Fecal sludge management (FSM) (or faecal sludge management in British English) is the storage, collection, transport, treatment and safe end use or disposal of fecal sludge.
Together, the collection, transport, treatment and end use of fecal sludge constitute the "value chain" or "service chain" of fecal sludge management. Fecal sludge is defined very broadly as what accumulates in
onsite sanitation
Sanitation refers to public health conditions related to clean drinking water and treatment and disposal of human excreta and sewage. Preventing human contact with feces is part of sanitation, as is hand washing with soap. Sanitation systems ...
systems (e.g.
pit latrine
A pit latrine, also known as pit toilet, is a type of toilet that collects human feces in a hole in the ground. Urine and feces enter the pit through a drop hole in the floor, which might be connected to a toilet seat or squatting pan for use ...
s,
septic tank
A septic tank is an underground chamber made of concrete, fiberglass, or plastic through which domestic wastewater ( sewage) flows for basic sewage treatment. Settling and anaerobic digestion processes reduce solids and organics, but the treatm ...
s and
container-based solutions) and specifically is not transported through a
sewer. It is composed of
human excreta
Human waste (or human excreta) refers to the waste products of the human digestive system, menses, and human metabolism including urine and faeces. As part of a sanitation system that is in place, human waste is collected, transported, treated a ...
, but also anything else that may go into an onsite containment technology, such as flushwater, cleansing materials (e.g.
toilet paper
Toilet paper (sometimes called toilet tissue or bathroom tissue) is a tissue paper product primarily used to clean the anus and surrounding anal region of feces after defecation, and to clean the perineal area and external genitalia of ur ...
and
anal cleansing
Anal hygiene or anal cleansing refers to hygienic practices that are performed on a person's anus, usually shortly after defecation. Post-defecation cleansing is rarely discussed academically, partly due to the social taboo. The scientific objec ...
materials),
menstrual hygiene
Feminine hygiene products are personal care products used during menstruation, vaginal discharge, and other bodily functions related to the vulva and vagina. Products that are used during menstruation may also be called menstrual hygiene product ...
products, grey water (i.e. bathing or kitchen water, including fats, oils and grease), and
solid waste. Fecal sludge that is removed from septic tanks is called septage.
It is estimated that one-third of the world’s population is served by onsite sanitation, and that in low-income countries less than 10% of urban areas are served by sewers. In low-income countries, the majority of fecal sludge is discharged untreated into the urban environment, placing a huge burden on public and environmental health. Hence, FSM plays a critical role in safely managed sanitation and the protection of
public health
Public health is "the science and art of preventing disease, prolonging life and promoting health through the organized efforts and informed choices of society, organizations, public and private, communities and individuals". Analyzing the det ...
. FSM services are provided by a range of formal and informal private sector services providers, local governments, water authorities, and
public utilities
A public utility company (usually just utility) is an organization that maintains the infrastructure for a public service (often also providing a service using that infrastructure). Public utilities are subject to forms of public control and ...
. This can also result in unreliable services with relatively high costs at the household level.
Fecal sludge collection can be arranged on a scheduled basis or on a call-for-service basis (also known as on-demand, on-request, or non-scheduled services). The collected fecal sludge may be manually or mechanically emptied, and then transported to treatment plants with a
vacuum truck
A vacuum truck, vacuum tanker, vactor truck, or vactor is a tank truck that has a pump and a tank. The pump is designed to pneumatically suck liquids, sludges, slurries, or the like from a location (often underground) into the tank of the truc ...
; a tank and pump mounted on a flatbed truck; a small tank pulled by a motorcycle; or in containers on a handcart. The wider use of multiple decentralized sludge treatment facilities within cities (to avoid long haulage distances) is currently being researched and piloted.
Fecal sludge is different to
wastewater
Wastewater is water generated after the use of freshwater, raw water, drinking water or saline water in a variety of deliberate applications or processes. Another definition of wastewater is "Used water from any combination of domestic, industrial ...
and cannot simply be co-treated at
sewage treatment
Sewage treatment (or domestic wastewater treatment, municipal wastewater treatment) is a type of wastewater treatment which aims to remove contaminants from sewage to produce an effluent that is suitable for discharge to the surrounding e ...
plants. Small additions of fecal sludge are possible if plants are underutilized and able to take the additional load, and facilities to separate liquids and solids are available.
[Strande, L., Ronteltap, M., Brdjanovic, D. (eds.) (2014)]
Faecal Sludge Management (FSM) book - Systems Approach for Implementation and Operation
IWA Publishing, UK () A variety of mechanized and non-mechanized processing technologies may be used, including
settling tanks, planted and unplanted drying beds, and
waste stabilization ponds. The treatment process can produce
resource recovery
Resource recovery is using wastes as an input material to create valuable products as new outputs. The aim is to reduce the amount of waste generated, thereby reducing the need for landfill space, and optimising the values created from waste. Reso ...
end-products such as treated
effluent that can be used for
irrigation
Irrigation (also referred to as watering) is the practice of applying controlled amounts of water to land to help grow Crop, crops, Landscape plant, landscape plants, and Lawn, lawns. Irrigation has been a key aspect of agriculture for over 5,00 ...
, co-
composting
Compost is a mixture of ingredients used as plant fertilizer and to improve soil's physical, chemical and biological properties. It is commonly prepared by decomposing plant, food waste, recycling organic materials and manure. The resulting m ...
as a
soil conditioner,
anaerobic digestion
Anaerobic digestion is a sequence of processes by which microorganisms break down biodegradable material in the absence of oxygen. The process is used for industrial or domestic purposes to Waste management, manage waste or to produce fuels. Mu ...
for the production of
biogas
Biogas is a mixture of gases, primarily consisting of methane, carbon dioxide and hydrogen sulphide, produced from raw materials such as agricultural waste, manure, municipal waste, plant material, sewage, green waste and food waste. It is a ...
, forms of dry-combustion fuel such as pellets or
biochar
Biochar is the lightweight black residue, made of carbon and
ashes, remaining after the pyrolysis of biomass. Biochar is defined by the International Biochar Initiative as "the solid material obtained from the thermochemical conversion of ...
