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18 Cards in this Set

  • Front
  • Back

waste stabilisation ponds Advantages

-low capital cost and easy to design

-low operating and maintenance cost

-high level pathogen kill

-robust system

-can deal with load fluctuations due to long retention periods.

- resource recovery via algae harvest

-bio-gas generation in anaerobic ponds

waste stabilisation ponds disadvantages

-large land area requirement

-inconsistent nutrient removal

-lack of engineering process control

-performance influenced by climate

Types of ponds

- anaerobic




-first pond in series

-high organic loading

-40-70% BOD removal

-2-5m deep, no algae

Anaerobic pond

Facultative pond

- most common pond type

- primary or secondary pond

- 1.5m depth

- contains anaerobic and aerobic zones.

faculatative pond

Maturation pond

- last in series

- polishing treatment

- pathogen and nutrient removal

- 1.5m deep

Pond treatment: Organics

-Primary settling occurs in the first pond

- they get anaerobically decayed in sludge layer

Pond treatment: pathogen removal

- high pathogen removal

Due to

- long retention time

-high PH

-Exposure to sunlight

-Oxygen presence

-competition by microbes

Pond treatment: Nitrogen and phosphorus removal

-60-80% removal

-removed by assimilation, biological nitrification/denitrification, settlement an removal of solids

-chemical precipitation at high ph

-biological uptake by algae

anaerobic pond design

Facultative pond design

maturation pond design

Wetlands advantages

- low capital and operating cost

- ease of operation

- minimal mechanical and electrical components

types of wetlands

1. surface flow

2. sub-surface flow

surface flow

-water passes through stem of plants.

- larger than subsurface flow wetland.

Subsurface flow

-water passes through media and past root zone-Aesthetically pleasing