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Definition of indicator
The objective, in this case, is the desired treatment or modification of the input sludge before disposal or reuser.
How to measure or calculate it ?
If possible, revise design document and ask to the design team or consultants: the objective should have been considered to design and dimension the faecal sludge treatment site. Usually, the objective is related to the quality of input sludge and the environmental conditions of disposal sites or the desired reusing methodology.
Why it is important to measure it
This is very important to design the faecal sludge treatment site and to evaluate the efficacy of the treatment.
Definition of Indicator
This indicator defines at the moment of design how long the faecal sludge treatment site should be operational..
How to measure or calculate it ?
Identify immediate and long term needs. Analyse population growth and movements trends (see design beneficiary indicator), donors and implementing actors commitments.
References, tips, examples
The size of the population today might be 1,000 persons (often referred to as ‘capita’), but in 1 year this may double and in 5 years this might increase ten-fold; moreover it is important to know how long the facility will need to last to determine the building materials to use.
Why it is important to measure it ?
It is important to know the design period as this will help to calculate the designed beneficiary population (see indicator) of the faecal sludge treatment site. Moreover, it is important to know how long the facility will need to last to determine the building materials to use.
Definition of indicator
This indicates the level of knowledge and experience required to be able to design faecal sludge treatment site successfully.
How to measure or calculate it ?
The indicator is determined by assessing the design process and understanding if specialists were involved or not.
References, tips and/or examples
Example of different design skills in the same context: Design of large scale faecal sludge treatment site of Oxfam in Cox Bazar was implemented in collaboration with Borda (sanitation experts). The small lime stabilization faecal treatment site of Oxfam was implemented by the ‘regular’ WASH officers.
However it’s always preferable to check designs with FSM specialists as in practice the law of Murphy rules: anything that can go wrong, will go wrong.
So for example also during the design of a simple facility such as a septic tank the following mistakes are common:
– inlet and outlet are mixed up;
– plans and cross-sections are mixed up;
– capacity of the facility is far too large;
– absence of ventilation pipes;
– absence of infiltration facilities;
– leaking tanks;
Etc., etc. etc.
Why it is important to measure it ?
Faecal sludge is a potentially dangerous material: a simple mistake impacts the lives of many people
This indicator is important for actors interested in implementing faecal sludge treatment for planning reasons.
Definition of indicator
The indicator defines if the technology also works well if ground-water is less than 1 metre from ground levelat least for a part of the year
How to measure or calculate it ?
Check, at the end of rainy season, the groundwater table at the faecal sludge site by digging a pit and/or checking dug wells nearby (in the early morning before water is taken and water level drops).
If it’s not possible to do it at the end of rainy season, ask for information from the local population about water level in the wells during the year.
References, tips, examples
In areas with high water tables, it might be a challenge to dig pits/ tanks as pumps for keeping the pit dry might be absent. Even if pumps are available, care must be taken to avoid floating of empty tanks. Floating can be avoided by adding enough weight (stones, concrete) to the tank to prevent floating. Hence, above ground / raised facilities are advised such as raised Oxfam tanks.
Why it is important to measure it ?
Faecal sludge is potentially dangerous material and when in contact with water, contaminants will spread easily and quickly. Moreover, construction in areas with high ground water table requires extra measures and more complex structures (expensive).
Definition of indicator
It defines the type of sanitation infrastructures from which the sludge comes from
How to measure or calculate it ?
If existing, analyse the documents of desludging which report this information, otherwise observe the desludging activities and the sanitation infrastructures from which the sludge comes from. Talk with people in charge of desludging.
References, tips, examples
Hospitainer has developed specific solutions for hazardous hospital waste in the framework of S(p) eedkits : https://hospitainer.com/add-ons/sanitation/ . Both IBBK and A-aqua have developed sludge pasteurizers: http://www.a-aqua.no/Products-Services/Humanitarian-Aid/Hygieniser100-Sludge-Pasteurising-Unit ;
Why it is important to measure it ?
It is important to know the source to estimate the characteristics of the sludge and likeliness of contamination with pathogens (of course, any faecal sludge needs to be treated as hazardous material but waste from hospitals is likely to be more hazardous and needs special attention.)
Definition of indicator
Number of people who can benefit from the faecal sludge treatment service.
How to measure or calculate it ?
Analyse current population, its growth and movement trends. In a stable growing population, population to be served can be calculated as follows:
Pn = P0 * (1+i)^n
Pn = Population in year ‘n’ (refer to life expectancy indicator)
n = design period
P0 = Population in year 0
i = annual growth of the population
However in humanitarian context, this will usually depend on the security context (forecast of the population affected by the natural /manmade disaster).
References, tips, examples
Example:
n = design period (say 5 years)
P0 = Population in year 0 (say 1,000)
i = annual growth of the population (say 10% influx per year)]
P5 = 1,000 * (1+0.1)^5 = 1,610 persons, say 1,600
Why it is important to measure it ?
When the population is known, there is a solid basis for sizing the facility: sizing of the tanks AND sizing of any pumps, drying beds, etc.
Definition of indicator
This is the space occupied by the faecal sludge treatment site in relationship with the design beneficiary population (see indicator).
How to measure or calculate it ?
Measure in the field, or in the project designs, the total area of the faecal sludge treatment site and divide it by the design beneficiary population (see indicator).
Why it is important to measure it ?
In humanitarian contexts, the population is often obliged to settle in crowed areas with unfavourable environmental conditions. This has a consequence also on the availability of space for faecal sludge treatment sites and sanitation facilities in general.
Definition of indicator
This indicator, in this case, defines the general slope of the area of the sludge treatment site.
How to measure or calculate it ?
If some types of topography are equally present, please provide multiple answers.
Why it is important to measure it ?
The topography may determine the type of treatment facilities to be built and may influence the transport and pumping costs.
Definition of indicator
This indicator defines for which sludge flow the facility has been designed.
How to measure or calculate it ?