,
charcoal,
biodiesel
Biodiesel is a form of diesel fuel derived from plants or animals and consisting of long-chain fatty acid esters. It is typically made by chemically reacting lipids such as animal fat ( tallow), soybean oil, or some other vegetable oil ...
,
sludge
Sludge is a semi-solid slurry that can be produced from a range of industrial processes, from water treatment, wastewater treatment or on-site sanitation systems. For example, it can be produced as a settled suspension obtained from conventional ...
and plants or protein production as
animal fodder
Fodder (), also called provender (), is any agricultural foodstuff used specifically to feed domesticated livestock, such as cattle, rabbits, sheep, horses, chickens and pigs. "Fodder" refers particularly to food given to the animals (includi ...
.
Definitions
Fecal sludge management refers to the storage, collection, transport, treatment, and safe end use or disposal of fecal sludge.
Collectively, the collection, transport, treatment and end use or
reuse of excreta
Reuse of human excreta is the safe, beneficial use of treated human excreta after applying suitable treatment steps and risk management approaches that are customized for the intended reuse application. Beneficial uses of the treated excreta may ...
constitute the "value chain" of fecal sludge management.
Fecal sludge
Fecal sludge is defined very broadly as what accumulates in
onsite sanitation
Sanitation refers to public health conditions related to clean drinking water and treatment and disposal of human excreta and sewage. Preventing human contact with feces is part of sanitation, as is hand washing with soap. Sanitation systems ...
technologies and specifically is not transported through a
sewer. It is composed of
human excreta
Human waste (or human excreta) refers to the waste products of the human digestive system, menses, and human metabolism including urine and faeces. As part of a sanitation system that is in place, human waste is collected, transported, treated a ...
, but also anything else that may go into an onsite containment technology, such as flushwater, cleansing materials and
menstrual hygiene
Feminine hygiene products are personal care products used during menstruation, vaginal discharge, and other bodily functions related to the vulva and vagina. Products that are used during menstruation may also be called menstrual hygiene product ...
products,
grey water
Greywater (or grey water, sullage, also spelled gray water in the United States) refers to domestic wastewater generated in households or office buildings from streams without fecal contamination, i.e., all streams except for the wastewater fro ...
(i.e. bathing or kitchen water, including fats, oils and grease), and
solid waste. Hence, fecal sludge is highly variable, with a very wide range of quantities (i.e. produced and accumulated volumes) and qualities (i.e. characteristics).
[ ]
Text was copied from this source, which is available under
Creative Commons Attribution 4.0 International License
Fecal sludge is stored onsite, and is periodically collected and transported to a fecal sludge treatment plant, followed by safe disposal or end use.
When safely managed, fecal sludge that is collected from pit latrines can also be called "pit latrine sludge", whereas fecal sludge collected from septic tanks can also be called "septic tank sludge" or "septage".
Septage
Septage or "septic tank sludge" is fecal sludge that is accumulated and stored in a
septic tank
A septic tank is an underground chamber made of concrete, fiberglass, or plastic through which domestic wastewater ( sewage) flows for basic sewage treatment. Settling and anaerobic digestion processes reduce solids and organics, but the treatm ...
. Septage tends to be more dilute, as septic tanks are typically used with flush toilets (
blackwater) and can also include
grey water
Greywater (or grey water, sullage, also spelled gray water in the United States) refers to domestic wastewater generated in households or office buildings from streams without fecal contamination, i.e., all streams except for the wastewater fro ...
. Septic tanks also tend to have less solid waste, as they only receive things that can be flushed down a toilet (e.g.
toilet paper
Toilet paper (sometimes called toilet tissue or bathroom tissue) is a tissue paper product primarily used to clean the anus and surrounding anal region of feces after defecation, and to clean the perineal area and external genitalia of ur ...
). When operating as designed, a sludge blanket layer accumulates on the bottom of the tank, a scum layer that contains fats, oil and grease accumulates at the top, and the effluent or supernatant contains less solids.
Septage is periodically removed (with a frequency depending on tank capacity, system efficiency, and usage level, but typically less often than annually) from the septic tanks by specialized vehicles known as
vacuum trucks. They pump the septage out of the tank, and transport it to a local fecal sludge treatment plant. It can also be used by farmers for fertilizer, or stored in large septage waste storage facilities for later treatment or use on crops.
The term "septage" has been used in the United States since at least 1992. It has also been used in projects by the
United States Agency for International Development
The United States Agency for International Development (USAID) is an independent agency of the U.S. federal government that is primarily responsible for administering civilian foreign aid and development assistance. With a budget of over $27 b ...
in Asia. Another definition of septage is: "A historical term to define sludge removed from septic tanks."
[Tilley, E., Ulrich, L., Lüthi, C., Reymond, Ph. and Zurbrügg, C. (2014)]
Compendium of Sanitation Systems and Technologies (2nd Revised Edition)
Swiss Federal Institute of Aquatic Science and Technology (Eawag), Duebendorf, Switzerland
In India some government policy documents are using the term FSSM for "Fecal sludge and septage management".
Purposes and benefits
The overall goal of FSM is the protection of public and environmental health. FSM forms a key component of city-wide inclusive sanitation (CWIS), which considers all types of sanitation technologies in order to provide equitable, safe, and
sustainable sanitation for everyone.
CWIS employs a service delivery approach along the entire service chain, rather than just infrastructure provision.
Adequately and safely managed fecal sludge has the following benefits:
* Reduce the potential for human contact with fecal-borne pathogens by improving the functioning of onsite sanitation systems;
* Minimize odors and nuisances, and the uncontrolled discharge of organic matter from overflowing tanks or pits;
* Reduce indiscriminate disposal of collected fecal sludge;
* Production and sale of the end-products of the sludge treatment process. These products may include recycled water for agriculture and industry, soil conditioners from composting or co-composting materials, and energy products such as biogas, biodiesel, charcoal pellets, industrial powdered fuel, or electricity.
