- Treat domestic waste
- The regulatory context of non-collective sanitation (NCA)
- And its recent evolutions
- Controls of the SPANC (Public Service of Non Collective Sanitation)
- Environmental or health issue?
- Risk: a broad notion
- Water agencies: goal 2015
- Owners: which obligations regarding sanitation?
- The opinion of an expert: Luc Lary *
- The opinion of an expert: Thierry Koerckel *
- Autonomous sanitation: how does it work?
- How to determine the permeability of the soil?
- Good to know: the limits of non-collective sanitation
- Pipe evacuation
- Polyethylene pit
- Vertical sand filter
- Underground spreading
- Tier of infiltration
- Gravity filter
- Micro-purification station
- A guide to help with the choice for autonomous sanitation
- Glossary of the ANC (non collective sanitation)
- Internet sites to consult to find out more about the treatment of domestic waste
Recent regulatory developments place new obligations on homeowners who are not connected to the public network. Overview of the consequences and main solutions to remember.
Treat domestic waste
The treatment of domestic discharges is as much the objective of the protection of groundwater and surface water as that of populations against any health risk. This is why agglomerations have sewer systems and sewage treatment plants. We then speak ofcollective sanitation facilities.
Largely majority today, this mode of treatment can however be implemented in certain zones (rural, periurban...) for reasons of cost. As a result, nearly 6.5 million dwellings (12 million inhabitants!) Still fall under thenon-collective sanitation (ANC). This type of treatment consists in purifying the on-site discharges using an autonomous die.
The regulatory context of non-collective sanitation (NCA)
Old enough in principle, non-collective sanitation has only been officially recognized for twenty years. It is indeed a European Directive of 1991 then the 1992 Water Act who have made it a valid alternative to "sewerage". But only under certain conditions: users must have facilities that comply with the law and keep them in good working order.
In principle, all these facilities should have been checked at least once before the end of 2012... This mission was originally the responsibility of the town halls, DDASS or DDE. But since Water and Aquatic Environment Act (LEMA) 2006this responsibility has been transferred (for any municipality of more than 2 000 inhabitants) to SPANC (public sanitation services). SPANCs decide on a case-by-case basis on the choice of this or that die, and control its design and implementation. They rely for this on the Grenelle 1 and 2 laws as well as on various standards.
And its recent evolutions
Most of the regulatory provisions applicable today are in theinterministerial decree of September 7, 2009. It was completed in 2012 by two other texts of the same type.
TheOrder of 7 March 2012 adds the obligation for owners to contact SPANC before any remediation project. This text also distinguishes existing installations, new installations: that is to say realized or rehabilitated from 1st July 2012. It also specifies the calculation of their dimensioning: the selected unit (number of equivalent-inhabitants or EH) corresponding to the number of main rooms of the housing, except special case justifying a preliminary study.
The decree of April 27, 2012 (entered into force on 1st July) aims to improve the quality of the installations from the moment they are designed and to prioritize the rehabilitation of installations with health hazards or proven risks for the environment.
Controls of the SPANC (Public Service of Non Collective Sanitation)
Each installation is subject to a periodic inspection of the SPANC (Public Non Collective Sanitation Service) to verify its operation and maintenance.
Since the law Grenelle 2 of July 12, 2010, the frequency of this control increases to 10 years, against 8 years ago. According to the national surveys carried out each year by theNational Association for the Defense of Consumers and Users (CLCV) at 80 SPANC *, these checks are much more frequent: 96% of them take place before 8 years, 38% of which every 4 years... This is not without consequence for the user who pays an average of € 85 per check, with differences of 1 to 15 depending on the SPANC on which it depends.
Conclusion: we can not advise everyone to remain vigilant and compare their experience with those of other users, via a local association, for example.
* "ANC black folder: a dive in troubled waters" clcv.org/themes/welcome-on-the-space-consolidation-national. html
Environmental or health issue?
TheOrder of April 27, 2012 indicates the list of points to be checked (at least) by the SPANC of new or rehabilitated installations. The other existing installations must be subject to almost all the same checks, to which are added many others (see the text of the decree **). This text also specifies the context of these controls and distinguishes for this several areas: environmental issue or health issue. The notion of zone extends from the site of the installation to the place where the rejections reach the natural environment after treatment.