If possible, revise design calculation document and ask the design team or consultants. The design input flow should have been considered for dimensioning. Usually, if it’s not possible to measure in the field, the input flow is estimated as follows:
For emergency simple pit latrines emptied at regular intervals and with poor pit infiltration: it is estimated 2.2 lcd (1 for anal cleansing and toilet cleaning + 1.2 for faeces)
For emergency simple pits where effluent can infiltrate and latrines are emptied at regular intervals consider the following sludge accumulation rates:
Wastes retained in water where water is used as anal cleansing material: 25 litres per capita per year (lcy);
Wastes retained in water where degradable anal cleansing materials are used: 40lcy;
Wastes retained in water where non-degradable anal cleansing materials are used: 60lcy;
Wastes retained in dry conditions where degradable anal cleansing materials are used: 60lcy;
Wastes retained in dry conditions where non-degradable anal cleansing materials are used: 90lcy;
For pour-flush facilities where water cannot infiltrate, emptied at regular intervals: it is estimated 4.2 lcd (2 for additional flush water),
For small network (small bore sewerage, solids free sewerage) where domestic drinking water network is available: it is estimated 80% of the drinking water supply ends up in the sanitation system.
For some environmental conditions and infrastructures, groundwater infiltration inside the sanitation facilities should have been considered.
References, tips, examples
Example:
Simple pit latrines emptied at regular intervals and with poor pit infiltration: only water used for anal cleansing and cleaning the toilet enters the receptacle together with the volume of urine and faeces. Typical volume for anal cleansing is 1 litre per person per day (lcd or litres per capita per day). Typical volumes of fresh urine and faeces 1.2 lcd. Hence, for 1.000 people: 1.000 * (1+1.2) = 2,200 litres or 2.2 m3/day;
Pour-flush facility where water cannot infiltrate, emptied at regular intervals: water used for anal cleansing AND manually flushing the toilet enters the receptacle. Typical volume for pour-flush is 2-3 lcd. Hence, for 1,000 people: 1,000 * (3+1.2) = 4,200 litres or 4.2 m3/day;
Small network (small bore sewerage, solids free sewerage) where domestic drinking water network is available. When wastewater is collected and conveyed and treated, usually taken as 80% of the drinking water supply ends up in the system. Hence, if for example drinking water is 25lcd, wastewater is 25 * 0.8 = 20lcd. Hence, for 1,000 people: 1,000 * 20 = 20,000 litres or 20 m3/day.
Why it is important to measure it ?
When the design flow is known, there is a solid basis for sizing the facility: sizing of the tanks AND sizing of any pumps, drying beds, etc. Sludge can easily be much more than the volume of urine and faeces and has a big impact on the sizing. If this is neglected, the facilities are too small and retention / treatment times are shortened, resulting in poor results.
Definition of indicator
The indicator defines if the main outputs of the faecal sludge treatment site are composed only of sludge, effluent or both
How to measure or calculate it ?
Observe if two different outputs originating from solid/liquid separation mechanisms can be distinguished on the basis of their density and solids content.
References, tips, examples
For example, the ratio between the two in the simplest treatment system (sludge drying beds) has been assessed as following:
septage (contents of a septic tank) % of solids (typically 1-2 %)
faecal sludge from pit latrines with a high % of solids (typically 10-15%).
Solids content is an important parameter to estimate the volume of dried sludge to be removed from the drying beds of sludge treatment plants. After 2 weeks drying period the typical solids content is 40% dry solids. Hence, 1 m3 (1,000 litres) of septage containing 1% of dry solids has been decreased to 1,000 *1%/(40%) = 25 kg of biosolids. The remainder (typically 1,000-25 = 975 litres has partially evaporated, partially drained away. The drainage water, say max 975 litres, needs to be treated in a filter / pond system. Also, 1 m3 (1,000 litres) of faecal sludge containing 15% of dry solids has been decreased to 1,000 *15%/(40%) = 375 kg of biosolids. The remainder (typically 1,000-375 = 625 litres has partially evaporated, partially drained away. The drainage water, say max 625 litres, needs to be treated in a filter / pond system
Why it is important to measure it ?
Knowing if there are different outputs enables the creation of specific different treatment chains and disposal mechanisms.
Definition of indicator
Locally available material is material that doesn’t need to be imported.
How to measure or calculate it ?
Analyse the purchase documents for the faecal sludge treatment site and equipment and identify material imported from abroad.
References, tips, examples
Typical imported materials are the raised latrines discussed above, Oxfam tanks for sludge treatment (e.g. lime treatment) and a ‘plug-and-play’ wastewater treatment plant for a hospital.
Why it is important to measure it ?
During the first few days of an emergency, it might be difficult to source local material. Hence, these need to be flown in. However, locally available material should as much as possible be sourced to reduce construction costs.
Definition of indicator
Barrier which doesn’t allow entrance to the faecal sludge treatment site for people, animals, vehicles who are not involved in the treatment operations.
How to measure or calculate it ?
Observe if a fencing is in place all along the perimeter of the faecal sludge treatment site. Identify if there are any weak points which allow people, animals, or vehicles who are not involved in the treatment operations to enter the site.
Why it is important to measure it ?
Adequate fencing is a must under all circumstances in conjunction with 24/7 guards: septage, wastewater and faecal sludge are hazardous material and can easily be used to contaminate the entire community. Think of vandalism by punching a hole in a bladder full of sludge.
Definition of indicator
Drainage are all the systems that avoid water logging and the entrance of run-off water to the faecal sludge treatment site.
How to measure or calculate it ?
Observe if there are specific infrastructures for drainage in the faecal sludge treatment site. Identify if there is any major waterlogging or water run-off which causes surface water contamination or makes the treatment operations difficult.
Why it is important to measure it ?
Adequate drainage is a must under all circumstances to prevent flooding and lead storm water away from the site without major contamination.
Definition of indicator
The indicator defines if the area of the faecal sludge treatment site is affected by flood.
How to measure or calculate it ?
Verify with literature and local knowledge when last flood occurred in the faecal sludge treatment site. The indicator defines if the area of the faecal sludge treatment site has been affected in the last period equivalent to the life expectancy (see indicator) and nothing has been done to avoid flood in the area during construction. The indicator takes in consideration only the faecal sludge treatment site and not the access to it or to latrines.
Why it is important to measure it ?
Faecal sludge is a potentially dangerous material: flooding may stop operations for several weeks and/or spread faecal contamination out of the faecal sludge treatment site.
Definition of indicator
This indicator defines the total of:
– Preliminary and general items (Office and transport contractor and supervisors, security, insurance, electricity supply connection, etc.)
– Purchase of land
– Civil works
– Electromechanical works: pumps, GenSet,
– Design (typically 5% of Civil & Electromechanical costs)
– Supervision of implementation (typically 5-15% of Civil and Electromechanical costs)
divided by current flow.
How to measure or calculate it ?
All the expenditure for the construction and put in place of sludge faecal treatment system have to be considered and divided by the real input flow (see indicator). It includes also a quota of human resources involved in the conception and construction, that can have been involved also in other tasks.