* Stimulate economic development, and job creation and livelihood opportunities, while addressing the issues of the social stigma and operator health and safety that continue to impact informal workers. This can also include jobs for contractors and equipment installers; for
sanitation workers
A sanitation worker (or sanitary worker) is a person responsible for cleaning, maintaining, operating, or emptying the equipment or technology at any step of the sanitation chain.World Bank, ILO, WaterAid, and WHO (2019)Health, Safety and Dignity ...
such as sludge collection personnel including drivers and emptiers; and for treatment and reuse systems operators.
Developments in the sector
Since the wider recognition of the importance of sanitation, marked by the UN declaring 2008 as the ‘Year of Sanitation’, there has been a steady increase in commitment, uptake, implementation, and knowledge generation in non-sewered sanitation.
The incorporation of the entire sanitation management service chain in the
Sustainable Development Goal (SDG) 6, as opposed to just providing access to toilets, has further established acknowledge of the importance of FSM. The SDGs were launched in 2015, and SDG 6 is for "clean water and sanitation for all by 2030"), launched in 2015, has further established acknowledgement of its importance.
There has also been an increase in the incorporation of fecal sludge management in national regulations and development agency agendas, increased funding from foundations and governments, and implementation of infrastructure and service provision.
There has been a rapid increase in evidence-based research and journal publications on the topic (e.g. for Africa and Asia
[Oxfam (2016)]
Septage Management Leader’s Guidebook - Philippines Edition
Oxfam, UK). There are rapidly evolving technology developments along the entire service chain. Some have the potential to alter the existing service chain, such as container-based sanitation, decentralized options, and innovations developed through the
Bill & Melinda Gates Foundation ‘Reinvent the Toilet Challenge’ since at least 2012.
Curriculums have been, and are continuing to be, developed and implemented. Initiatives include the Global Sanitation Graduate School, and freely available online courses, such as the Sandec MOOC series.
Challenges
In many
LMICs
A developing country is a sovereign state with a lesser developed industrial base and a lower Human Development Index (HDI) relative to other countries. However, this definition is not universally agreed upon. There is also no clear agreeme ...
, fecal sludge is still not properly managed. This may be due to a lack of mandated institutions and low awareness of the impact of poor sanitation; a lack of technical expertise and experience; an inability to source funds for to purchase of vacuum trucks and treatment, as well as a lack of knowledge necessary to initiate and implement successful FSM programs. This can result in the poor performance of onsite sanitation facilities (OSSFs), fecal sludge overflowing from containments, and the unsafe emptying and dumping of untreated fecal sludge into the environment.
Fecal sludge contains
pathogen
In biology, a pathogen ( el, πάθος, "suffering", "passion" and , "producer of") in the oldest and broadest sense, is any organism or agent that can produce disease. A pathogen may also be referred to as an infectious agent, or simply a germ ...
s, can generate odors and cause surface
water pollution
Water pollution (or aquatic pollution) is the contamination of water bodies, usually as a result of human activities, so that it negatively affects its uses. Water bodies include lakes, rivers, oceans, aquifers, reservoirs and groundwater. ...
, as well as
groundwater pollution
Groundwater pollution (also called groundwater contamination) occurs when pollutants are released to the ground and make their way into groundwater. This type of water pollution can also occur naturally due to the presence of a minor and unwante ...
.
Components
Fecal sludge management (FSM) requires safe and hygienic
septic tank
A septic tank is an underground chamber made of concrete, fiberglass, or plastic through which domestic wastewater ( sewage) flows for basic sewage treatment. Settling and anaerobic digestion processes reduce solids and organics, but the treatm ...
and
pit latrine
A pit latrine, also known as pit toilet, is a type of toilet that collects human feces in a hole in the ground. Urine and feces enter the pit through a drop hole in the floor, which might be connected to a toilet seat or squatting pan for use ...
emptying services, along with the effective treatment of solids and liquids and the reuse of treated produce where possible.
It may include a range of options including on-site and offsite treatment, and the dispersal or capture and further processing of the products of the treatment process into such as
biogas
Biogas is a mixture of gases, primarily consisting of methane, carbon dioxide and hydrogen sulphide, produced from raw materials such as agricultural waste, manure, municipal waste, plant material, sewage, green waste and food waste. It is a ...
,
compost and energy.
By type of dwellings
Cities
![Desludging fleet Manila Water](https://upload.wikimedia.org/wikipedia/commons/a/a5/Desludging_fleet_Manila_Water.jpg)
FSM is a critical sanitation service in cities and towns in all countries where households use onsite sanitation systems.
[Peal, A., Evans, B., Blackett, I., Hawkins, P., Heymans, C. (2015)]
A Review of Fecal Sludge Management in 12 Cities
- (Final Draft). World Bank - Water and Sanitation Program Citywide FSM programs may utilize multiple or one treatment facility, use stationary and mobile transfer stations, and engage with micro, small and medium-sized enterprises that may conduct some or all of the services.
Programs may be phased in over time to accommodate growing demand.
Peri urban areas
Peri urban areas are often less densely populated than urban centers. Therefore, they have more space and on-site sanitation systems can be effective for solid and liquid treatment. In most such peri-urban areas, it is less likely that they will be connected to a conventional centralized
sewerage system in the short or medium term. Therefore, these areas will rely on a mix of onsite-sanitation systems and services, decentralized wastewater management systems, or by condominial or
simplified sewerage
Simplified sewerage, also called small-bore sewerage, is a sewer system that collects all household wastewater ( blackwater and greywater) in small-diameter pipes laid at fairly flat gradients. Simplified sewers are laid in the front yard or unde ...
connected to decentralized or centralized treatment. In all of these situations, FSM is a necessary service to keep the sanitation systems functioning properly.
