<!{|style="float: left;"|{{Language-box|english_link=Solids- table at top of page with logo, picture, Application level, Management level, and input-output tables -->free_Sewer|french_link=Réseau_d’égout_simplifié_sans_matières_solides|spanish_link=Alcantarillados_Libres_de_Solidos|hindi_link=coming soon|malayalam_link=coming soon|tamil_link=coming soon | korean_link=coming soon | chinese_link=Coming soon | indonesian_link=Coming soon | japanese_link=Coming soon}}|}
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[[Image:Icon_solids_free_sewer.png |right|95px]]<br>'''A Solids-Free Sewer is a network of small diameter pipes that transports solids-free or pre-treated wastewater (such as [[Septic Tank]] or settling tank effluent) to a treatment facility for further treatment or to a discharge point. Solids-Free Sewers are also referred to as settled, small-bore, small-diameter, variable-grade gravity, or septic tank effluent gravity sewers.'''<br>
A precondition for Solids-Free Sewer networks is efficient pre-treatment at the household level. The interceptor, septic or settling tank removes settleable particles that could clog small pipes. A grease trap should also be added. Because there is little risk of clogging, the sewers do not have to be self-cleaning (i.e. no minimum flow velocity) and can therefore be laid at shallow depths, can have fewer inspection points (manholes), can follow the topography more closely and have inflective gradients (i.e. negative slope). When the sewer roughly follows the ground contours, the flow in the sewer is allowed to vary between open channel flow and pressure (full-bore) flow. However, care should be taken with negative slopes as they may lead to surging above the ground level during peak flows. Inspection points should be provided at major connection points or when the size of the pipe changes[[Image:Icon_solids_free_sewer.png |right|80px]]
Despite the possibility that some portions of the pipe can rise higher when going downstream, for the total pipe the downstream end of the '''A solids-free sewer must be lower than the upstream end. When choosing is a pipe network of small-diameter pipes that transports pre-treated and solids-free wastewater (such as Septic Tank effluent). It can be installed at least 75mm), the a shallow depth of water in the pipe during peak and does not require a minimum wastewater flow within each section must be less than the diameter of the pipe. In sections where there is pressure flow, the invert of any interceptor tank outlet must higher than the hydraulic head within the sewer just prior or slope to the point of connection otherwise the liquid will backflow into the tank. If this condition is not met, then either select the next larger pipe diameter for the sewer or increase the depth at which the sewer is laidfunction.'''
{{procontable | pro=- Greywater can be managed at the same time. <br> Solids- Can be built and repaired with locally available materialsfree sewers are also referred to as settled, smallbore, variable-grade gravity, or septic tank effluent gravity sewers. <br> A precondition for solids- Construction can provide short-term employment to local labourersfree sewers is efficient primary treatment at the household level. <br> An interceptor, typically a single- Capital costs are less than chamber [[Conventional Gravity Sewer|Conventional Gravity SewersSeptic Tank]]; low operating costs(S. <br> - Can be extended as a community changes and grows9), captures settleable particles that could clog small pipes. | con=- Requires expert design and construction supervisionThe solids interceptor also functions to attenuate peak discharges. <br> - Requires repairs Because there is little risk of depositions and removals of blockages more frequently than a Conventional Gravity Sewer. <br> clogging, solids- Requires education and acceptance free sewers do not have to be used correctlyself-cleansing, i.e., no minimum flow velocity or tractive tension is needed. <br> - Effluent and sludge They require few inspection points, can have inflective gradients (from interceptorsi.e., negative slopes) requires secondary treatment and/or appropriate dischargefollow the topography.<br>When the sewer roughly follows the ground contours, the flow is allowed to vary between open channel and pressure (full-High water consumption for excreta removalbore) flow. }}
==Adequacy=Design Considerations=== If the interceptors are correctly designed and operated, this type of sewer does not require self-cleansing velocities or minimum slopes. Even inflective gradients are possible, as long as the downstream end of the sewer is lower than theupstream end. In sections where there is pressure flow, the water level in any interceptor tank must be higher than the hydraulic head within the sewer, otherwise the liquid will flow back into the tank. At high points in sections with pressure flow, the pipes must be ventilated.
Solids-Free Sewers are appropriate free sewers do not have to be installed on a uniform gradient with a straight alignment between inspection points. The alignment may curve to avoid obstacles, allowing for both full and partially filled flowsgreater construction tolerance. Although a constant supply A minimum diameter of water 75 mm is required, less water is to facilitate cleaning. Expensive manholes are not needed compared to the Simple Sewer because self-cleansing velocities access for mechanical cleaning equipment is not necessary. Cleanouts or flushing points are sufficient and are not requiredinstalled at upstream ends, high points, intersections, or major changes in direction or pipe size. Compared to manholes, cleanouts can be more tightly sealed to prevent stormwater from entering.
[[Septic Tank|Septic Tanks]] Stormwater must be excluded as it could exceed pipe capacity and Solidslead to blockages due to grit depositions. Ideally, there should not be any storm-Free Sewers can and groundwater in the sewers, but, in practice, some imperfectly sealed pipe joints must be built for new areasexpected. Estimates of groundwater infiltration and stormwater inflow must, therefore, or a Solids-Free Sewer can be connected to an existing primary treatment technology where local infiltration is inappropriatemade when designing the system. A Solids-Free Sewer The use of PVC pipes can be built for 20% to 50% less than [[Conventional Gravity Sewer|Conventional Gravity Sewerage]]minimize the risk of leakages.