References, tips, examples
A treatment plant in inaccessible areas where cement bags need to flown is easily 10 times more expensive than the same plant in areas where cement can be purchased ‘of the shelf’.
Why it is important to measure it ?
Capital expenditure per real input flow on any faecal sludge treatment site differ from place to place and depends mostly on transport costs.
Definition of indicator
This indicator defines the total of:
– Preliminary and general items (Office and transport contractor and supervisors, security, insurance, electricity supply connection, etc.)
– Civil works
– Electromechanical works: pumps, GenSet,
– Design (typically 5% of Civil & Electromechanical costs)
– Supervision of implementation (typically 5-15% of Civil and Electromechanical costs)
divided by current flow.
How to measure or calculate it ?
All the expenditure for the construction and installation of the faecal sludge treatment system (EXLUDING PURCHASE OF LAND) has to be considered and divided by the real input flow (see indicator). It includes also a quota of human resources involved in the conception and construction, that can also have been involved in other tasks.
References, tips, examples
A treatment plant in inaccessible areas where cement bags need to be flown in is easily 10 times more expensive than the same plant in areas where cement can be purchased ‘off the shelf’.
Why it is important to measure it ?
Capital expenditure per real input flow on any faecal sludge treatment site differs from place to place and depends mostly on transport costs.
Definition of indicator
This indicator defines the level of knowledge and experience required to be able to build a faecal sludge treatment site successfully.
How to measure or calculate it ?
The indicator is determined by assessing the construction process (including selection of contractors or construction staff) and understanding if specific contractors and specialists for special supervision, know-how, equipment were involved or not.
References, tips, examples
Skill level for construction can be reduced by standardization, use of kits and clear and univocal instruction materials.
Why it is important to measure it ?
Faecal sludge is a potentially dangerous material: a simple mistake in infrastructures construction may stop operations for several weeks and affect the sustainability of faecal sludge treatment.
Definition of indicator
Operation expenditure includes the daily average of:
– Staff costs
– Energy costs (especially high when electricity needs to be generated separately)
– Chemical costs
– Transport costs
– Administration costs
– Water for cleaning / operating costs
– Personal Protection Equipment costs
– Etc.
divided by real input flow.
It doesn’t include desludging costs.
How to measure or calculate it ?
All the expenditure for operations has to be considered and divided by the real input flow (see indicator). Also expenditures for extraordinary operations as a daily average should be considered. It also includes a quota of human resources involved in the operations, that can also be involved in other tasks.
References, tips, examples
Typical O&M costs for faecal sludge treatment around the world are USD 6-10 /m3.
Why it is important to measure it ?
It represents the economical efficiency of the faecal sludge treatment systems by comparing daily operational costs with real input flow.
Definition of indicator
This indicator defines the skill level of the manager of the O&M tasks of the faecal sludge treatment site.
How to measure or calculate it ?
Analyse the CV of the manager of the O&M of the faecal sludge treatment site and identify if he/she has an education higher than the compulsory one (high school, university) and if this education is strictly necessary for his/her role.
Why it is important to measure it ?
This indicator provides information on the staff to be hired for the management of the faecal sludge treatment site.
Definition of indicator
This indicator is required to know how much sludge is currently really treated at the faecal sludge treatment site.
How to measure or calculate it ?
Calculate the real input flow by measuring the sludge volume in transport tanks to the faecal sludge treatment site or by measuring the pumps flow rates and their time of use during desludging. Consider an average value including also the days the faecal sludge treatment activities don’t run.
Why it is important to measure it ?
When the real input flow is known, it’s possible to compare it with design input flow and with the output sludge production and give important indications about possible upgrading.
Definition of indicator
This indicator defines how much sludge is produced daily by the faecal sludge treatment site in comparison to real input flow for an average operational period
How to measure or calculate it ?
Measure weight of the sludge produced daily before disposal or reuse out of the sludge treatment site. Divide it by real input flow (see indicator). Consider an average value including also the days faecal sludge treatment activities don’t run.
References, tips, examples
Output sludge production in comparison to sludge input flow can vary a lot according to treatment processes:
Chemical treatment like lime where the volume of sludge does not change (volume sludge in = volume sludge out);
Physical and biological treatment (separation of solids from fluids, aerobic or anaerobic digestion of sludge). Here the volume of sludge decreases drastically to 5-15% of the original volume (see examples).
Why it is important to measure it ?
The volume of sludge is an important parameter in sizing the transportation and disposal system of processed sludge from the faecal sludge treatment site.
Definition of indicator
Biochemical Oxygen Demand (BOD, also called Biological Oxygen Demand) is the amount of dissolved oxygen needed (i.e. demanded) by aerobic biological organisms to break down organic material present in a given water sample at certain temperature over a specific time period. The BOD value is most commonly expressed in milligrams of oxygen consumed per litre of sample during 5 days of incubation at 20 °C (mg/L).
The reduction is related to the BOD of effluent exiting the faecal sludge treatment site in comparison to the BOD of influent entering the faecal sludge treatment site.
How to measure or calculate it ?
The reduction is calculated as COMPLEMENTARY PERCENTAGE of the average BOD of effluent exiting the faecal sludge treatment site over the average BOD of influent entering the faecal sludge treatment site in the same period.
References, tips, examples
The laboratory test protocol can be seen at:
The STeP Global Testing Protocols & Parameters – A best practices guide for testing sanitation technologies in the field
http://stepsforsanitation.org/?smd_process_download=1&download_id=4171
Influent example from Zambia: 25,000-40,000mg/l for pit latrines and 1,000-2,000mg/l for septic tanks
maximum concentration example of liquid effluent as per the ZEMA standard 50mg/l.
Why it is important to measure it ?
Faecal sludge characteristics vary widely between cities, types of on site sanitation systems and type of emptying system used. Even samples taken from the same pit latrine.
Definition of indicator
Chemical oxygen demand (COD) is an indicative measure of the amount of oxygen that can be consumed by reactions in a measured solution. It is commonly expressed in mass of oxygen consumed over volume of solution (mg/L).
The reduction is related to the COD of effluent exiting the faecal sludge treatment site in comparison to the COD of influent entering the faecal sludge treatment site.
How to measure or calculate it ?
The reduction is calculated as COMPLEMENTARY PERCENTAGE of the average COD of effluent exiting the faecal sludge treatment site over the average COD of influent entering the faecal sludge treatment site in the same period.