Rural areas
![Passing the faecal sludge to the top of the pit latrine](https://upload.wikimedia.org/wikipedia/commons/5/5d/Passing_the_faecal_sludge_to_the_top_of_the_pit_latrine.jpg)
Rural areas with low population density may not need formal FSM services if the local practice is to cover and rebuild latrines when they fill up. However, if this is not possible, rural areas often lack treatment facilities within a reasonable (say 30 minutes drive) distance; are difficult for tankers to access and often have limited demand for emptying making transport and treatment uneconomic, and unaffordable for most people. Therefore, options such as relocating latrines on-site, double (alternating) pit or
Arborloo
An arborloo is a simple type of composting toilet in which feces are collected in a shallow pit and a fruit tree is later planted in the fertile soil of the full pit. Arborloos have: a pit like a pit latrine but less deep; a concrete, ferroceme ...
toilets could be considered. Also sharing decentralized FSM services and sludge treatment between nearby villages, or direct safe removal burial of waste could be considered and organized.
Alternatives to fecal sludge producing systems
Most types of
dry toilets
A dry toilet (or non-flush toilet, no flush toilet or toilet without a flush) is a toilet which, unlike a flush toilet, does not use flush water. Dry toilets do not use water to move excreta along or block odors. They do not produce sewage, and a ...
(except for
pit latrines
A pit latrine, also known as pit toilet, is a type of toilet that collects human feces in a hole in the ground. Urine and feces enter the pit through a drop hole in the floor, which might be connected to a toilet seat or squatting pan for user ...
) do not generate fecal sludge but generate instead dried
feces (in the case of
urine-diverting dry toilet
A urine-diverting dry toilet (UDDT) is a type of dry toilet with urine diversion that can be used to provide safe, affordable sanitation in a variety of contexts worldwide. The separate collection of feces and urine without any flush water has ma ...
s) or
compost (in the case of
composting toilet
A composting toilet is a type of dry toilet that treats human waste by a biological process called composting. This process leads to the decomposition of organic matter and turns human waste into compost-like material. Composting is carried ou ...
s). For example, in the case of
Arborloo
An arborloo is a simple type of composting toilet in which feces are collected in a shallow pit and a fruit tree is later planted in the fertile soil of the full pit. Arborloos have: a pit like a pit latrine but less deep; a concrete, ferroceme ...
toilets, nothing is ever extracted from the pit and, instead, the lightweight
outhouse
An outhouse is a small structure, separate from a main building, which covers a toilet. This is typically either a pit latrine or a bucket toilet, but other forms of dry (non-flushing) toilets may be encountered. The term may also be used ...
superstructure is moved to another shallow hole and a tree is planted on top of the filled hole.
Management aspects
Selecting the operator of FSM services
FSM services are usually provided by formal and informal private sector service providers, local governments, water authorities and
utilities
A public utility company (usually just utility) is an organization that maintains the infrastructure for a public service (often also providing a service using that infrastructure). Public utilities are subject to forms of public control and ...
. Water utilities with a high percentage of water connectivity (homes with piped water connections) are logical operators of FSM programs. If water is sold to customers through a tariff, an additional tariff to cover FSM services may be added. For larger cities, it is usually the water and sewerage service provider that will be the most appropriate operator.
Local governments may choose to provide services by using their own staff and resources for collection, transportation and treatment. This is often the case in smaller cities or municipalities where the water utility may not have a broad reach. In many cases, cooperation between the city government and the water utility may be strategically advantageous. Dumaguete City, Philippines is one example where the Water District (utility) and Local Government have joint ownership and responsibilities for the FSM program. Organized larger scale FSM programs may be able to provide the service more cheaply and more hygienically than the independent private operators working on an ''ad hoc'' basis. Ensuring services are affordable is an important selling point when promoting the program to citizens and encouraging them to participate.
The local private sector is an important player in providing FSM services. In such cases, private sector contractors may work directly for households (under regulation) or bid on desludging contracts let by the city. The private sector can also provide services in operating and maintaining the treatment works, and in processing and selling the commodities resulting from the treatment process. San Fernando City, La Union, Philippines is an example of a local government that has contracted out the treatment facility construction and collection program to the private sector.
Scheduled desludging programs
Scheduled desludging is a planned effort by the local government or utility to ensure regular desludging of septic tanks. In this process, every property is covered along a defined route and the property occupiers are informed in advance about desludging that will take place.
The actual desludging (or emptying of septic tanks) can be done through a public private partnership (PPP) arrangement.
In Southeast Asia, there is (in 2016) increasing interest in scheduled desludging programs as a means of providing services. A WSP study recommended that efforts to introduce scheduled emptying should focus first on areas where demand was greatest, moving on to other areas when the success of scheduled emptying had been demonstrated in these areas.
Analysis of pit and tank desludging records for Palu in Indonesia revealed that existing demand for desludging services varied between sub-districts, with demand being greatest in well-established areas and least in urban fringe areas.
There are multiple benefits of scheduled desludging services in the Indian context: Achieves the norms through regular desludging, reduces high prices of desludging, removes the need for manual labor, improves environmental and public health impacts, links with local taxes rather than with user charges.
Scheduled desludging has been initiated in several Asian counties including the Philippines, Malaysia, Vietnam, Indonesia, and India.
A program by
SNV (Netherlands Development Organisation) has developed scheduled emptying services in Indonesia, Nepal and Bangladesh as part of a broader urban sanitation program during 2014-2017.
Elements of successful programs
![Desludging truck in action Nepal](https://upload.wikimedia.org/wikipedia/commons/b/b8/Desludging_truck_in_action_Nepal.jpg)
FSM services can be provided as demand based (often called on-request, on-call, on-demand, ad-hoc or non-scheduled) or scheduled (also known as regular) desludging, or a combination of both. Under either mechanism, OSSFs are desludged on a periodic basis or when the household requests it or due to inspection by a competent authority indicates desludging is needed.
An analysis of 20 FSM Innovation Case Studies and research and advocacy of successful programs carried out by
Oxfam
Oxfam is a British-founded confederation of 21 independent charitable organizations focusing on the alleviation of global poverty, founded in 1942 and led by Oxfam International.
History
Founded at 17 Broad Street, Oxford, as the Oxford Co ...
