Wastes and Wastewater Treatment

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Wastes and Wastewater Treatment

• High and Low Technologies

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Wastewater Treatment Types

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

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Source J. Radcliffe, 2004
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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

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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
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Examples of air diffusers
Environmental Dynamics Inc.
http//www.wastewater.com/images/EDI20Aeration20
Tech.pdf
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Facultative lagoons

• Facultative lagoons are primarily anaerobic
  systems with an aerobic top layer that all but
  disappears
• 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
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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

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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
res/2913EA5A-F27A-4D92-BE46-7055205E81BA/0/ENRBCDS
0207.pdf
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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.

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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
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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
  sludge.

Source Hatch Mott MacDonald www.hatchmott.com
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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
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Vertical Loop Reactor (VLR) for Biological
Treatment

• 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
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Tertiary Treatment

• 5. Chemical Coagulation and Filtration Removal
  of colloidal and suspended solids specific
  metals, pathogens, and nutrients.
• Activated carbon adsorb hydrophobic organic
  compounds
• 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
  molecules.
• Advanced Wastewater Treatment
• membrane systems when the effluent is to be
  processed to potable or near potable standard.
• Coagulation and membrane systems

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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
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Wastewater Treatment
Raw Sewage
Reactor or aerobic tanks Activated Sludge
Effluent
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
Methane
Digestors Mixed /Heated 35oC Anaerobic
fats greases
Turbines For power
supernatant
heat
Preaeration Tanks
Grit discarded
Sludge for soils
Secondary Lagoons
DAFF plant
Sedimentation Tanks
Gravity Thickening Tanks
Discharge
Sludge
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Membranes Source J. Radcliffe
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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

Wikipedia
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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
  holes.
• Percolate into soils- further purification by
  microbial action, vegetation uptake, to
  groundwater.

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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
us/housing_guide2/b3.htm

• Pit latrine-waste goes directly into a hole in
  the ground.
• Composting Toilet - waterless toilet (CT).

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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
  disease.
• 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.

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Composting toilet

• commercial off-the-shelf units and owner-built
  systems,
• 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

CONTINUOUS COMPOSTING TOILETS These consist of a
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
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Composting toilet

BATCH COMPOSTING TOILETS
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.

Sourcehttp//www.greenhouse.gov.au/yourhome/techn
ical/fs27.htm
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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.

COSalisbury
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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
  worldwide.
• Bulrushes-family Cyperaceae, typically of the
  genus Scirpus, Bolboschoenus, or Schoenoplectus

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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
  films.

wikipedia
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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
  particles.
• (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

atmosphere
Mitsch Gosselink, 1986), wikipedia
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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
  available.
• 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
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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
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UNEP - International Environmental Technology
Centre United Nations Environment Programme
Advantages and Disadvantages of Conventional and
Non-conventional Wastewater Treatment
Technologies.

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Information

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