References, tips, examples
The laboratory test protocol can be seen at:
The STeP Global Testing Protocols & Parameters – A best practices guide for testing sanitation technologies in the field
http://stepsforsanitation.org/?smd_process_download=1&download_id=4171
Influent example from Zambia: 50,000-100,000mg/l for pit latrines and 10,000-20,000mg/l for septic tanks
maximum concentration example of liquid effluent as per the ZEMA standard 50mg/l.
Why it is important to measure it ?
Faecal sludge characteristics vary widely between cities, types of on site sanitation systems and type of emptying system used. Even samples taken from the same pit latrine have been shown to have significant variation in standard physio-chemical testing. Such characteristics impact how sludge can be processed following removal. Stabilised sludge is very poor in terms of gas release in an anaerobic digester.
Definition of indicator
Faecal coliforms are facultatively anaerobic, rod-shaped, gram-negative, non-sporulating bacterium. Coliform bacteria generally originate in the intestines of warm-blooded animals. Faecal coliforms are capable of growth in the presence of bile salts or similar surface agents, are oxidase negative, and produce acid and gas from lactose within 48 hours at 44 ± 0.5°C.The term “thermotolerant coliform” is more correct and is gaining acceptance over “faecal coliform”.
Coliform bacteria include genera that originate in feces (e.g. Escherichia) as well as genera not of faecal origin (e.g. Enterobacter, Klebsiella, Citrobacter). The assay is intended to be an indicator of faecal contamination; more specifically of E. coli which is an indicator microorganism for other pathogens that may be present in feces. They are commonly expressed in colony forming units over 100mL volume of solution (CFU/100mL).
The reduction is related to the faecal coliforms of effluent exiting the faecal sludge treatment site in comparison to the faecal coliforms of influent entering the faecal sludge treatment site.
How to measure or calculate it ?
The reduction is calculated as COMPLEMENTARY PERCENTAGE of the average faecal coliforms of effluent exiting the faecal sludge treatment site over the average faecal coliforms of influent entering the faecal sludge treatment site in the same period.
References, tips, examples
The laboratory test protocol can be seen at:
The STeP Global Testing Protocols & Parameters – A best practices guide for testing sanitation technologies in the field
http://stepsforsanitation.org/?smd_process_download=1&download_id=4171
Influent example from Zambia: 2*107 CFU/100ml for pit latrines and 1*105 CFU/100ml for septic tanks
maximum concentration example of liquid effluent as per the ZEMA standard 2500CFU/100ml.
Why it is important to measure it ?
Faecal sludge characteristics varies widely between cities, types of on site sanitation systems and type of emptying system used. Even samples taken from the same pit latrine have been shown to have significant variation in standard physio-chemical testing. Such characteristics impact how sludge can be processed following removal. Stabilised sludge is very poor in terms of gas release in an anaerobic digester.
Definition of indicator
Total solids are the total dissolved solids (TDS) + total suspended solids (TSS). They are commonly expressed as mass of solids in comparison to volume of solution (% weight-volume).
The reduction is related to the total solids of effluent exiting the faecal sludge treatment site in comparison to the total solids of influent entering the faecal sludge treatment site.
How to measure or calculate it ?
The reduction is calculated as COMPLEMENTARY PERCENTAGE of the average total solids of effluent exiting the faecal sludge treatment site over the average total solids of influent entering the faecal sludge treatment site in the same period.
References, tips, examples
The laboratory test protocol can be seen at:
The STeP Global Testing Protocols & Parameters – A best practices guide for testing sanitation technologies in the field
http://stepsforsanitation.org/?smd_process_download=1&download_id=4171
Septage (contents of a septic tank) is much easier to pump and treat due to the low % of solids (typically 1-2 %) than faecal sludge from pit latrines with a high % of solids (typically 10-15%). Solids content is an important parameter to estimate the volume of dried sludge to be removed from the drying beds of sludge treatment plants. After 2 weeks drying period the typical solids content is 40% dry solids. Hence, 1 m3 (1,000 litres) of septage containing 1% of dry solids has been decreased to 1,000 *1%/(40%) = 25 kg of biosolids. The remainder (typically 1,000-25 = 975 litres has partially evaporated, partially drained away. The drainage water, say max 975 litres, needs to be treated in a filter / pond system. Also, 1 m3 (1,000 litres) of faecal sludge containing 15% of dry solids has been decreased to 1,000 *15%/(40%) = 375 kg of biosolids. The remainder (typically 1,000-375 = 625 litres has partially evaporated, partially drained away. The drainage water, say max 625 litres, needs to be treated in a filter / pond system;
Influent example from Zambia: 7-15% for pit latrines and 1-2% for septic tanks.
Why it is important to measure it ?
Faecal sludge characteristics vary widely between cities, types of on site sanitation systems and type of emptying system used. Even samples taken from the same pit latrine have been shown to have significant variation in standard physio-chemical testing. Such characteristics impact how sludge can be processed following removal. Stabilised sludge is very poor in terms of gas release in an anaerobic digester.
Solids content is an important parameter to estimate the volume of dried sludge to be removed from the drying beds of sludge treatment plants.
Definition of indicator
pH is a logarithmic scale used to specify the acidity or basicity of an aqueous solution. It is approximately the negative of the base 10 logarithm of the molar concentration, measured in units of moles per litre, of hydrogen ions. Indeed it doesn’t have unit measure.
The variation is related to the pH of effluent exiting the faecal sludge treatment site in comparison to the pH of influent entering the faecal sludge treatment site.
How to measure or calculate it ?
The variation is calculated as positive (when effluent pH is higher than influent pH) or negative (when effluent pH is lower than influent pH) difference of the average pH of effluent exiting the faecal sludge treatment site in comparison to the average pH of influent entering the faecal sludge treatment site in the same period.
References, tips, examples
The laboratory test protocol can be seen at:
The STeP Global Testing Protocols & Parameters – A best practices guide for testing sanitation technologies in the field
http://stepsforsanitation.org/?smd_process_download=1&download_id=4171
Influent example from Zambia: 7.5-7.8 for pit latrines and 7.0-7.5 for septic tanks
Example range of liquid effluent as per the ZEMA standard 6-9.
Why it is important to measure it ?
Faecal sludge characteristics vary widely between cities, types of on site sanitation systems and type of emptying system used. Even samples taken from the same pit latrine have been shown to have significant variation in standard physio-chemical testing. Such characteristics impact how sludge can be processed following removal. Stabilised sludge is very poor in terms of gas release in an anaerobic digester.