Philippines has demonstrated that common elements for successful FSM programs include:
* Well formulated and practical policy, rules and regulation: While these are essential they are almost useless, even counterproductive, on their own, and must be supported by complementary factors such as those below;
* Local leadership and clearly mandated and resourced institutions to manage services, even where actual services are delivered by the private sector;
* Partnerships between stakeholders contributes to developing services at scale, building community confidence and achieving sustainability;
* A sustained program of community engagement, marketing and awareness raising is as essential to FSM as sludge treatment – but is frequently under-valued, under-budgeted and sometimes abandoned after an initial period;
* Capacity-building for FSM service providers helps ensure that they can effectively meet all segments of demand and achieve long-term viability. This may include training in both technical matters and business management, and the facilitation of capital formation through grants, equipment leasing, loan guarantees and other financial instruments;
* Tariffs that are pro-poor and representative of operational costs for providing the service;
* Technology that is appropriate to the capacity to operate and maintain the system and the realities of the value chain.
Sanitation workers
Sanitation workers
A sanitation worker (or sanitary worker) is a person responsible for cleaning, maintaining, operating, or emptying the equipment or technology at any step of the sanitation chain.World Bank, ILO, WaterAid, and WHO (2019)Health, Safety and Dignity ...
are the people responsible for cleaning, maintaining, operating, or emptying a
sanitation
Sanitation refers to public health conditions related to clean drinking water and treatment and disposal of human excreta and sewage. Preventing human contact with feces is part of sanitation, as is hand washing with soap. Sanitation syste ...
technology at any step of the
sanitation
Sanitation refers to public health conditions related to clean drinking water and treatment and disposal of human excreta and sewage. Preventing human contact with feces is part of sanitation, as is hand washing with soap. Sanitation syste ...
chain.
[World Bank, ILO, WaterAid, and WHO (2019)]
Health, Safety and Dignity of Sanitation Workers: An Initial Assessment
World Bank, Washington, DC. These workers contribute to safe fecal sludge management.
Transport options
Collection vehicles and equipment
![Fig](https://upload.wikimedia.org/wikipedia/commons/1/1b/Fig.1._Gulper_used_to_desludge_tanks_in_eThekwini%2C_South_Africa.JPG)
If the fecal sludge is liquid enough, it is usually collected by using vacuum pumps or centrifugal style booster pumps. A variety of manual and motorized devices designed to excavate thick and viscous sludge and accumulated trash are also available in the market.
After sitting for years in septic tanks and pit latrines, the accumulated sludge becomes hardened and is very difficult to remove. It is still common that workers enter pits in order to desludge them, even though this practice is generally unsafe and undesirable (in India, this practice is called "
manual scavenging
Manual scavenging is a term used mainly in India for "manually cleaning, carrying, disposing of, or otherwise handling, human excreta in an insanitary latrine or in an open drain or sewer or in a septic tank or a pit". Manual scavengers usually ...
"). A number of low-cost pumping systems exist to remove this hardened sludge hygienically from the ground surface, although many of them are still in the experimental stage (e.g. Excravator, Gulper, e-Vac).
Fecal sludge can also be treated inside the tank or pit as well, by use of the "in-pit lime stabilization process", which treats the waste before it is removed from the tank or pit. This methodology was first pioneered by iDE Cambodia in 2010. Once removed, it is transported to onsite or off site treatment and processing facilities.
Some advanced transfer stations and vacuum trucks can dewater fecal sludge to some extent, and this water may be placed in sewer lines to be treated in wastewater treatment plants.
This allows more sludge to be dealt with more efficiently and may constitute one of the best cases of co-treatment of fecal sludge in wastewater treatment plants.
Transfer stations
Transfer stations are intermediary drop off locations often used where treatment facilities are located too far away from population centers to make direct disposal feasible. In other locations, traffic concerns or local truck bans during daylight hours may make transfer stations feasible. In addition, municipalities where a significant percentage of homes cannot be accessed by tanker truck should utilize transfer stations. Transfer stations are used if:
* More than 5% of the homes are inaccessible by a vacuum truck;
* The treatment plant is too far away from the homes for transport in one haul to be practical;
* Trucks are not permitted on the streets during the day; or
* Heavy traffic during daylight hours impedes the movement of vacuum trucks.
Mobile transfer stations
Mobile transfer stations are nothing more than larger tanker trucks or trailers that are deployed along with small vacuum trucks and motorcycle or hand carts. The smaller vehicles discharge to the larger tanker, which then carries the collected sludge to the treatment plant. These work well in scheduled desludging business models.
Fixed transfer stations
Fixed transfer stations are dedicated facilities installed strategically throughout the municipality that serve as drop off locations for collected fecal sludge. They may include a receiving station with screens, a tank for holding the collected waste, trash storage containers, and wash down facilities. These may be more appropriate for FSM programs using the "call-for-service" business model.
While static transfer stations are fixed tanks, mobile transfer stations are simply tanker trucks or trailers that work alongside the SVVs and actually do the longer haul transferring of the waste from the community to the treatment plant. Mobile transfer stations work best for scheduled desludging programs where there are no traffic restrictions or truck bans, and a relatively large number of homes that are inaccessible to the larger vehicles.
Treatment processes
Characteristics of fecal sludge
Characteristics of fecal sludge may vary widely due to climate, toilet type, diet and other variables. Fecal sludge can be grouped by consistency as "liquid" (total solids or TS <5%), "slurry" (TS 5-15%), "semi-solid" (TS 15-25%), and "solid" (TS >25%).
Quantities and qualities of fecal sludge and wastewater are very different, with the range of fecal sludge characteristics being 1-2 orders of magnitude higher than wastewater.
The result of the demographic, environmental, and technical factors that influence characteristics of fecal sludge is a high level of heterogeneity that complicates characterization.
In the absence of actual data, designers often use default values, such as 2,000 mg/L for BOD and 5,000 mg/L of TSS in order to size the treatment system. However, this often results in over-design or under-design of fecal sludge treatment plants. This is because there is often no "standard range of variation" for particular properties, and findings from one study cannot necessarily be used as a base of comparison to another.
Research has shown that correlations to spatially available data can help predict quantities and qualities of fecal sludge. The relevant indicators for the prediction include income level, users, volume, emptying frequency, and truck size. Using these correlations in characteristics could provide a way to reduce analytical costs for fecal sludge analysis.
