Mastertitelformat bearbeiten 2.6.1_ BORDA-DEWATS... · solids, removal of algea retaining of living and dead algea removal of sludge Complete Wastewater Treatment with DEWATS Sedimentation

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Bremen Overseas Research and Development Association www.borda-net.org

DEWATS Training Material

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Bremen Overseas Research and Development Association

DEWATS Training Material.

This training material contains the most important issues for planning decentralised wastewater treatment plants in developing countries. It is based on the book:

“DEWATS – Decentralised Wastewater Treatment in Developing Countries”.

Its philosophy might be described with the slogans on the next page.

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Learnings

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DEWATS Learnings.

Wastewater is treated by applied science, not by propaganda

What will not be maintained, does not need to be built

Only freaks like to handle wastewater

Dissemination of DEWATS is different from selling proprietary articles like cell phones

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DEWATS

Decentralised Wastewater Treatment Systems

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DEWATS Intro.

DEWATS includes only such systems

which are considered suitable

for decentralised application and dissemination in

the case that

qualified maintenance and operation

cannot be expected

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DEWATS Intro.

There are certain measures at hand to discharge effluent of acceptable quality

¬  provision of sufficient space at the source of pollution

¬  pre-treatment at source and post treatment where sufficient land is available

¬  pre-treatment at source and post treatment in cooperation with others

¬  accepting an effluent with higher pollution load

¬  restricting wastewater producing activities at this particular site

¬  connection to a central treatment plant via sewage line

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Fully centralised system ¬  Lowest construction cost per volume of wastewater ¬  Up to five times the cost for the required sewerage ¬  Management costs are comparatively low ¬  Maintenance costs are quite high

Semi-centralised system ¬  Construction costs are relatively low ¬  Costly management may be needed for each plant

Fully decentralised system ¬  Requires capable natural environment for discharge ¬  Structural costs are likely to be the lowest ¬  Requires sludge disposal at site, or costly transportation ¬  Maintenance and management costs are negligible ¬  Centralised service and supervision may be required

DEWATS Intro.

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Philosophy

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DEWATS Philosophy.

DEWATS is based on reliability, longevity, tolerance towards inflow fluctuation, and no need for sophisticated control and maintenance.

DEWATS work without technical energy, and thus cannot be switched off intentionally.

DEWATS provides treatment for wastewater flows from 1 – 1000 m³ per day, from both domestic and industrial sources.

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Why Wastewater Treatment?

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DEWATS Why Wastewater Treatment?

What are the benefits of wastewater treatment?

What kind of wastewater can be treated?

Which problems can be solved by treating wastewater?

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Treatment

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DEWATS Treatment.

„Treatment” means

¬  stabilisation of pollutants via oxidation

¬  removal of solids

¬  removal of harmful substances (N,P, toxins)

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DEWATS Treatment.

Stabilisation is a matter of degradation of organic compounds; it is predominantly a matter of oxidising

¬  carbon (C) to carbon dioxide (CO2),

¬  nitrogen (N) to nitrate (NO3),

¬  phosphorus (P) to phosphate (PO4)

¬  sulphur (S) to sulphate (SO4).

¬  hydrogen (H) to water (H2O).

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DEWATS Treatment.

C6H12O6 + 6O2 CO2 + 6H2O chemical and bio-chemical degradation with or without bacteria

C6H12O6 + 4NO3 6CO2 + 6H2O + 2N2

C6H12O6 3CH4 + 3CO2

bio-chemical degradation through bacteria

no additional oxygen; substances are split by bacteria into compounds, compounds are re-aranged

anoxic respiration

aerobic respiration

Aerobic, anoxic and anaerobic decomposition

bio-chemical degradation through bacteria

anaerobic fermentation

oxygen comes from other substances within the wastewater (here NO3)

free oxygen comes from outside the wastewater

O2

O

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DEWATS Ingredients of life.

Biological wastewater treatment happens through bacteria.

Wastewater is the feed of bacteria.

The bodies of bacteria consist of H, C, O, N, S, P and trace elements.

Bacteria can only multiply as far as those substances are present in wastewater.

H

O

C

N

Ptrace elements

S

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DEWATS Ingredients of life.

Proteins contain all the necessary elements. A favourable proportion between C, N, P and S (varying around a range of 50: 4: 1: 1).

Carbohydrates and fats are composed of C, O and H and cannot be fermented in pure form.