Definition of indicator
Parasitic worms, also known as helminths, are large macroparasites, which as adults can generally be seen with the naked eye. Many are intestinal worms that are soil-transmitted and infect the gastrointestinal tract. It is an umbrella term that includes many species of worm from different genera. Helminth eggs of concern in wastewater used for irrigation have a size between 20 and 90 μm. They are commonly expressed in number of eggs per gram of solution (n/g).
The reduction is related to the Helminth eggs in the effluent exiting the faecal sludge treatment site in comparison to the Helminth eggs in the influent entering the faecal sludge treatment site.
How to measure or calculate it ?
The reduction is calculated as COMPLEMENTARY PERCENTAGE of the average Helminths eggs in the effluent exiting the faecal sludge treatment site over the average Helminth eggs in the influent entering the faecal sludge treatment site in the same period.
References, tips, examples
The laboratory test protocol can be seen at:
The STeP Global Testing Protocols & Parameters – A best practices guide for testing sanitation technologies in the field
http://stepsforsanitation.org/?smd_process_download=1&download_id=4171
It is very difficult to inactivate helminth eggs, unless temperature is increased above 40 °C or moisture is reduced to less than 5%.
Why it is important to measure it ?
Helminth eggs (or ova) are a good indicator organism to assess the safety of sanitation reuse systems for resource recovery because they are the most environmentally resistant faecal pathogens and they can in extreme cases survive for several years in soil.
Definition of indicator
The indicator defines if the faecal sludge treatment system is operated exclusively by the beneficiary community without any constant external support.
How to measure or calculate it ?
Analyse responsibilities and tasks of the faecal sludge treatment site management. Identify if they are all cover by the beneficiary community or part of it. If there is occasional external support, still consider that the site is completely operated by the community.
Why it is important to measure it ?
It is important to know the complexity of operations in relation to the skills of the community in order to plan the faecal treatment site management and forecast long-term sustainability.
Definition of indicator
The indicator defines if washing capacities are available for the faecal sludge treatment workers.
How to measure or calculate it ?
Analyse if washing capacity (with adequate privacy and supplied with enough water and soap/chlore) are available and accessible at the key moments (before eating or drinking and before leaving the faecal sludge treatment site).
Why it is important to measure it ?
Washing capacity is key to protect the health of faecal sludge treatment workers and their family.
Definition of indicator
The indicator defines if Personal Protection Equipment (PPEs) are available for the faecal sludge treatment workers and potential visitors.
How to measure or calculate it ?
Analyse if Personal Protection Equipment (PPE) are available, accessible and frequently washed or replaced.
Why it is important to measure it ?
PPEs are key to protect the health of faecal sludge treatment workers and their family.
Definition of indicator
This indicator defines the level of knowledge and experience required to be able to upgrade or decommission the faecal sludge treatment site successfully.
How to measure or calculate it ?
The indicator is determined by forecasting an eventual upgrading or decommissioning phase taking lessons learnt from the construction process (including selection of contractors or construction staff). Should specific contractors and specialists be involved for special supervision, know-how, equipment?
Why it is important to measure it ?
Faecal sludge is a potential dangerous material: a simple mistake in infrastructures construction may stop operations for several weeks and affect the sustainability of faecal sludge treatment. For the same reason, decommissioning and disposal of faecal sludge treatment infrastructures and equipment can contaminate the environment and affect population living around the disposal site or dismissed faecal sludge treatment site.
Definition of the indicator
This indicates if the knowledge and experience level of an FSM specialist is required to be able to design, contruct, operate and maintain the faecal sludge treatment site successfully.
Communitarian operation means the faecal sludge treatment system is operated exclusively by the beneficiary community without constant external support.
Unit/value:
FSM specialist for design
FSM specialist for construction
FSM specialist for operation and maintenance
Communitarian operation
How to measure or calculate it
For design: the indicator is determined by assessing the design process and understanding if specialists were involved or not.
For construction: the indicator is determined by assessing the construction process (including selection of contractors or construction staff) and understanding if specific contractors and specialists for special supervision, know-how, equipment use were involved or not.
For operation and maintenance: analyse the CV of the manager of the O&M of the faecal sludge treatment site and identify if he/she has completed higher education related to FSM and if this education is strictly necessary for his/her role.
For community operation: analyse responsibilities and tasks of the faecal sludge treatment site management. Identify if they are covered by the beneficiary community. If there is occasional external support, still consider that the site is completely operated by the community.
References, tips, examples
Example of different design skills in the same context: the design of Oxfam’s large scale faecal sludge treatment site in Cox’s Bazaar was implemented in collaboration with Borda (sanitation experts); Oxfam’s small lime stabilization faecal treatment site was implemented by WASH officers (not FSM specialists).
Why is it important to measure it
This indicator is important to know what kind of skills are needed to have a properly functioning treatment plant, to be able to hire the right people for the task and to select the technologies according to the local skills available.
Définition de l’indicateur
L’indicateur précise si la zone où se situe le site de traitement de boues de vidange est sujette aux inondations.
Comment le mesurer ou le calculer ?
En vous appuyant sur la documentation et les connaissances locales, vérifiez à quand remonte la dernière inondation du site de traitement de boues de vidange. L’indicateur précise si la zone où se situe le site de traitement a déjà été inondée pendant une période antérieure égale à la durée de vie du projet (voir indicateur) et si rien n’a été fait pour éviter les inondations dans la zone pendant la construction. L’indicateur prend en considération uniquement le site de traitement de boues de vidange, sans tenir compte des routes d’accès ou des latrines.
Pourquoi c’est important de le mesurer
Les boues de vidange sont des matières potentiellement dangereuses : les inondations peuvent provoquer l’arrêt de l’exploitation pendant plusieurs semaines et/ou répandre la contamination fécale en dehors du site de traitement de boues de vidange.
Définition de l’indicateur
La Demande Biochimique en Oxygène (DBO) est la quantité d’oxygène dissoute requise (c.-à-d. exigée) par les organismes biologiques aérobies pour pouvoir décomposer les matières organiques présentes dans un échantillon d’eau donné à une certaine température pendant une période de temps spécifique. La valeur de la DBO s’exprime le plus souvent en milligrammes d’oxygène consommés par litre d’échantillon pendant 5 jours d’incubation à 20°C (mg/l).