Areas of environmental concern are identified as such by the master plan of development and water management (SDAGE) or the scheme of development and water management (SAGE). Both are under water agencies.
Areas of health concern on the other hand, they are characterized by the proximity of a public catchment for human consumption, a bathing site or nautical activities, shellfish farming, fish farming, cress farming, fishing on foot...
** The decree can be downloaded from the Légifrance website (Public Law Distribution Service): legifrance.gouv.fr. Click on "Other Legislation and Regulations" and then in the "NOR" box, type "DEVL1205609A".
Nitrates and pesticides remain the main contributors to the poor state of water in the natural environment. Effluents from domestic installations account for only 1% of the diffuse pollution of French waters (source: the CLCV consumer association).
Risk: a broad notion
The decree of 27 April 2012 also distinguishes danger to the health of people that can present an autonomous installation: defect of sanitary security (leaks), defect of structure or closure (falls).
In a health zone, the concept of risk extends to lack of performance due to incomplete installation, which is significantly under-sized or has major malfunctions.
In an environmental zonesuch factors constitute a risk of pollution of the environment.
But remember that according to the law Grenelle 2 andOrder of April 27, 2012, « the proven risk is established on the basis of evidence (studies, environmental analyzes carried out by the State services or water agencies) that demonstrate the impact on downstream or environmental use. If the information available to the controller does not allow him to conclude with certainty, the installation will not be considered as having a proven risk of pollution of the environment. »
Water agencies: goal 2015
Six water agencies (also called basin agencies) depend on the Ministry of Ecology, Sustainable Development and Energy (MEDDE).
Their mission is to reduce pollution from all sources and protect the water and aquatic resources of the seven metropolitan watersheds. They thus collect royalties (environmental tax revenues), via the users' water bills (individuals, communities, etc.).
Their objective: two-thirds of water bodies in good condition by 2015 (law Grenelle 1). But for the moment, only about half of the water is in "good chemical status", 43% of surface water (rivers, lakes and coastal waters) and 59% of groundwater *.
* Source: MEDDE.
Owners: which obligations regarding sanitation?
Depending on the nature of the problem and the risk it represents, the obligations are not the same for the owner.
From the simple recommendation to improve the operation of the installation, it may go as far as the notice to carry out a compliant installation as soon as possible.
In addition there are more general provisions, among others: to ensure the regular maintenance and to proceed to the emptying by an authorized person, to allow the agents of sanitation to reach the installation, to append to the promise of sale a report control issued by the SPANC less than 3 years... And from now on, SPANC's opinion is also involved in issuing a building permit.
The opinion of an expert: Luc Lary *
It is not because a sewerage system is approved that it gives satisfaction.
It must be dimensioned correctly and not be chosen "a minimum", on the sole criterion of price. An operating cost of 500 € / year can quickly become intolerable for some households. Hence the risk of neglected maintenance, declining performance and negative consequences for the environment... "
* Luc Lary, head of water treatment products within the Sebico Group (93).
The opinion of an expert: Thierry Koerckel *
Many conventional channels, with all-water pit, underground spreading bed, sand filter..., are now saturated and must be brought up to standard.
The new approved sectors therefore have their cards to play: one to two days are enough to implement them (against nearly a week for traditional systems), and they have a minimal impact on the ground. It can be predicted that within 5 years, perhaps before, they will have supplanted conventional solutions, especially in new construction. "
* Thierry Koerckel, Head of Technical Service and Graf Design Office (67).
Autonomous sanitation: how does it work?
Domestic discharges or effluents are made up of greywater from sinks and toilets, and black water coming from toilets. Both must undergo a two-stage treatment (pre-treatment and treatment).
The pretreatment has the effect of retaining the oils and greases in a special tray located upstream of the pit "all waters".
Degreased, the greywater joins the water-valves which, they go directly to the pit. Heavier materials accumulate in the bottom of the pit in the form of sludge. Thanks to anaerobic bacteria (living without oxygen), their volume is gradually reduced by fermentation. But emptying is necessary.