Performing a waste characterization study helps to understand local conditions and provides data that factors into treatment plant sizing. It can also help to estimate the value of the products that can be derived from the treatment process.
The main physico-chemical parameters commonly measured to characterize fecal sludge include:
BOD,
total suspended solids
Total suspended solids (TSS) is the dry-weight of suspended particles, that are not dissolved, in a sample of water that can be trapped by a filter that is analyzed using a filtration apparatus known as sintered glass crucible. TSS is a water qu ...
, % solids, indication of sand,
COD
Cod is the common name for the demersal fish genus '' Gadus'', belonging to the family Gadidae. Cod is also used as part of the common name for a number of other fish species, and one species that belongs to genus ''Gadus'' is commonly not call ...
,
ammonium, total nitrogen and total phosphorus, Fats, Oil and Grease (FOG),
Sludge Volume Index (SVI), pH,
alkalinity
Alkalinity (from ar, القلوي, al-qaly, lit=ashes of the saltwort) is the capacity of water to resist acidification. It should not be confused with basicity, which is an absolute measurement on the pH scale.
Alkalinity is the strength ...
.
Relatively little data exists on
pathogen
In biology, a pathogen ( el, πάθος, "suffering", "passion" and , "producer of") in the oldest and broadest sense, is any organism or agent that can produce disease. A pathogen may also be referred to as an infectious agent, or simply a germ ...
content in fecal sludge. One study from rural Bangladesh determined 41
helminth eggs per g of fecal sludge from pit latrines.
The characteristics of fecal sludge may be influenced by:
* Methods, techniques and the skill levels of personnel conducting the desludging;
* The efficiency of the different types of equipment used in desludging;
* Seasonality - presence of groundwater or flood water that may infiltrate into tanks and dilute the contents;
* The last time the tank was desludged (age of fecal sludge).
Conventional treatment processes
Fecal Sludge is often processed through a series of treatment steps to first separate the liquids from the solids, and then treat both the liquid and solid trains while recovering as much of the energy or nutritive value as possible.
Common processes at fecal sludge treatment plants include:
* Fecal sludge reception - where the truck interfaces with the treatment plant and sludge is unloaded.
* Preliminary treatment - to remove garbage, sand, grit, and FOG (fats, oil and grease)
* Primary treatment - simple separation of liquid and solids by physical means (dewatering and thickening), e.g. with drying beds
* Liquids treatment - for example by using
constructed wetlands
A constructed wetland is an artificial wetland to treat sewage, greywater, stormwater runoff or industrial wastewater. It may also be designed for land reclamation after mining, or as a mitigation step for natural areas lost to land developmen ...
,
waste stabilization ponds,
anaerobic digesters
Anaerobic digestion is a sequence of processes by which microorganisms break down biodegradable material in the absence of oxygen. The process is used for industrial or domestic purposes to manage waste or to produce fuels. Much of the ferm ...
* Solids processing - using the solids resulting from fecal sludge treatment for beneficial use where possible.
Constructed wetlands are gaining attention as a low-cost treatment technology that can be constructed in many instances using local materials and labor. For sites with enough land and a ready supply of gravel and sand, this technology offers low cost, scalability, and simple operation.
Drying beds
Simple sludge drying beds can be used for dewatering and drying, as they are a cheap and simple method to dry fecal sludge (they are also widely used to dry
sewage sludge
Sewage sludge is the residual, semi-solid material that is produced as a by-product during sewage treatment of industrial or municipal wastewater. The term " septage" also refers to sludge from simple wastewater treatment but is connected to s ...
). Drainage water must be captured; drying beds are sometimes covered but usually left uncovered.
Drying beds are typically composed of four layers (from top to bottom):
* Sludge;
* 10-15 cm of sand (sometimes with wires or plastic mesh on top of it, to prevent it being removed when the dried sludge is extracted);
* 10 cm of fine gravel;
* 15-20 cm of coarse gravel and drainage pipes.
Fecal sludges behave differently during dewatering processes than
wastewater sludges.
The amount of
extracellular polymeric substances (EPS) can be an important predictor for faecal sludge dewatering performance.
Fecal sludge from
public toilet
A public toilet, restroom, public bathroom or washroom is a room or small building with toilets (or urinals) and sinks for use by the general public. The facilities are available to customers, travelers, employees of a business, school pupils ...
s took longer to dewater than sludge from other sources, and had turbid supernatant after settling.
Grass
Poaceae () or Gramineae () is a large and nearly ubiquitous family of monocotyledonous flowering plants commonly known as grasses. It includes the cereal grasses, bamboos and the grasses of natural grassland and species cultivated in lawns an ...
es with
adventitious roots Important structures in plant development are buds, shoots, roots, leaves, and flowers; plants produce these tissues and structures throughout their life from meristems located at the tips of organs, or between mature tissues. Thus, a living pla ...
may also be planted in drying beds, allowing for reduction of odor, collection over longer periods, production of
forage
Forage is a plant material (mainly plant leaves and stems) eaten by grazing livestock. Historically, the term ''forage'' has meant only plants eaten by the animals directly as pasture, crop residue, or immature cereal crops, but it is also used ...
, and more decomposition of the final
biosolids
Biosolids are solid organic matter recovered from a sewage treatment process and used as fertilizer. In the past, it was common for farmers to use animal manure to improve their soil fertility. In the 1920s, the farming community began also to use ...
by the time they are extracted. The roots introduce oxygen and maintain the
permeability of the sludge.
Earthworm
An earthworm is a terrestrial invertebrate that belongs to the phylum Annelida. They exhibit a tube-within-a-tube body plan; they are externally segmented with corresponding internal segmentation; and they usually have setae on all segments. T ...
s may also play an important role in such beds.
Emerging technologies
Emerging technologies for fecal sludge treatment include:
* Technologies that can produce a dried or carbonized solid fuel from fecal sludge include: drying,
pelletizing,
hydrothermal carbonization
Hydrothermal carbonization (HTC) (also referred to as "aqueous carbonization at elevated temperature and pressure") is a chemical process for the conversion of organic compounds to structured carbons. It can be used to make a wide variety of nanost ...