H

O

C

N

Ptrace elements

S

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DEWATS Treatment.

Principle of the anaerobic process

Organic matter + watercarbohydrate proteins lipids

hydrolysing Bacteria

fatty acids

acetogenic bacteria

acetate hydrogen carbohydrate

metanogenic bacteria

methane + carbon dioxide methane + water

water + mineralised sludge + bacteria mass Karstens / Berthe-Corti

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organic matter + oxygencarbohydrates proteins

oxidation of carbon enzymes

citric acid cycle dehydration / hydration

respiration of carbon

enzymes

splitting

water + mineralised sludge + bacteria mass

DEWATS Treatment.

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DEWATS Treatment.

„easily degradable“ enzymes for decomposition are immediately available

„difficult degradable” enzymes have first to be produced by bacteria.

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DEWATS Treatment.

Aerobic is fast. Anaerobic is slow.

The bacterial population, which is responsible for easy degradation tends to predominate over the others.

To protect the "weaker" (slower) bacteria one may separate different bacterial populations in phases.

In case of DEWATS, it is easiest to provide longer retention times so that the "slow" bacteria find their food after the "quick" bacteria have consumed theirs.

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DEWATS Treatment.

Anaerobic treatment of wastewater from: City sewage

Distilleries

Breweries

Canneries

Yeast production

Coffee processing

Milk processing

Food processing

Starch production

Sugar factories

Organic chemicals production

Slaughter houses

Animal and human excreta

Paper mills

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DEWATS Treatment.

from outside or other

substances

to other substances that attract

oxygeninto

atmosphere

Nitrification

aerobic or anoxic conditions

anaerobic conditions become anoxic

Denitrification

+ O = NO3

NO3 - O = N2

Npresent in

different forms

ammonia nitrogen

NH3and / or

nitrate nitrogenorganic nitrogen

kjeldahl nitrogen

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DEWATS Treatment.

Phosphorous compounds remain potential phosphate suppliers.

Phosphorus is removed with the bacteria mass in form of settled sludge.

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DEWATS Treatment.

removal of easily settleable solids

removal of sludge

removal of easily degradable organic

solids

mineralisation of suspended or

dissolved organic compounds,

biogas production

settling of mineralised

particles, collection and ventilation of

biogas

removal of sludge

removal of easily and more difficult

degradable solids

mineralisation of suspended or

dissolved organic compounds

settling of mineralised

particles

removal of sludge

removal of suspended digested

solids and active bacteria mass

settling of finest suspended

solids, removal of algea

retaining of living and

dead algea

removal of sludge

Complete Wastewater Treatment with DEWATS

Sedimentation

begin of anaerobic fermentation of bottom sludge possible

Other treatment steps, such as the removal of toxic materials, stripping of ammonium, etc., are not part of the DEWATS concept.

Post treatment

Anaerobic digestion

Aerobic and facultative decomposition

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DEWATS Treatment Systems.

sedimentation pond biogas digester

Sedimentationseptic tank

Anaerobic digestion

Aerobic and facultative

decomposition

Post treatmentaerobic-facultative ponds and aerobic polishing ponds

Other systems such as UASB, sequencing batch reactors, rotating discs, activated sludge reactors, etc. do currently not belong to DEWATS

Wastewater Treatment Systems (DEWATS)

anaerobic filter anaerobic baffled reactor

planted gravel filter

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DEWATS Treatment.

Area requirements of treatment plants:

septic tank, Imhoff tank: 0,5 m²/m³ daily flow

anaerobic filter: 1 m²/m³ daily flow

baffled septic tank: 1 m²/m³ daily flow

constructed wetland: 30 m²/m³ daily flow

anaerobic ponds: 4 m²/m³ daily flow

facultative aerobic ponds: 25 m²/m³ daily flow

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Bremen Overseas Research and Development Association DEWATS Treatment.

Combined system: UASB (foreground), settler (centre), sediment sludge biogas digester and sludge storage tank (background) (Thailand, Uni Chiang Mei, GTZ)

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Anaerobic Biogas Digesters at Fushan Farm. The pond receives digested sludge for feed of fish. (Zhejiang Province, P.R. China, HRIEE)

DEWATS Treatment.

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Imhoff tank followed by planted gravel filter and polishing pond (Auroville, Tamil Nadu, India, CSR)

DEWATS Treatment.