The clearest waters remain on the surface and pass through a prefilter (called decolloid) mounted at the exit of the pit. The effluents are then ready for aerobic treatment (containing oxygen). This last stage of sanitation aims to break down the final residues of organic matter. This process takes place in a treatment device using the soil purifying power.
How to determine the permeability of the soil?
|Infiltration time||Nature of the land||Coef. permeability k * (in mm / h)|
|Less than 30 minutes||Sandy soil||k> 50 (high permeability)|
|30 min to 2 h||Sandy-loam soil||30 ≤ k ≤ 50 (average permeability)|
|2 am to 4 pm||Loamy soil||15 ≤ k ≤ 30 (poor permeability)|
|More than 4 hours||Clay-silty soil||6 ≤ k ≤ 15 (low permeability)|
To measure the permeability of your land, dig a hole about 30 x 30 cm at 50 cm depth. Fill it with water and wait until it is completely absorbed by the soil. Pour 10 liters of water again and measure the infiltration time.
* The permeability coefficient k (or hydraulic conductivity) expresses an infiltrated water height per unit of time according to the Porchet test (so-called constant level percolation test).
Good to know: the limits of non-collective sanitation
Non-collective sanitation facilities are designed to receive a gross organic pollution load of up to 1.2 kg of BOD5 per day. Approved, they must not discharge more than 35 mg / l of BOD5 and 30 mg / l of suspended solids (suspended solids) per day, according to the decree of 7/9/2009 (article 7).
A PVC pipe 100 mm Ø allows aeration of the septic tank. The evacuation must exceed the roof of 40 cm minimum.
This polyethylene pit of 3,000 to 6,000 l includes a diffuser that limits the eddies entering the effluents and a prefilter output. It also offers good performance in case of near water table.
Vertical sand filter
For which lands?Privileged for clay soils, an undrained sand filter consists of a 70 cm thick sand bed. covered with 20 cm of gravel and sometimes deposited on a geotextile felt.
Drained, the sand is preceded by a layer of 10 cm of gravel and a collection drain.
At what price?4,500 to 6,500 € HT (undrained) / 5,000 to 10,000 € HT (drained) for 5 population equivalents (see glossary page 23).
AdvantagesThis solution mitigates the lack of permeability of a soil. In undrained version, it adapts to the presence of water at 80 cm deep. An impervious film can also be placed under the drainage layer to protect the water table (cracked ground).
disadvantagesThe surface and the depth of a sand filter are equivalent to those of a conventional underground spreading bed (200 m2). The sand must also be fine enough to ensure good dispersion and optimal long-term operation.
For which lands?
Underground spreading is a solution adapted to large permeable soils (classical solution). It generally consists of parallel trenches 15 to 30 m long and 0.60 to 1 m deep. At least 1.50 m apart, they house the spreading pipes on a bed of gravel. These tubes are interconnected by looping and distribution eyes and then covered with a geotextile felt and top soil. Variant: the spreading bed in the form of a dig. This is the option considered in the case of sandy soil or where trenching can not be done for any reason.
At what price?4,000 to 6,000 € HT for 5 population equivalents.
AdvantagesTrenches or spreading bed, the device well known to professionals, has largely proven itself. It is also one of the cheapest.
disadvantagesThe ground must be sufficiently permeable (k * ≥ 50 mm / h at 60 cm depth) and free of water between 80 cm and 1.5 m deep. A search requires at least 60 m2 and trenches an area of about 200 m2. This type of solution is therefore reserved for a fairly large field; knowing that we must also count with the surface of the all-water pit and the grease trap. The land must also be flat (less than 2% slope) and free of tall trees, ornamental massifs and other irremovable elements (swimming pool, rainwater tank, oil tank...).
* K = coefficient of permeability of a terrain.
Tier of infiltration
For which lands?The infiltration mound is suitable for sloping terrain or with an open water table.
It takes the principle of the vertical sand filter undrained but instead of being implemented in the depths of a search, it takes place above the ground. The height of the structure easily reaches 1 m or more, because it takes at least 70 cm of sand.
