Waste water reuse on forestry plantation (Nègrepelisse)

CCTVA operates Negrepelisse sludge treatment unit. Sludge is treated by several filters. Between May and October, the treatment plant provides water to a forestry plantation. This operating increases the treatment of effluents and produce firewood for the communal heat production plant. An experimental monitoring has been initiated in 2014 for 3 years, to assess the performances of sludge treatment, tree growth and performance of the irrigation system.

This is the best way to reuse waste water in accordance with French regulation. The reuse allows decreasing discharge impact in the river, and increasing the growth of trees which means a better way to produce energy.

In the future, is there any new expected use for this water reclamation project?

There isn’t other use expected because of regulation, but it should be interesting to think about cleaning street.

The project is born because of lack of sludge treatment plant in north east of department. This situation was source of several issues such as outlawed discharge, difficulties for monitoring sludge spreading plan, transports over long distance.

Implementation costs: the cost operation is about 1,9 million euros.

• Property purchase:4%
• Treatment:79%
• Irrigation:14%
• Experimental equipment: 3%

Reuse waste water has been allowed for testing reason and only if the following conditions were respected:

• the plantation must be inaccessible for public,
• the irrigation system must avoid spray,
• the environmental monitoring (groundwater, surface water)

The innovative aspect concerned :

• The sludge treatment using common reed, on this scale (11 000m3/year)
• The reuse of water coming from sludge treatment ;
• The way to provide water to the plantation (microsprinkling and ajutage)

The social benefits haven’t been clearly identified. At the beginning, neighborhood was quiet anxious. He scared mainly of smell coming from sludge. Now, after one year operating, we have never been alerted about any smell production. The treatment plant and water reuse seem well accepted by neighborhood. We can note that the few people who know this project are quiet proud to live on a dynamic territory.

The reuse avoids impact of discharge at the summer time, period where the river is the most sensitive.

About economics aspects, water reuse signifies more investment (10 to 12% of total cost.) The cost of exploitation is around 5 000 euros per years and includes monitoring and energy consumption. The finality of plantation is to provide fire wood for the communal heat production plant. The production is expected between 15 and 20 tonnes dry matter/hectare after 1 years, which means the biomass production could be 1,5 to 2 higher than that is usually observed on these species without irrigation.

Reuse reduces the cost of irrigation which is around 0,5 €/m3.

The mains obstacles to take account are :

• Regulation’s obligations ;
• Acceptation by local people;
• The cost of investment.

CCTVA will provide technical data about exploitation (problems, costs, first tendency about irrigation and treatment monitoring, etc.)

CCTVA is in deal with Ecofilae to discuss about the meeting in France (date and place.)

CCTVA is communicating about Alera project on his web site (site Internet)