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Space is often a problem in industrial estates. (Noida, Uttar Pradesh, India, SIITRAT)

DEWATS Treatment.

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Coarse and fine screens should be avoided whenever feasible

Screening is unavoidable in case of poultry wastewater

DEWATS Treatment.

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Ecology

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Even this little stream should stay clean

DEWATS Ecology.

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DEWATS Ecology.

The biological self-purification effect of surface waters depends on:

¬ climate (temperature) and

¬ relative pollution load.

The presence of free oxygen is a precondition for the self-purification process.

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DEWATS Ecology.

Oxygen intake via surface contact

0,6

0,8

1

1,2

1,4

1,6

1,8

5 10 15 20 25 30

temperature in °C

fact

or

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DEWATS Ecology.

Ability of surface waters to recover oxygen after pollution

0

0,1

0,2

0,3

0,4

0,5

0,6

1 2 3 4 5 6

fakt

or k

R

after Garg

cascadesfast river

slow river medium fast river

lake pond

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DEWATS Ecology.

Nutrients from wastewater increase algae growth in receiving waters.

Too many algae turn the water dark and green. Thus, algae do not produce, but consume oxygen.

Supply of free oxygen decreases. Aquatic life is affected.

Nutrients should return to the nutrient cycle: irrigation of agricultural production, gardening.

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DEWATS Ecology.

Chlorine disinfects wastewater.

Chlorine does also disinfect the receiving waters.

Disinfected water is dead water.

Therefore: save chlorine!

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Effluent from paper mills is one of the most polluting and difficult wastewaters (P.R. China)

DEWATS Ecology.

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Parameters

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DEWATS Parameters.

Data required to design DEWATS ¬  daily wastewater flow ¬  times or periods of major wastewater flow or

other data describing fluctuations and maximum flow

¬  average COD values and range of fluctuation ¬  average BOD values or average COD/BOD ratio ¬  suspended solids content, percentage of

settleable solids ¬  pH ¬  ambient temperature and temperature of

wastewater at source

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DEWATS Parameters.

Total solids in wastewater

Water 95%volatile (organic) solids 4%inorganic solids (ash) 1%

Total solids in wastewater

water

volatile (organic) solids

inorganic solids (ash)

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DEWATS Parameters.

Hydraulic load (weak wastewater)

m³/m³ * d wastewater volume per reactor volume per day

m³/m² * d wastewater volume per surface area per day

Organic load (strong wastewater)

kg/m³ * d organic mass (BOD, COD) per reactor volume per day

kg/m² * d organic mass (BOD, COD) per surface area per day

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The Oxygen Demand …is the unit that measures the weight of oxygen which is required to stabilise polluting matter. It is mostly measured in mg/l

COD

BOD

BOD5

total oxygen demand

BOD5 - part of the BOD that can be captured by a defined biological analysing method within 5 days.

BOD - total oxygen demand of biodegradable substances

DEWATS Parameters.

COD - oxygen demand that can be captured by a defined chemical

analysing method

total oxygen demand

if all matter is biodegradable: à BOD = COD

if all matter is biodegradable within 5 days: à BOD5 = BOD

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Treatment Systems

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typical values aerobic ponds

maturation ponds

water hyacinth ponds

anaerobic ponds

anaerobic filters

baffled reactors

loading rates (BOD5 kg/m³*day) 0,11 0,01 0,07 0,3 - 1,2 4,00 6,00efficiency (BOD5 removed) 85% 70% 85% 70% 85% 85%temperature optimum 20°C 20°C 20°C 30°C 30°C 30°C

different sources

Organic loading rates, treatment efficiency and optimum temperature of various treatment systems

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settl. solids susp. solids diss. solidsBOD 100 50 150org. DM 150 50 250min DM 100 25 375

Composition of domestic wastewater

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

BOD org. DM min DM

diss. solidssusp. solidssettl. solids

organic dry matter mineral dry matter

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SS TS BSB CSB0 0 0 0 0

0,25 61% 32% 15% 10%0,5 85% 45% 19% 12%

0,75 90% 57% 21% 15%1 95% 63% 23% 16%

1,5 98% 69% 26% 17%2 100% 73% 28% 20%3 100% 77% 32% 23%4 100% 80% 35% 25%5 100% 80% 36% 28%6 100% 80% 36% 30%7 100% 80% 36% 30%