La réduction fait référence à la DBO de l’effluent sortant du site de traitement de boues de vidange par rapport à la DBO de l’influent entrant dans le site de traitement de boues de vidange.
Comment le mesurer ou le calculer ?
TLa réduction se calcule comme un POURCENTAGE COMPLÉMENTAIRE de la DBO moyenne de l’effluent sortant du site de traitement de boues de vidange, divisé par la DBO moyenne de l’influent entrant dans le site de traitement de boues de vidange pendant la même période.
Pourquoi c’est important de le mesurer
Les caractéristiques des boues de vidange varient beaucoup selon la ville de provenance, le type de système d’assainissement sur place et le système de vidange utilisé. Dans des échantillons issus de la fosse d’une seule latrine, on a même constaté des variations significatives lors des analyses physico-chimiques standards. La DBO dans les latrines à fosse peut baisser avec la profondeur (avec l’augmentation de l’âge des boues), ce qui démontre une stabilité croissante des boues et donc une diminution de la dégradation microbienne. De tels caractéristiques influent sur la méthode de traitement des boues après leur enlèvement. Les boues stabilisées ont un rendement très faible de gaz dans un digesteur anaérobie.
Définition de l’indicateur
La Demande Chimique en Oxygène (DCO) sert à mesurer, à titre indicatif, la quantité d’oxygène qui peut être consommée par des réactions dans une quantité de solution donnée. Elle s’exprime généralement en masse d’oxygène consommée par rapport au volume de solution (mg/l).
La réduction fait référence à la DCO de l’effluent sortant du site de traitement de boues de vidange par rapport à la DCO de l’influent entrant dans le site de traitement de boues de vidange.
Comment le mesurer ou le calculer ?
La réduction se calcule comme un POURCENTAGE COMPLÉMENTAIRE de la DCO moyenne de l’effluent sortant du site de traitement de boues de vidange, divisé par la DCO moyenne de l’influent entrant dans le site de traitement de boues de vidange pendant la même période.
Pourquoi c’est important de le mesurer
Les caractéristiques des boues de vidange varient beaucoup selon la ville de provenance, le type de système d’assainissement sur place et le système de vidange utilisé. Dans des échantillons issus de la fosse d’une seule latrine, on a même constaté des variations significatives lors des analyses physico-chimiques standards. De tels caractéristiques influent sur la méthode de traitement des boues après leur enlèvement. Les boues stabilisées ont un rendement très faible de gaz dans un digesteur anaérobie.
Définition de l’indicateur
Cet indicateur précise si le système de traitement de boues de vidange est gérée exclusivement par la communauté bénéficiaire sans aucun soutien extérieur régulier.
Comment le mesurer ou le calculer ?
Étudiez les tâches et les responsabilités liées à la gestion du site de traitement de boues de vidange. Déterminez si elles sont toutes couvertes par la communauté bénéficiaire ou une partie de celle-ci. Si on fait appel à des soutiens extérieurs ponctuels, il faut néanmoins considérer que le site est entièrement géré par la communauté.
Pourquoi c’est important de le mesurer
Il est important de reconnaître la complexité des opérations par rapport aux compétences de la communauté afin de planifier la gestion du site de traitement de boues de vidange et de prévoir la pérennité du projet dans la durée.
Définition de l’indicateur
Cet indicateur désigne le total des coûts suivants :
– Dépenses préliminaires et générales (entreprises de transport/services généraux et supervision, sécurité, assurance, connexion à l’alimentation électrique, etc.)
– Travaux de génie civil
– Travaux électromécaniques : pompes, GenSet (group électrogène)
– Conception (en général, 5 % des coûts électromécaniques et de génie civile)
– Supervision de la mise en œuvre (en général, 5-15 % des coûts électromécaniques et de génie civile)
divisé par le flux actuel.
Comment le mesurer ou le calculer ?
Tous les investissements nécessaires pour construire et mettre en place le système de traitement de boues de vidange (HORS L’ACHAT DE TERRAIN) doivent être pris en compte et divisés par le flux entrant réel (voir indicateur). Cela inclut également une part des ressources humaines impliquées dans la conception et la construction, qui peuvent également effectuer d’autres tâches.
Pourquoi c’est important de le mesurer
Le ratio des dépenses d’investissement au flux actuel pour un site de traitement de boues de vidange sera différent d’un endroit à un autre, essentiellement en fonction des coûts de transport.
Définition de l’indicateur
Cet indicateur désigne le total des coûts suivants :
– Dépenses préliminaires et générales (entreprises de transport/services généraux et supervision, sécurité, assurance, connexion à l’alimentation électrique, etc.)
– Achat de terrain
– Travaux de génie civil
– Travaux électromécaniques : pompes, GenSet (group électrogène)
– Conception (en général, 5 % des coûts électromécaniques et de génie civile)
– Supervision de la mise en œuvre (en général, 5-15 % des coûts électromécaniques et de génie civile)
divisé par le flux actuel.
Comment le mesurer ou le calculer ?
Tous les investissements nécessaires pour construire et mettre en place le système de traitement de boues de vidange doivent être pris en compte et divisés par le flux entrant réel (voir indicateur). Cela inclut également une part des ressources humaines impliquées dans la conception et la construction, qui peuvent également effectuer d’autres tâches.
Pourquoi c’est important de le mesurer
Le ratio des dépenses d’investissement au flux actuel pour un site de traitement de boues de vidange sera différent d’un endroit à un autre, essentiellement en fonction des coûts de transport.
Définition de l’indicateur
Nombre de personnes pouvant bénéficier du service de traitement de boues de vidange.
Comment le mesurer ou le calculer ?
Etudiez la population actuelle et ses tendances de croissance et de déplacement. A l’intérieur d’une population stable croissante, la population à desservir peut être calculée de la manière suivante :
Pn = P0 * (1 + i)^n
Pn = la population en année ‘n’ (consulter l’indicateur de durée de vie)
n = la période d’exploitation prévue
P0 = la population en année 0
i = la croissance annuelle de la population
Par contre, dans un contexte humanitaire, ce chiffre a tendance à évoluer selon le contexte de sécurité (estimation de la population affectée par une catastrophe naturelle/d’origine humaine).
Pourquoi c’est important de le mesurer
Lorsqu’on connaît la population, on dispose d’une base solide pour dimensionner le site de traitement : dimensionnement des réservoirs ET dimensionnement des éventuels pompes, lits de séchage, etc.
Définition de l’indicateur
Cet indicateur précise le flux de boues pour lequel le site de traitement a été conçu.
