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Waste Stabilisation PondsProfessor D.D. Mara : University of Leeds

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The three types of WSP (normally preceded by pre-

treatment of screening and grit removal) are:

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WSP are arranged in series: an anaerobic and a facultative pond,

often followed by one or more maturation ponds. It is possible to

have more than one series at the same site.

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Phase I Dandora WSP, Nairobi, Kenya, comprising two series each

of a facultative and three maturation ponds. Sizes:

Each fac. pond: 700 x 300m. Each mat. Pond: 300 x 300m

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Melbourne, Australia. Two of the most recent series

here, each comprising an anaerobic pond, an aerated

lagoon and seven maturation ponds.

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Mze, near Montpellier, France: two small anaerobic ponds, four

experimental step-fed facultative ponds and a single series of a facultative

pond and four maturation ponds, discharge into the Bassin deThau a saltwater lagoon with commercial oyster beds.

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Village, near Rennes, France: single series of a

facultative and three maturation ponds. France

has >2500 WSP systems.

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Setbal, Portugal: a single series of an anaerobic, a

facultative and one maturation pond. Facultative pond

is baffled to improve hydraulic distribution.

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Ginebra, near Cali, Colombia: Acuavalle, the local water

and sewerage company, proudly announces that its

treating the towns wastewater!

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Ginebra: a 2-day anaerobic pond (top) and a 5-day

facultative pond (middle). The Facultative pond effluent

is used to irrigate sugar cane (bottom).

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Braslndia in the Federal District, Brazil: two series,

each comprising an anaerobic and a facultative pond.

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Fortaleza in northeast Brazil: a single series of an

anaerobic, a facultative and three maturation ponds

(poor physical design as anaerobic pond is 30m x 1km!)

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Tigh Mor Trossachs, Perthshire, UK: a single series of a facultative

pond and two maturation ponds, serving the holiday home

complex (top). The UK has about 30 WSP systems.

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Quebec, Canada: here, even in winter,

ponds work well.

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Close-up of a facultative pond dark green because of

the algae which grow naturally and profusely in it.

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A US EPA poster showing some of the algae found in WSP.

The algae with flagellae (tails) are most commonly found

in facultative ponds; others in maturation ponds.

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Algal-bacterial mutualism in facultative and maturation ponds: the

algae supply the oxygen (by photosynthesis) for the bacteria to

oxidise the organic compounds in the wastewater, and the bacteriaproduce CO2 for the algae to fix into new cellular material.

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US figures for electrical energy consumption by various

wastewater treatment processes. WSP do not need

electrical energy as the algae utilise solar energy directly.

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Pond construction is relatively simple: the main

civil works is earthmoving.

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Ponds may need lining with a plastic membrane if the

soil is too permeable (>10-6 m/s).

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Ponds are good in tourist areas: in summer they

can treat 2-3x the wastewater flow from

the winter population.

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Ponds have these advantages. Their only

disadvantage is that they require more land than other

wastewater treatment processes.