Removal rates in settling tests of domestic wastewater

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0,2

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0,6

0,8

1

1,2

0 1 2 3 4 5 6 7 8

settling time in hours

% o

f tot

al

SSTSBSBCSB

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Principle of the Septic Tank 1. Sedimentation and floatation 2. Fermentation of bottom sludge

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Characteristics of the Septic Tank

kind of treatment: sedimentation, sludge stabilisation, CODrem 20 - 50%

type of wastewater: domestic and others with settleable solids

advantages: simple, durable, underground, area required: 0,5m²/m³ wwpd

disadvantages: only pre-treatment, effluent not odourless

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hours COD rem. factor0 0%1 27%3 40%

30 55%40 55%

COD removal rates in settlers

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10%

20%

30%

40%

50%

60%

0 10 20 30 40

settling time in hours

CO

D re

mov

al ra

te

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months sludge0 100%36 50%120 33%

Reduction of sludge volume during storage

0%

25%

50%

75%

100%

0 20 40 60 80 100 120

months

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Principle of the Imhoff-Tank 1. Sedimentation 2. Protection against upflow of sludge particles 3. Fermentation of bottom sludge

cross section longitudinal section manhole

inflow outflow Floatation outside funnel Sedimen- tation inside funnel

Imhoff Tank

Cross Section Longitudinal Section

liquid

flow tank scum

sludge

1

2

3

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Imhoff-Tank before placing the cover (Auroville, Tamil Nadu, India, CSR)


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Characteristics of the Imhoff-Tank

kind of treatment: sedimentation, sludge stabilisation, CODrem 20 - 50%

type of wastewater: domestic and others with settleable solids

advantages: simple, durable, underground, odourless effluent, area required: 0,5m²/m³ wwpd

disadvantages: less simple than septic tank, needs very regular desludging

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Principle of the Anaerobic Baffled Reactor 1. Sedimentation/floatation of solids 2. Anaerobic digestion of suspended & dissolved solids through contact with sludge 3. Anaerobic digestion (fermentation) of bottom sludge 4. Sedimentation of mineralised (stabilised) bottom sludge

manholes inflow

outflow

biogas

sedimentation

primary sludge

scum

clarification

inoculation of wastewater with active sludge

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Characteristics of the Anaerobic Baffled Reactor kind of anaerobic degradation of suspended treatment: and dissolved solids, CODrem 60 - 90%

type of pre-settled domestic & strong industrial wastewater: wastewater of narrow COD/BOD ratio

advantages: simple, reliable and durable, high efficiency, underground, area required: 1 m²/m³ wwpd

disadvantages: larger space during construction, less efficient with weak wastewater, longer time for maturation

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HRT(h) BODrem0 0%5 51%

10 82%25 100%30 100%

COD removal rate in relation to HRT in Baffled Reactors

0%

20%

40%

60%

80%

100%

120%

0 5 10 15 20 25 30

HRT in hours

fact

or

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0 0% 0%0,42 82% 1%0,84 94% 2%1,04 100% 3%

10 100% 75%20 100% 94%30 100% 100%35 100% 100%

Comparing Efficency of Baffled Reactor and fully Mixed Reactor

0%

20%

40%

60%

80%

100%

0 5 10 15 20 25 30

HRT in days

fact

or

baffledfully mixed

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1 0,402 0,703 0,908 1,2

Influence of number of up-flow chambers on COD removal in Baffled Reactors

0,40

0,60

0,80

1,00

1,20

1 2 3 4 5 6 7 8

number of chambers

fact

or


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strengths0 0,4

150 0,77300 0,87500 0,95

1000 1,052000 1,13000 1,15

Influence of wastewater strength on treatment efficiency in anaerobic Baffled Reactors

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0,6

0,8

1

1,2

0 500 1000 1500 2000 2500 3000

BOD mg/l

fact

or

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Principle of the Anaerobic Filter 1. Sedimentation/floatation of solids 2. Anaerobic digestion of suspended and dissolved matter inside the filter 3. Anaerobic digestion (fermentation) of bottom sludge

gas manhole

inflow

outflow

sedimentation tank filter units

sludge

scum

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Bremen Overseas Research and Development Association DEWATS Treatment Systems.