Comment le mesurer ou le calculer ?
Si possible, passez en revue le document de calcul du projet et demandez conseil à l’équipe ou aux consultants en charge de la conception. Le flux entrant aurait dû être pris en considération pour dimensionner le projet. De manière générale, si ce n’est pas possible de le mesurer sur le terrain, on estime le flux entrant de la manière suivante :
Pour des latrines à fosse simples en contexte d’urgence, vidangées à intervalles régulières avec peu d’infiltration dans le sol : on estime 2,2 l/p/j (1 l pour le nettoyage anal et le nettoyage des toilettes + 1,2 l de fèces),
Pour des fosses simples en contexte d’urgence où l’effluent peut s’infiltrer, vidangées à intervalles régulières, il faut envisager les taux d’accumulation de boues suivants :
Déchets résiduels dans l’eau lorsque l’eau est utilisée pour le nettoyage anal : 25 litres par personne par année (l/p/a) ;
Déchets résiduels dans l’eau lorsque des matières biodégradables sont utilisées pour le nettoyage anal : 40 l/p/a ;
Déchets résiduels dans l’eau lorsque des matières non-biodégradables sont utilisées pour le nettoyage anal : 60 l/p/a ;
Déchets résiduels en milieu sec lorsque des matières biodégradables sont utilisées pour le nettoyage anal : 60 l/p/a ;
Déchets résiduels en milieu sec lorsque des matières non-biodégradables sont utilisées pour le nettoyage anal : 90 l/p/a ;
Pour des installations à chasse d’eau manuelle où l’eau ne peut s’infiltrer, vidangées à intervalles régulières, on estime 4,2 l/p/j (2 l pour l’eau de chasse additionnelle),
Pour les petits réseaux (égouts de faible diamètre, égouts sans matières solides) et lorsqu’il y a également un réseau d’eau potable domestique : on estime que 80% de l’eau potable distribuée se retrouve dans le système d’assainissement.
Dans certaines conditions environnementales et pour certaines infrastructures, on doit tenir compte de l’infiltration des eaux souterraines à l’intérieur des installations d’assainissement.
Pourquoi c’est important de le mesurer
Lorsqu’on connaît le flux entrant consideré pour la conception, on dispose d’une base solide pour dimensionner le site de traitement : dimensionnement des réservoirs ET dimensionnement des éventuels pompes, lits de séchage, etc. La quantité de boues peut largement excéder le volume d’urines et de fèces, ce qui aura un impact important sur le dimensionnement. Si on néglige cet aspect, les infrastructures seront trop petites, ce qui raccourcira les temps de rétention/traitement et produira des résultats médiocres.
Définition de l’indicateur
Les coliformes fécaux sont des bactéries anaérobies facultatives, de forme allongée, non-sporulantes, à Gram négatif. Les bactéries coliformes proviennent généralement des intestins des animaux à sang chaud. Les coliformes fécaux sont capables de se développer en présence de sels biliaires ou d’autres tensioactifs similaires. Ils sont oxydase négative et fermentent le lactose avec production d’acide et de gaz à 44 ± 0,5°C en 48 heures. Le terme ‘coliforme thermotolérant’, plus exact, gagne progressivement du terrain sur ‘coliforme fécal’.
Les bactéries coliformes comprennent des genera provenant des fèces (ex. Escherichia) ainsi que des genera qui ne sont pas d’origine fécale (ex. Enterobacter, Klebsiella, Citrobacter). L’analyse vise à indiquer une contamination fécale ; en particulier par E. coli, un micro-organisme indicateur d’autres pathogènes pouvant être présents dans les fèces. Les coliformes fécaux s’expriment généralement en unités formant des colonies (UFC) par rapport à 100 ml de solution (UFC/100 ml).
La réduction fait référence aux coliformes fécaux présents dans l’effluent sortant du site de traitement de boues de vidange par rapport aux coliformes fécaux présents dans l’influent entrant dans le site de traitement de boues de vidange.
Comment le mesurer ou le calculer ?
La réduction se calcule comme un POURCENTAGE COMPLÉMENTAIRE de la moyenne des coliformes fécaux dans l’effluent sortant du site de traitement de boues de vidange, divisé par la moyenne des coliformes fécaux dans l’influent entrant dans le site de traitement de boues de vidange pendant la même période.
Pourquoi c’est important de le mesurer
Les caractéristiques des boues de vidange varient beaucoup selon la ville de provenance, le type de système d’assainissement sur place et le système de vidange utilisé. Dans des échantillons issus de la fosse d’une seule latrine, on a même constaté des variations significatives lors des analyses physico-chimiques standards. De tels caractéristiques influent sur la méthode de traitement des boues après leur enlèvement. Les boues stabilisées ont un rendement très faible de gaz dans un digesteur anaérobie.
Définition de l’indicateur
Cet indicateur précise la durée prévue de fonctionnement du site de traitement de boues de vidange au moment de sa conception.
Comment le mesurer ou le calculer ?
Définissez les besoins immédiats et à long terme. Étudiez les tendances de croissance et de déplacement de la population (voir l’indicateur de population bénéficiaire considérée pour la conception), ainsi que les engagements des donateurs et des acteurs impliqués à l’avenir.
Pourquoi c’est important de le mesurer
Il est important de connaître la période d’exploitation prévue pour aider à calculer la population bénéficiaire considérée pour la conception (voir indicateur) du site de traitement de boues de vidange. En outre, il est important de connaître la durée de vie requise du site de traitement afin de choisir des matériaux de construction appropriés.
Définition de l’indicateur
Les matériaux disponibles sur place sont des matériaux qui n’ont pas besoin d’être importés.
Comment le mesurer ou le calculer ?
Vérifiez si une clôture a été installée sur tout le périmètre du site de traitement de boues de vidange. Identifiez les points faibles où des personnes, animaux ou véhicules non impliqués dans le processus de traitement pourraient entrer sur le site.
Pourquoi c’est important de le mesurer
Une clôture adéquate est obligatoire en toutes circonstances, ainsi que la présence d’agents de sécurité 24 h sur 24 : les boues de fosses septiques, les eaux usées et les boues de vidange sont des matières dangereuses qui peuvent facilement être utilisées pour contaminer une communauté entière. Pensez au vandalisme en perçant un trou dans un réservoir souple plein de boues.
Definition of the indicator
Operation expenditure includes the daily average of:
– Staff costs
– Energy costs (especially high when electricity needs to be generated separately)
– Chemical costs
– Transport costs
– Administration costs
– Water for cleaning / operating costs
– Personal Protection Equipment costs
– Etc.
divided by real input flow.
