Reuse of Appropriately Treated Domestic Wastewater in Irrigated Agriculture

1
Reuse of Appropriately Treated Domestic
Wastewater in Irrigated Agriculture

• Ralf Otterpohl and Moataz Shalabi
• Institute of Municipal and Indusrial Wastewater
  Management
• Technical University of Hamburg-Harburg

2
Agenda

• Reuse of wastewater in agriculture, why?.
• Technical options for health protection.
• Anaerobic treatment Vs activated sludge and pond
  technologies in Jordan.
• Integrated wastewater treatment in Faisalabad.
• Design of SBR and A stage of AB process for
  wastewater treatment in Haroonabad.
• Rotating Biological Contactors at channel No.4
  Faisalabad.
• Recommendations and conclusions.

3
Wastewater Reuse in Agriculture, Why?

• Typical wastewater effluent from domestic sources
  could supply all of the nitrogen and much of the
  phosphurus and potassium that are normally
  required for agricultural crop production (FAO
  1992).
• A high cost of artificial fertilizers.
• The high costs of advanced wastewater treatment
  plants.
• The demonstration that health risks and soil
  damage are minimal if the necessary precautions
  are taken

4
Technical Options for health Protection

• Treatment of Wastewater.
• Crop Restriction
• Application methods of wastewater.
• Control of human exposure.

5
Anaerobic Treatment Vs.Activated Sludge and Pond
Technologies in Jordon

• Some of the problems encountered in Amman
  activated sludge sewage treatment are
• - Very high volumetric energy consumption for
  aeration.
• - Huge sludge production per m3 of treated
  sewage.
• - Operational problems in the activated sludge
  plant (bulking sludge)
• Most of these can be ascribed to a too low design
  load but extension at the same location was
  impossible.

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Anaerobic Treatment Vs.Activated Sludge and Pond
Technologies in Jordon

• A solution was found in the construction of one
  of the worlds largest pond system
• The 200 ha As samra wastewater stabilisation
  pond.
• In a relativley short time, the pond was operated
  at higher loading rates than the design loads.
• Beside, the poor quality of the effluent (500
  mgCOD/l), all the problems listed above were
  encountered here.

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Anaerobic Treatment Vs.Activated Sludge and Pond
Technologies in Jordon

• Advantages of high-rate anaerobic treatment in
  comparison to conventional aerobic treatment
• Low investment costs and low space requirements.
• Applicable at small as well as large scale.
• Low production of excess sludge (up to 10 times
  less), which is well stabilised.
• No, or very low energy demand.
• Production of valuable energy in the form of
  methane.
• High loading capacity (about 5-10 times more than
  aerobic treatment)

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Anaerobic Treatment Vs.Activated Sludge and Pond
Technologies in Jordon

• Fate of carbon and energy in aerobic (left) and
  anaerobic (right) wastewater treatment

Anaerobic
Aerobic
2-10 Kg COD
100 kg COD
Sludge, 30-60 kg
10-20 kg COD
100kgCODAeration
Sludge, 5 Kg
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Integrated wastewater treatment in Faisalabad

• Description of the current system
• Pond system incorporating 4 anaerobic ponds, 6
  facultative ponds and 4 sludge storage ponds,
  with design flow of 90,000 m3/day.
• The area of each anaerobic pond is 2.75 ha.
• The area primary facultative ponds is 14.9 ha.
  each and the area of secondory and tertiary ponds
  is 17.4 ha. each

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Integrated wastewater treatment in Faisalabad
Western Domestic Sewage Treatment Ponds (WDSTP),
Faisalabad
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Integrated wastewater treatment in Faisalabad

• Design Modifications
• Alternative 1
• The flow from facultative pond 5 is diverted to 3
  and pond 6 is reserved for fish farming
• Pond 2 and 5 are used for duck weed cultivation.

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Integrated wastewater treatment in Faisalabad

• Alternative 2
• Ponds 2 and 5 are used for duckweed production
  and 3 and 6 for fish farming allowing small
  amount from 2 and 5 entering 3 and 6.
• Remaining water by passed directly to the
  effluent drain.

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Duckweed aquaculture in Faisalabad

• Temperature
• Minimum water temperature is reported to be 7 C,
  optimum growth between 25C and 31C, severe heat
  stress between 31C and 35C.
• Primary treatment
• Is essential for initial separation of the
  settleable fractions of pathogens, settleable
  solids and floating materials, which will be
  provided by the anaerobic ponds 1-6.
• Water Depth
• 20-25 cm is recommended as relatively shallow
  ponds facilitate better absorption of nutrients.
• Wind protection
• Duckweed is very susceptible to wind and water
  currents, stabilization of the plants on the
  water surface is of prime importance.