Anaerobic filter under construction (Chengdu, Sichuan, P.R.China, CEEIC)

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Anaerobic filter constructed underground (Chengdu, Sichuan, P.R.China, CEEIC)


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Characteristics of the Anaerobic Filter kind of anaerobic degradation of suspended treatment: and dissolved solids, CODrem 65 - 85%

type of pre-settled domestic and industrial wastewater: wastewater of narrow COD/BOD ratio

advantages: simple and durable if well constructed, high treatment efficiency, underground, area required: 1 m²/m³ wwpd

disadvantages: costly in construction because of filter material, clogging possible, effluent smells slightly

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Temeprature °CCOD removal rate10 0,4720 0,8625 1,0030 1,0835 1,10

Influence of temperature on COD removal in Anaerobic Filters

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0,60

0,80

1,00

1,20

10 15 20 25 30 35

temperature in °C

fact

or

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m²/m³ % COD removal0 0 1,06

50 77% 1,06100 94% 1,06200 100% 1,06250 100% 1,06

1,000

COD removal in relation to filter surface in Anaerobic Filters

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0,2

0,4

0,6

0,8

1

0 50 100 150 200 250

specific filter surface m²/m³

fact

or

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Corrugated plastic sheets Rock / Gravel Plastic „bottle cleaners“ or „soft filling“

Filter Material for Anaerobic Baffled Reactor

Loose plastic rings Cinder Bamboo rings


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plants keep filter surface porous

flooded with wastewaterfine sand

coarse sand

coarse gravelventilated channel

O2O2

O2O2

O2

O2O2

O2

O2

waste water

Principle of the Vertical Filter 1. submerged for equal distribution of wastewater through flush charging 2. oxygen follows the percolating wastewater by vacum effect 3. oxygen is available for decomposition during resting time plants keep filter surface porous

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Vertical filter: 1. bed charged by flooding, 2. bed at rest (D. Esser)


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There is never equal distribution without flooding (D. Esser)


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Principle of the Horizontal Filter 1. continuous oxygen supply to the upper layers only 2. anaerob-facultative conditions in the lower layers 3. roots of plants provide favourable environment for bacteria diversity

O2O2O2O2

inflow upper sand layer

internal water level manhole

central outlet shaft

final outlet

perforated pipe connected to swivel pipe for adjustable height

cross collection trench filled with rocks

main filter body filled with coarse gravel cross distribution trench filled with rocks

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Horizontal filter and polishing pond for a bungalow (Auroville, Tamil Nadu, India, CSR)


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Characteristics of the Horizontal Gravel Filter kind of aerobic-facultative-anaerobic degradation treatment: of dissolved and fine suspended solids,

CODrem 60 - 95%

type of suitable for pre-treated domestic and wastewater: weak industrial wastewater

advantages: high treatment efficiency when properly designed and constructed, pleasant landscaping possible, no wastewater above ground, no nuisance of odour

disadvantages: large permanent space, costly, difficult construction, experienced supervision required in the beginning, area required: 30m²/m³ wwpd

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cross sectional area of filter bed [m²]

flow rate [m³/sec]

hydraulic conductivity [m/sec] x slope [m height/m length]

QsAc =

kf * dH / ds Darcy's Law

=

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Influence of Grain Size and Grain Shape on Filter Properties

Ø 5 mm pore space 45,7 % max pore size 0,6 mm spec. Surface 652 m²/m³

Ø 25 mm pore space 22,1 % max pore size 2,8 mm spec. surface 143 m²/m³

Ø 5 mm (5%) and Ø 25 mm (95%) pore space 23,9 % max pore size 1,6 mm spec. Surface 164 m²/m³

mixed grain size mixed grain shape pore space and pore size unpredictable

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remBOD HRT factor60% 0,4570% 0,5375% 0,6180% 0,785% 0,8390% 1,0195% 1,31

Relation between treatment efficiency and HRT in Planted Gravel Filters

0,4

0,6

0,8

1

1,2

1,4

60% 65% 70% 75% 80% 85% 90% 95%

treatment efficiency (BOD rem. rate)

fact

or


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temp HRT (90% rem. Effic)10 8215 4420 2425 1330 735 4

Influence of temperature on HRT in Planted Gravel Filters

0102030405060708090

10 15 20 25 30 35

temperature in °C

HR

T in

day

s


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Principle of Treatment Ponds

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Aerobic-facultative pond at a rice mill (SIITRAT, Delhi)