, and slow
pyrolysis
The pyrolysis (or devolatilization) process is the thermal decomposition of materials at elevated temperatures, often in an inert atmosphere. It involves a change of chemical composition. The word is coined from the Greek-derived elements ''py ...
.
*Thermal processes which can achieve cost effectiveness by eliminating the need for separate processes. They convert the fecal sludge along with certain fractions of
sewage sludge
Sewage sludge is the residual, semi-solid material that is produced as a by-product during sewage treatment of industrial or municipal wastewater. The term " septage" also refers to sludge from simple wastewater treatment but is connected to s ...
or municipal solid waste to produce energy or fuel by using certain
sewage sludge treatment
Sewage sludge treatment describes the processes used to manage and dispose of sewage sludge produced during sewage treatment. Sludge treatment is focused on reducing sludge weight and volume to reduce transportation and disposal costs, and on red ...
technologies.
* Biodiesel can be manufactured by using fats, oils and grease as feedstocks. Research by
RTI International
Research Triangle Institute, trading as RTI International, is a nonprofit organization headquartered in the Research Triangle Park in North Carolina. RTI provides research and technical services. It was founded in 1958 with $500,000 in funding fr ...
is being conducted to use fecal sludge for biodiesel production.
* Electricity can be produced by thermal processes that burn fecal and solid waste together to maintain stable combustion and the heat is used to make steam that drives generators.
Solar thermal dryers
Solar thermal dryers rely on the collection of the solar thermal energy for drying and pasteurization of fecal sludge. In these systems, the sludge is placed inside an enclosure of transparent or opaque walls, with a ventilation system for moisture evacuation. The sludge can be dried by hot air that was heated by a solar thermal collector (indirect solar dryer), by direct exposure to solar radiation (direct solar dryer), or by both modes (mixed solar dryer).
Co-treatment at wastewater treatment plants
Co-treatment of septage at
wastewater treatment plants
Wastewater treatment is a process used to remove contaminants from wastewater and convert it into an effluent that can be returned to the water cycle. Once returned to the water cycle, the effluent creates an acceptable impact on the environmen ...
may be considered where the volume of septage removed from on-site facilities is small, as will be the case in situations where most households have access to
sewerage. However, the high strength of septage and fecal sludge means that relatively small volumes of both can have a large impact on the organic, suspended solids, and nitrogen loads on a wastewater treatment plant. Possible consequences include an increase in the volume of screenings and grit requiring removal; increased odour emission at headworks; increased scum and sludge accumulation rates; and increased organic loading, leading to overloading and process failure, and the potential for increased odour and foaming in aeration tanks. Because of their partly digested nature, septage and fecal sludge will usually degrade at a slower rate than municipal wastewater. Therefore, their presence is likely to have an adverse impact on the efficacy of treatment processes. The intermittent nature of fecal sludge and septage loading can also amplify the problems identified above.
Despite these possible drawbacks, wastewater treatment facilities with spare capacity are a potential resource to be investigated. Even where co-treatment is not an option, existing wastewater treatment plants may provide land in strategic locations, close to areas of demand for septage management services. Separate preliminary treatment and solids-liquid separation facilities should always be provided for septage/fecal sludge. Solids-liquid separation will reduce both the overall load and the proportion of digested material in the liquid fraction and will thus lessen the possibility that it will disrupt wastewater treatment processes. Separated solids can be treated along with the sludge produced in sedimentation tanks during the wastewater treatment process.
Technology selection
![Training of enumerators for septage survey Nepal](https://upload.wikimedia.org/wikipedia/commons/0/05/Training_of_enumerators_for_septage_survey_Nepal.jpg)
A formal process should be used for making an informed technology selection for the treatment of the fecal sludge.
It is usually ''a'' collaborative process conducted by stakeholders, consultants, the operator and the future owner of the facility''.'' The process is based on a long term vision planning with stakeholders as part of citywide sanitation planning. The expected waste flows (volume), their strength, characteristics, and variability in each area need to be known. A formal and transparent process for developing appropriate plans and designs for wastewater and fecal sludge treatment plants will achieve local buy-in and ownership of technology decisions, which is critical for the long term success and sustainability of the program.
Reuse options
![Sludge pellets after LaDePa process (8151957937)](https://upload.wikimedia.org/wikipedia/commons/8/88/Sludge_pellets_after_LaDePa_process_%288151957937%29.jpg)
Resource recovery from fecal sludge can take many forms, including as a fuel, soil amendment, building material, protein, animal fodder, and water for irrigation.
Some of the by-products from fecal sludge treatment processes have the potential to offset some of the costs of collection and treatment, thereby reducing tariffs for the households. However, value addition all the way to biogas, biodiesel and electricity is difficult to achieve in practice due to technological and operational challenges.
Composting
Composting is a process whereby organic matter is digested in the presence of oxygen with the byproduct of heat. For fecal sludge, the heat deactivates the pathogens while the digestion process breaks down the organic matter into a humus-like material that acts as a soils amendment, and nutrients that are broken down into a form that is more easily taken up by plants. Properly treated fecal sludge can be reused in agriculture.
Fecal sludge is rich in nitrogen. When fecal sludge is mixed with materials that are rich in carbon, such as shredded crop wastes, the composting process can be maximized. Proper mixture to achieve a ratio of 20 to 1 to 30 to 1 of carbon to nitrogen is best.
Solid fuel
Resource recovery as a solid fuel has been found to have high market potential in
Sub-Saharan Africa
Sub-Saharan Africa is, geographically, the area and regions of the continent of Africa that lies south of the Sahara. These include West Africa, East Africa, Central Africa, and Southern Africa. Geopolitically, in addition to the List of sov ...
.
The selection of the fuel type will depend on: (1) the intended use of the fuel (e.g. combustion technology, user/handling requirements, and amount required); and (2) the properties of the input fecal sludge (e.g. level of stabilization, sand content, and moisture content). Once suitable technology options are identified, they must subsequently be evaluated for best fit in the local context (e.g. local capacity for electricity, land, and technical (operation and maintenance) requirements).