This doesn’t include the desludging costs.
Unit/value: USD/m3
How to measure or calculate it
Review the operation and maintenance SOPs, the purchase documents and ask the staff. All the expenditure for operation has to be considered and divided by the real input flow (see indicator). Expenditure for daily, weekly and monthly operation, as well as yearly and extraordinary maintenance should be considered as a daily average. It includes the cost of human resources involved in the operation and maintenance of the plant, but it doesn’t include the costs related to desludging activities.
References, tips, examples
Typical O&M costs for faecal sludge treatment plants around the world are 6-10 USD/m3.
Why is it important to measure it
This indicator is useful to know the economical efficiency of a faecal sludge treatment system.
Définition de l’indicateur
Dans ce cas, l’objectif est le traitement ou la modification souhaité des boues entrantes, avant leur élimination ou réutilisation.
Comment le mesurer ou le calculer ?
Si possible, passez en revue le document de conception et demandez conseil à l’équipe de consultants en charge de la conception: l’objectif aurait dû être pris en considération pour concevoir et dimensionner le site de traitement de boues de vidange. De manière générale, l’objectif fait référence à la qualité des boues entrantes et aux conditions environnementales des sites d’élimination ou à la méthodologie de réutilisation souhaitée.
Pourquoi c’est important de le mesurer
C’est très important pour concevoir le site de traitement de boues de vidange et pour évaluer l’efficacité du traitement.
Définition de l’indicateur
Cet indicateur est nécessaire pour connaître le volume réel de boues traitées actuellement au site de traitement de boues de vidange.
Comment le mesurer ou le calculer ?
Calculez le flux entrant réel soit en mesurant le volume de boues dans les citernes transportées vers le site de traitement, soit en mesurant le débit des pompes et leur temps de fonctionnement pendant le vidange des boues. Prenez une valeur moyenne qui tient également compte des jours d’inactivité du site de traitement de boues de vidange.
Pourquoi c’est important de le mesurer
Lorsqu’on connaît le flux entrant réel, on peut le comparer avec le flux entrant considéré pour la conception et la production de boues sortant pour donner des indications importantes sur une mise à niveau éventuelle.
Définition de l’indicateur
Il s’agit de la surface occupée par le site de traitement de boues de vidange par rapport à la population considérée pour la conception (voir indicateur).
Comment le mesurer ou le calculer ?
Mesurez, soit sur le terrain, soit au niveau des plans du projet, la superficie totale du site de traitement de boues de vidange et divisez-le par la population considérée pour la conception (voir indicateur).
Pourquoi c’est important de le mesurer
Dans un contexte humanitaire, les populations sont souvent obligées de s’installer dans des zones surpeuplées où les conditions environnementales sont défavorables. Cela impacte également l’espace disponible pour des sites de traitement de boues de vidange et des infrastructures d’assainissement en général.
Définition de l’indicateur
Cet indicateur précise le niveau de connaissances et d’expérience nécessaires pour mener à bien la construction d’un site de traitement de boues de vidange.
Comment le mesurer ou le calculer ?
On obtient cet indicateur en évaluant le déroulement de la construction (y compris la sélection des entreprises ou du personnel de construction) pour déterminer si on a fait appel ou non à des entreprises spécifiques ou à des spécialistes pour apporter une supervision, des savoir-faire ou des équipements particuliers.
Pourquoi c’est important de le mesurer
Les boues de vidange sont des matières potentiellement dangereuses : une simple erreur dans la construction des infrastructures peut provoquer l’arrêt de l’exploitation pendant plusieurs semaines et influer sur la pérennité du traitement des boues de vidange.
Définition de l’indicateur
Cet indicateur précise le type d’infrastructure d’assainissement d’où proviennent les boues.
Comment le mesurer ou le calculer ?
S’ils existent, étudiez les rapports de vidange de boues où ces informations sont enregistrées. Sinon, observez les activités de vidange de boues et les infrastructures d’assainissement d’où proviennent les boues. Parlez avec les personnes responsables de la vidange de boues.
Pourquoi c’est important de le mesurer
Il est important de connaître la provenance des boues pour pouvoir évaluer leurs caractéristiques et déterminer la probabilité qu’elles soient contaminées par des pathogènes (bien entendu toutes les boues de vidange doivent être traitées comme des matières dangereuses mais les déchets hospitaliers risquent d’être encore plus dangereux et nécessitent une attention particulière).
Définition de l’indicateur
Les Matières Sèches (MS) regroupent les Solides Dissous Totaux (SDT) + les Matières En Suspension (MES). Elles s’expriment généralement en masse de matières solides par rapport au volume de solution (% poids-volume).
La réduction fait référence aux matières sèches dans l’effluent sortant du site de traitement de boues de vidange par rapport aux matières sèches dans l’influent entrant dans le site de traitement de boues de vidange.
Comment le mesurer ou le calculer ?
La réduction se calcule comme un POURCENTAGE COMPLÉMENTAIRE de la moyenne des matières sèches dans l’effluent sortant du site de traitement de boues de vidange, divisé par la moyenne des matières sèches dans l’influent entrant dans le site de traitement de boues de vidange pendant la même période.
Pourquoi c’est important de le mesurer
Les caractéristiques des boues de vidange varient beaucoup selon la ville de provenance, le type de système d’assainissement sur place et le système de vidange utilisé. Dans des échantillons issus de la fosse d’une seule latrine, on a même constaté des variations significatives lors des analyses physico-chimiques standards. De tels caractéristiques influent sur la méthode de traitement des boues après leur enlèvement. Les boues stabilisées ont un rendement très faible de gaz dans un digesteur anaérobie.
La teneur en substance solide est un paramètre important pour estimer le volume de boues séchées qu’il faudra enlever des lits de séchage des stations de traitement de boues.
Définition de l’indicateur
Cet indicateur précise si les principaux produits issus du site de traitement de boues de vidange se composent uniquement de boues, d’effluent, ou des deux.
Comment le mesurer ou le calculer ?
Observez si on peut distinguer deux produits différents suite aux mécanismes de séparation des matières solides/liquides, en se basant sur leur densité et leur teneur en substance solide.
Pourquoi c’est important de le mesurer
Savoir s’il y a des produits sortants différents permet de prévoir la création de chaînes de traitement et de mécanismes d’élimination spécifiques et différenciés.
