

Composting toilet
  • commercial off-the-shelf units and owner-built
  • carbon based material or 'bulking agent', such
    as dry leaves
  • or softwood shavings, should be regularly added,
  • CT needs to be well drained. The liquid run-off
    is often
  • treated in a sealed evapotranspiration trench or
    a solar
  • evaporating tray.
  • Vent pipes provide aeration to the pile

single container in which excrement is
deposited, and decomposes as it moves slowly
through the container. It is then removed as
compost from the end-product chamber.
Source Leonie Crennan, www.yourhome.gov.au
Composting toilet

Batch CTs consist of two or more chambers that
are alternated, one is in use the other is used
to compost without the addition of fresh faeces.

Constructed Wetlands
  • created for discharge of wastewater, stormwater
    runoff or sewage treatment.
  • act as bio-filters removing/reducing sediments,
    inorganic (e.g. heavy metals, N and P)
  • and organic pollutants (e.g. hydrocarbons, BOD).
  • Vegetation in wetlands uptake nutrients (N and
    P), heavy metal uptake-different plant
  • species have different uptake.
  • Vegetation acts as a physical substrate on which
    micro-organisms can grow these
  • and chemical processes are mostly responsible for
    pollutant and waste breakdown.

Constructed Wetlands
  • Types
  • Subsurface Flow (a) horizontal (b) vertical
  • -gravel or sand medium, vegetated
  • 2. Surface Flow marsh/swamp soil, sediment,
    clay vegetation. Phagmites, Cattails (Typha
    spp.), sedges (Carex sp) , and bulrushes are used
  • Bulrushes-family Cyperaceae, typically of the
    genus Scirpus, Bolboschoenus, or Schoenoplectus

Constructed Wetlands
  • Removal of contaminants by physical, chemical,
    and biological processes.
  • Treatment of wastewater occurs as it passes
    through the wetland medium
  • and the plant rhizosphere.
  • Decomposition of organic matter is facilitated by
    aerobic and anaerobic
  • micro-organisms.
  • Microbial nitrification and subsequent
    denitrification releases nitrogen as
  • gas to the atmosphere.
  • Phosphorus is co-precipitated with iron,
    aluminium, and calcium compounds
  • located in the root-bed medium.
  • Suspended solids are filtered out as they settle
    in the water column in
  • surface flow wetlands or are physically filtered
    out by the medium within
  • subsurface flow wetland cells.
  • Harmful bacteria and viruses are reduced by
    filtration, adsorption and
  • predation by micro-organisms in biological

Constructed Wetlands- Nitrogen compounds
  • forms of nitrogen in wetlands include organic
    nitrogen, ammonia, ammonium,
  • nitrate, nitrite, and nitrogen gases.
  • Scarce inorganic forms limit plant growth
  • Ammonia is toxic to fish.
  • NH3 H2O lt-----gt NH4 OH- (aerobic and
    anaerobic conditions, organic decomposition)
  • Ammonium ion (a) can be absorbed by plants/algae
    and converted to organic matter.
  • (b) immobilized to negatively charged soil
  • (c) stable under anaerobic conditions.
  • (d) wetlands surface ammonium ions to nitrite
    and nitrate.
  • Denitrification by bacteria is the biochemical
    reduction of oxidized nitrogen anions,
  • nitrate-N and nitrite-N, with concomitant
    oxidation of organic matter.
  • NO3- ---gt NO2- ---gt N2O ---gt N2
  • Nitrosomonas sp Nitrobacter sp AnO2

Mitsch Gosselink, 1986), wikipedia
Constructed Wetlands- Phosphorus
  • Phosphorus inorganic and organic forms.
  • Biologically available orthophosphates referred
    to as soluble reactive
  • phosphorus (SR-P).
  • Dissolved organic phosphorus and insoluble forms
    of organic and inorganic
  • phosphorus are generally not biologically
  • Phosphorus may be sequestered within a wetland
    system by the following
  • The binding of phosphorus in organic matter as a
    result of incorporation into
  • living biomass, and
  • 2) precipitation of insoluble phosphates with
    ferric iron, calcium, and aluminium found
  • in wetland soils
  • Higher plants uptake during growth and release
    when dead/decaying. Plant
  • harvesting can maintain higher P uptake.
  • Variable P uptake depending on plant specie
    (reports of 5-80)

Sources wikipedia
Constructed Wetlands-plants
  • Plants
  • substrate for bio-film,
  • transport oxygen which is released at the
    bio-film/root interface
  • increase soil or other root-bed medium hydraulic
    conductivity- as roots and
  • rhizomes grow they loosen soil medium and when
    decaying create macropores.

Wastewater flows through a series of tanks where
flora (algae, aquatic plants, marsh plants) and
fauna (worms, snails, crustaceans) break down the
wastes and eliminate nutrients
UNEP - International Environmental Technology
Centre United Nations Environment Programme
Advantages and Disadvantages of Conventional and
Non-conventional Wastewater Treatment

  • Internet Private Commercial Companies
  • WHO
  • United National Environment Program
  • International Water Association
  • Australian Water Association
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