Others
Biogas
Biogas is a mixture of gases, primarily consisting of methane, carbon dioxide and hydrogen sulphide, produced from raw materials such as agricultural waste, manure, municipal waste, plant material, sewage, green waste and food waste. It is a ...
is a renewable energy that is a byproduct of the
anaerobic digestion
Anaerobic digestion is a sequence of processes by which microorganisms break down biodegradable material in the absence of oxygen. The process is used for industrial or domestic purposes to Waste management, manage waste or to produce fuels. Mu ...
process.
Treated effluent can be used for agricultural or landscape
irrigation
Irrigation (also referred to as watering) is the practice of applying controlled amounts of water to land to help grow Crop, crops, Landscape plant, landscape plants, and Lawn, lawns. Irrigation has been a key aspect of agriculture for over 5,00 ...
.
Costs and fees
FSM is considered an entry point for
sanitation
Sanitation refers to public health conditions related to clean drinking water and treatment and disposal of human excreta and sewage. Preventing human contact with feces is part of sanitation, as is hand washing with soap. Sanitation syste ...
improvement programs that are led by local governments. Such programs may include tariffs or user fees, promotions campaigns to raise the willingness to pay for the service, and local ordinances that define the rules and regulations governing FSM. In the Philippines, tariffs around US$1 per family per month are generally enough to achieve full cost recovery within a period of 3 to 7 years.
Promotional campaigns are used to raise the willingness to pay for services, and local procedures and ordinances provide additional incentives for compliance.
Synergies with other sectors
FSM is but one aspect of citywide sanitation that also includes:
*
Municipal solid waste
Municipal solid waste (MSW), commonly known as trash or garbage in the United States and rubbish in Britain, is a waste type consisting of everyday items that are discarded by the public. "Garbage" can also refer specifically to food waste ...
management;
* Drainage and
greywater
Greywater (or grey water, sullage, also spelled gray water in the United States) refers to domestic wastewater generated in households or office buildings from streams without fecal contamination, i.e., all streams except for the wastewater from ...
management;
* Wastewater collection and treatment including effluent overflows from on-site systems where soils based dispersal systems are insufficient to assimilate the volume;
* Water safety; and
* Food safety.
There are important synergies between many of these services and FSM, and investigating co-management opportunities can yield benefits. MSW can often be co-managed with fecal waste, especially when thermal treatment technologies are used.
Food waste
Food loss and waste is food that is not eaten. The causes of food waste or loss are numerous and occur throughout the food system, during production, processing, distribution, retail and food service sales, and consumption. Overall, about o ...
from restaurants and markets can be co-composted with fecal waste to produce a high value soils amendment. Fats, Oil and Grease (FOG) from commercial grease traps can be added to biodigesters to increase methane production, or used in conjunction with fecal sludge as a feedstock for biodiesel production.
Water supply
Water supply is the provision of water by public utilities, commercial organisations, community endeavors or by individuals, usually via a system of pumps and pipes. Public water supply systems are crucial to properly functioning societies. Thes ...
is also closely linked with FSM as it is often the water utility that will manage programs and their customers that will pay for services through tariffs.
Examples
Dumaguete, the Philippines
USAID has supported efforts to introduce scheduled desludging services in some countries in Southeast Asia. The first of these was in Dumaguete in the Philippines.
The program was run jointly by the city government and the Dumaguete City Water District, with the former operating the treatment plant and the Water District conducting the desludging.
[Blackett, I. and Hawkins, P. (2017)]
FSM Innovation Case Studies - Case Studies on the Business, Policy and Technology of Faecal Sludge Management
(second edition). Bill & Melinda Gates Foundation, Seattle, USA, The cost of the scheme was covered by adding a tariff of 2 pesos (about 5 US cents) to the water bill for each cubic meter of water consumed (about one US dollar per family per month). This approach was possible because around 95% of residents had a connection to the Water District reticulation system. Trucks were to move from neighborhood to neighborhood on a scheduled cycle, emptying pits on a regular 3-4 year cycle. This approach requires a database of all pits and septic tanks requiring desludging. However, Dumaguete has by 2018 reverted to an ‘on-call’ system, the cost of which is still covered by the surcharge on the
water tariff A water tariff (often called ''water rate'' in the United States and Canada) is a price assigned to water supplied by a public utility through a piped network to its customers. The term is also often applied to wastewater tariffs. Water and wastewat ...
. It seems that users prefer this small regular payment to having to make large payments when tanks require desludging.
See also
*
Biosolids
Biosolids are solid organic matter recovered from a sewage treatment process and used as fertilizer. In the past, it was common for farmers to use animal manure to improve their soil fertility. In the 1920s, the farming community began also to use ...
- treated sewage sludge
*
Ecological Sanitation
*
Nightsoil
Night soil is a historically used euphemism for human excreta collected from cesspools, privies, pail closets, pit latrines, privy middens, septic tanks, etc. This material was removed from the immediate area, usually at night, by workers emplo ...
- a historical term for a material similar to fecal sludge
*
Sewage sludge treatment
Sewage sludge treatment describes the processes used to manage and dispose of sewage sludge produced during sewage treatment. Sludge treatment is focused on reducing sludge weight and volume to reduce transportation and disposal costs, and on red ...
*
WASH
WASH (or Watsan, WaSH) is an acronym that stands for "water, sanitation and hygiene". It is used widely by non-governmental organizations and aid agencies in developing countries. The purposes of providing access to WASH services include achievi ...
- water supply, sanitation, hygiene
References
External links
Sustainable Sanitation Alliance library (documents on FSM)Documents about fecal sludge managementin the library of the
Sustainable Sanitation Alliance
The Sustainable Sanitation Alliance (SuSanA) is a loose network of organizations who are "working along the same lines towards achieving sustainable sanitation". It began its work in 2007, one year before the United Nations International Year o ...
(SuSanA)
Faecal Sludge Management (FSM) book - Systems Approach for Implementation and Operationby EAWAG (2014), in English and several other languages
{{wastewater
Sanitation
Feces
Sewerage
Environmental engineering