At what price?€ 8,000 to € 12,000 excluding tax for 5 population equivalents.
AdvantagesThis process does not require any excavation. It is therefore suitable for impervious sites or located in a flood zone or with water at 80 cm deep.
It is also suitable for terraced plots.
disadvantagesAn infiltration mound requires an area equivalent to that of a sand filter (200 m2). In addition, it significantly modifies the topography of places.It can also impose the presence of a lift pump, so an electrical connection. Its cost may also vary depending on the availability of sand required.
For which lands?For small sites, the gravity treatment has the particularity to allow the direct dispersion of the effluents in a superficial hydraulic medium (wet ditch or watercourse for example) by infiltration in the ground, or even in a collection network of rainwater. It uses a gravity filter through which the partially decanted effluents pass through the prefilter of the all-water pit. This tank accommodates bacterial media or a filtering substance (chips of coconut fibers, rockwool, calibrated sand...) which allows the purification to be completed normally.
At what price?€ 8,000 to € 12,000 excluding tax for 5 population equivalents (see glossary opposite).
AdvantagesSpace saving. A gravity filter occupies only 10 to 15 m2 in general. It can also be used above ground (under a hillock) and powered by a lift pump and sometimes be split (parallel assembly) to serve multiple homes (grouped ANC). Some filtering substances are recyclable.
disadvantagesThe filter material is periodically (pumped) to be replaced at a frequency that depends on the design.
For which lands?For problem areas (very small, rocky, inaccessible...), a micro-station is installed, depending on the case, in addition to a pit all waters or replaces alone all components of a wastewater treatment system (all-out pit) It is then partitioned into two or three rooms: upstream or downstream or concentric. The upstream or central chamber serves as a primary clarifier for pre-treatment. The downstream or peripheral chamber provides the treatment. Some micro-stations operate in a static manner with a filter substance, such as a gravity filter. Others use a submerged recirculation pump and still others run on compressed air (with a small compressor controlled by a control cabinet).
At what price?€ 6,000 to € 10,000 excluding tax for 5 population equivalents (EH).
AdvantagesAn unmatched compactness (less than 4 m2 for some models) that is perfect for renovation and problem grounds.
disadvantagesAbout the same as the gravity filter, and a more complex maintenance which, in the majority of cases, justifies a maintenance contract.
A guide to help with the choice for autonomous sanitation
The Interministerial Site on Non-Collective Sanitation offers a "Facility Information Guide", available for free *. It allows users to take stock of all technical and practical aspects: from the design to the completion of an installation, through the financing of a renovation. This can be the subject of a zero-interest eco-loan (Éco-PTZ) up to a limit of € 10,000. Other subsidies are also possible (water agencies, general councils, municipalities, National Agency for Housing). For more information, consult the SPANC of your region (spanc.fr).
* assainissement-non-collective. developpement-durable.gouv.fr/ user-tools-information-a502.html
Glossary of the ANC (non collective sanitation)
BOD5: biochemical oxygen demand over 5 days. It is used to measure biodegradable pollution. It corresponds to 5 days of oxygen consumption of the microorganisms responsible for decomposing the effluents.
Population Equivalent (PE): amount of pollution emitted per person, ie 60 g of BOD5 per day for 150 l / d of wastewater flow. Since the decree of March 7, 2012, 1 EH = 1 main room.
Spreader: PVC pipe perforated along its length which ensures the treatment of aerobic effluents and their dispersion in the natural environment.
Suspended matter (MES): undissolved fine substances of mineral or organic origin. Visible to the naked eye, they can degrade the quality of the surface waters.
Spankers: Public sanitation services technicians (SPANC).
Internet sites to consult to find out more about the treatment of domestic waste
• Interministerial site on non-collective sanitation: assainissement-noncollectif. sustainable development. gouv.fr
• National Consumer and User Advocacy Association (CLCV): clcv.org/themes/ welcome-on-lespaceanc- sanitation-noncollective. html.
• Water France (Public Water Information Service): eaufrance.fr