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Duckweed aquaculture in Faisalabad

• Labor Requirements
• Highly labor intensive, requires daily attention,
  regular skilled and expereinced labor ,
  sophisticated management to maintain optimal
  growth conditions for duckweed.
• Operation and maintenance work includes
  harvesting, feeding of duckweed and supplementary
  feed to fish in the adjacent farm fish, heat and
  wind stress management.

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Fish aquaculture in Faisalabad

• Fish culture is one mean of producing large
  amounts of proteins material in a relatively
  small amount of space.
• Reuse of treated sewage to fertilize the
  microbial food chain for aquaculture presents one
  of the most economic resource recovery option for
  developing countries.
• Quality of fish grown in San Juan lagoons in lima
  were determined to be acceptable for human
  consumption based on bacterial counts in the fish
  muscles.

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Economics of duckweed-fish pond system in
Faisalabad

• Assumed operating costs and earnings per hectare
  for sewage-duckweed-fish production at Faisalabad
  ponds system
• Item Amount in /ha
• Duckweed production
• Labor 1,300
• Bamboo grids 146
• Others 1,575
• Total Operating Cost (1) 3,021
• Fish Production
• Labor 1,300
• Lime/ Chemical 31.25
• Fingerlings 187.5
• Total Operational cost (2) 1,519
• Grand Total (12) 4540
• Gross earnings from the fish sale 4,900
• Gross Margin 360
• So a total gross margin of 360 /ha32 ha
  11,250 can be achieved.

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Design of SBR and A Stage of AB process for
wastewater treatment in Haroonabad

• Description of the current system
• Collapsed local sewarage system, resulted in the
  abandonment of the public pumping station.
• Wastewater is supplied to farmers for irrigating
  their lands which receive virtually no canal
  water.
• The rent of these lands is appreciably higher
  than normal canal water irrigated lands due to
  reasons of high yield.
• Crops grown on wastewaters are vegetables.
• Wastewater course is filled with sludge from time
  to time which requires frequent removal.

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Design of SBR and A Stage of AB process for
wastewater treatment in Haroonabad
The wastewater course carrying wastewater for
irrigation
The abandoned pumping station in Haroonabad
Wastewater mains at the operational pumping
station in Haroonabad
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Design of SBR and A Stage of AB process for
wastewater treatment in Haroonabad

• Process description
• SBR is a fill and draw activated sludge treatment
  system.
• The unit processes involved in SBR and activated
  sludge systems are identical.
• The A-stage has the following characteristics
• - A very high food-to-microorganisms (F/M) ratio
  resulting in high biological activity.
• - Very short hydraulic residence time (about 30
  min).
• - High BOD/COD removal efficiency at small
  treatment volumes.
• - Remove about 30 to 80 of the organic load
  entering the stage, making this stage alone
  sufficient for certain applications.

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Design of SBR and A stage of AB process for
wastewater treatment in Haroonabad
Effluent to irrigation
Suction pump
Compressor
Excess sludge to drying bed
Aeration

• Proposed modifications
• Conventional SBR 6 hours aeration and one hour
  settling
• A Stage 30 min aeration and one hour settling
  (4 times capacity)

Existing tank
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Rotating Biological Contactors at Channel No. 4
Faisalabad

• Channel 4 is a lined channel, 4 m wide, 0.6 m
  deep with 0.65 m/s velocity and discharge of 1.6
  m3/sec.
• One sewage plant was proposed, but its
  construction couldnt be initiated due to
  financial constraints.
• The estimated flows to the plant by year 2000 was
  2.83 m3/s.
• There is no other re-use of wastewater from
  channel 4 except wastewater irrigation.
• Farmers draw wastewater by drilling holes into
  the channel and using wastewater free of cost.

Channel 4 Faisalabad
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Rotating Biological Contactors at Channel No. 4
Faisalabad
Cross section along the channel equiped with RBC
Side view of the channel with the proposed RBC
system
The arrangement of the RBCs along the whole
channel
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Conclusions

• For the sake of feasibility, relatively simple
  technologies has been discussed here, including
  anaerobic treatment, SBR, A stage of AB process,
  RBC and aquaculture
• Hygiene after treatment reduction 2-3 log
  scales.
• Highest hygienic safty would require desinfection
  of treated wastewater, e.g. by UV or Ozonisation
• Maintenance and operation are the key issues for
  the success of these technologies
• Funding should be assured through adding the
  price of wastewater treatment to the drinking
  water costs.
• Awareness compaigns are needed with a key message
  to farmers that treated water is still containing
  most nutrients necassary for crops, with less
  pathogens and heavy metals
• Sludge will often be contaminated by heavy metals