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Characteristics of the Anaerobic Pond kind of sedimentation, anaerobic degradation, treatment: sludge stabilisation, CODrem 50 - 70%

type of strong and medium wastewater: industrial wastewater

advantages: simple in construction, flexible degree of treatment, little maintenance

disadvantages: occupies open land, can be stinky, difficult mosquito control, area required: 4m²/m³ wwpd

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Characteristics of Aerobic Pond kind of aerobic-facultative degradation, treatment: pathogen reduction, CODrem 60 - 95%

type of weak, pre-treated domestic and wastewater: industrial wastewater

advantages: simple in construction, reliable if properly designed, high pathogen removal rate, fish farming possible

disadvantages: large permanent space requirement, mosquitoes and odour can become a nuisance if undersized, algae can increase effluent BOD, area required: 25m²/m³ wwpd

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temp BOD g/m*d10 7,5

17,5 1430 37

Max. organic load in relation to temperature in Aerobic-Facultative Ponds

0

5

10

15

20

25

30

35

40

10 15 20 25 30

temperature in °C

BO

D g

/m²*

d


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Long canals covered with water cabbage for final treatment of effluent (Fushan Farm, Zhejiang Province, P.R. China, HRIEE)

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charging of sludge

splash plate 30 cm free boardfor sludge15 cm sand

30 cm gravel

rocks

drain

Principle of Sludge Drying Bed


Principle of Sludge Drying Bed

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Sludge truck in Yuhang (Zhejiang Province, P.R. China, HRIEE)

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Biogas Utilisation

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DEWATS Biogas Utilisation.

Biogas Potential of Wastewater theoretical constant

350 l methane per 1 kg BODremoved practical use

200 l biogas per 1 kg CODremoved

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0 0%5 40%

10 75%15 90%20 95%25 98%30 100%35 100%

COD removal rates in relation to HRT in fully mixed digesters

0%20%40%60%80%

100%120%

0 5 10 15 20 25 30 35HRT in days

fact

or


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Principle of Fixed Dome Biogas Plant

1.A) Original charging B) In operation after all gas had been used 2. In Operation, gas storage completely full, highest gas pressure

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Profit on additional cost for biogas use at 80% COD removal rate

-250

-125

0

125

250

500 750 1.000 1.250 1.500

inflow COD mg/l

annu

al p

rofit

annu

al p

rofit

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Bremen Overseas Research and Development Association DEWATS Biogas Utilisation.

Spherical dome digester under construction (Tanzania, CAMARTEC)

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Bremen Overseas Research and Development Association DEWATS Biogas Utilisation.

Anaerobic filter for biogas production of tofu effluent (Zhejiang Province, P.R. China, HRIEE)

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Dissemination

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First recognise the problem, then think of possible solutions

Wastewater treatment may be only a part of a whole package of measures required in a given situation

DEWATS Dissemination.

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There are certain measures at hand to discharge effluent of acceptable quality:

¬  provision of sufficient space at the source of pollution ¬  pre-treatment at source and post treatment where

sufficient land is available ¬  pre-treatment at source and post treatment in co-

operation with others ¬  accepting an effluent with higher pollution load ¬  restricting wastewater producing activities at this

particular site ¬  connection to a central treatment plant via sewage

line.


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A dissemination strategy has to observe:

¬  the social aspect

¬  the economic aspect

¬  the technical aspect

¬  the legal aspect

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Local adaptation of DEWATS is influenced by:

¬  the technical requirements and solutions

¬  the geographical or physical environment

¬  the social and socio-economic circumstances

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Bremen Overseas Research and Development Association DEWATS Dissemination.

The best maintenance could not make good for an originally faulty construction

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Treatment cost are influenced by: ¬  the degree and the kind of water pollution

¬  the degree and kind of treatment

¬  the chosen treatment system

¬  the applied level of technology

¬  the degree of reusing water, sludge and biogas

¬  the management system

¬  the legal discharge standard and fees

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The objectives of organising people may be manifold: ¬  collecting investment capital,

¬  contributing land,

¬  giving permission for trespassing of sewers

¬  collective operation and maintenance

¬  collective financing of services for operation

¬  reuse of effluent or biogas.

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Concepts, which require the participation of the

general public,

are not likely to work too well,

and consequently,

should be avoided whenever possible,

unless a demand responsive approach is adopted.

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Mastertitelformat bearbeiten 2.6.1_ BORDA-DEWATS... · solids, removal of algea retaining of living and dead algea removal of sludge Complete Wastewater Treatment with DEWATS Sedimentation