Ile d'Yeu - France

A new generation of treatment plant, unequalled water quality

The remarkable site of Ile d'Yeu required a high performance treatment plant.

The chosen technology - odour and noise free - is compact, architecturally integrated, responsive to seasonal variations and outputs an exceptional quality of water. Thus protecting the natural environment of Ile d'Yeu for both residents and tourists.

Technical details

Effluents to be treated

		Capacity
Flow (1)		Winter	Summer
	m³/d	1120	2260
	m³/h	91	183
COD Chemical oxygen demand	kg/d	1080	3240
DBO₅ Biological oxygen demand	kg/d	390	1170
SS Suspended solids	kg/d	480	1440
TKN Total Kjeldahl nitrogen	kg/d	140	420
TP Total phosphorus	kg/d	29,5	88,5

(1) Including spurious waters

High-quality treated water

Maximum concentration over 24 h
COD	40 mg/l	Total coliforms	<1000/100 ml
DBO₅	10 mg/l	Heat tolerant coliforms	<1000/100 ml
SS	<5 mg/l	Faecal streptococci D	500/100 ml
TKN	5 mg/l	Phages ARN	<10/ml

Water circuit

Effluents are screened through a rotating strainer before clarification. The water is then transferred to an aeration tank, where bacteria consume carbonaceous and nitrogenous pollutants. The treated water is then filtered using membranes to remove suspended matter before being discharged to the sea.

The sludge is extracted from the membranes, dewatered and dried by solar energy and recycled for agriculture use.

Biosep™

Unequalled water quality

Operating principle

Biosep™ uses an aeration tank and a membrane system where membranes are located and grouped into modules. These modules are directly immersed in the aerated tank. The filtered water is extracted using two pipes and a third pipe is used in order to extract scouring air.

The membranes are hollow polymer fibres with a high mechanical resistance. Their break threshold is located between microfiltration and ultrafiltration (200 000 Daltons).

Filtering phase

The water is filtered from the outside to the inside because of a pressure difference generated by the height of water above the membranes. A draught pump completes this phase.

Back washing phase

The prevention of clogging and caking is managed through the extensive use of membranes (with low pressure through the membranes) and by ensuring that operating conditions are adapted to the treatment process (agitation using air scouring and back washing).