This technology must <br>{{procontable | pro=- Does not require a minimum gradient or flow velocity <br>- Can be connected to an appropriate [[(Semiused where water supply is limited <br>- Lower capital costs than conventional gravity sewers; low operating costs <br>- Can be extended as a community grows <br>-) Centralized Treatment SystemGreywater can be managed concurrently|(Semicon=-) Centralized Treatment technology]] that can receive the wastewater. It is appropriate Space for densely populated areas where there interceptors is no space for required <br>- Interceptors require regular desludging to prevent clogging <br>- Requires training and acceptance to be used correctly <br>- Requires repairs and removals of blockages more frequently than a [[Soak Pit]] or [[Leach Field]]. This type of conventional gravity sewer is best suited to urban <br>- Requires expert design and less appropriate in lowconstruction <br>-density or rural areas.Leakages pose a risk of wastewater exfiltration and groundwater infiltration and are difficult to identify}}
==Health Aspects/Acceptance=Appropriateness===This type of sewer is best suited to medium-density (peri-)urban areas and less appropriate in low-density or rural settings. It is most appropriate where there is no space for a [[Leach Field]] (D.8), or where effluents cannot otherwise be disposed of onsite (e.g., due to low infiltration capacity or high groundwater). It is also suitable where there is undulating terrain or rocky soil. A solids-free sewer can be connected to existing Septic Tanks where infiltration is no longer appropriate (e.g., due to increased housing density and/or water use).
This technology requires regular maintenance on the part of the users and is therefore, not as passive as As opposed to a [[Conventional Gravity Simplified Sewer|Conventional Gravity Sewers]](C. Users must assume some level of responsibility for the 4) a solids-free sewer can also be used where domestic water consumptionis limited. This technology and accept is a flexible option that some potentially unpleasant maintenance may can be required. Also, users should be aware that, because easily extended as the system is community based, they may have to work with and/or coordinate maintenance activities with other userspopulation grows. The system will provide a high level Because of service shallowexcavations and may offer the use of fewer materials, it can be built at considerably lower cost than a significant improvement to non-functioning [[Leach FieldConventional Gravity Sewer |Leach FieldsConventional Sewer]](C.6).
==Upgrading=Health Aspects/Acceptance=== If well constructed and maintained, sewers are a safe and hygienic means of transporting wastewater. Users must be well trained regarding the health risks associated with removing blockages and maintaining interceptor tanks.
Solids-Free Sewers ===Operation & Maintenance=== Trained and responsible users are good upgrading options for [[Leach Field|Leach Fields]] essential to avoid clogging by trash and other solids. Regular desludging of the Septic Tanks is critical to ensure optimal performance of the sewer. Periodic flushing of the pipes is recommended to insure against blockages. Special precautions should be taken to prevent illegal connections, since it is likely that have become clogged interceptors would not be installed and/solids would enter the system. The sewerage authority, a private contractor or saturated with time as well as users committee should be responsible for rapidly growing areas the management of the system, particularly, to ensure that would not accommodate more [[Septic Tank|Septic Tanks]] with Leach Fieldsthe interceptorsare regularly de-sludged and to prevent illegal connections.
==Maintenance=Upgrading===Solids-Free Sewers are good upgrading options for Leach Fields that have become clogged and/or saturated with time as well as for rapidly growing areas that would not accommodate more Septic Tanks with Leach Fields.
The septic===References===* Azevedo Netto, J. and Reid, R. (1992). [https:/interceptor tank must be regularly maintained /www.ircwash.org/sites/default/files/332-92IN-9897.pdf Innovative and desludged to insure optimal performance of the SolidsLow-Free Sewer networkCost Technologies Utilized in Sewerage]. If the pre-treatment is efficientTechnical Series No. 29, Environmental Health Program, Pan American Health Organization, the risk of clogging in the pipes is lowWashington, but some maintenance will be required periodicallyD.C. The sewers should be flushed once a year as part of the regular maintenance regardless of their performance, US.(A short summary and component diagrams – Chapter 5)
==Acknowledgements=={{:Acknowledgements Sanitation}}* Crites, R. and Tchobanoglous, G. (1998). Small and Decentralized Wastewater Management Systems. WCB/McGraw- Hill, New York, US. pp. 355-364. (Book; A short summary of design and construction considerations)
==References * Mara, D. D. (1996a). [https://www.susana.org/en/knowledge-hub/resources-and external links==-publications/library/details/2972 Low-Cost Sewerage]. Wiley, Chichester, UK. (Assessment of different low-cost systems and case studies)
* Azevedo NettoMara, MMD. and Reid, RD. (19921996b). Innovative and Low -Cost Technologies Utilized in SewerageUrban Sanitation. Environmental Health ProgramWiley, Chichester, Technical Series NoUK. 29pp. Pan American Health Organization, Washington DC93-108. (A Short Book; Comprehensive summary and component diagrams-Chapter 5.including design examples)
* CritesOtis, R. J. and TchobanoglousMara, GD. D. (19981985). [https://www.ircwash.org/resources/design-small-bore-sewer-systems The Design of Small and Decentralized Wastewater Management Bore Sewer Systems]. WCB UNDP Interregional Project INT/81/047, The World Bank and McGraw-HillUNDP, New YorkWashington, USAD.C. pp 355–364, US. (A short Comprehensive summary of design , installation and construction considerations.maintenance)
* Mara, DD. (1996). Low-Cost Sewerage. Wiley, Chicheser, UK. (Assessment of different low-cost systems and case studies.)===Acknowledgements=== * Mara, DD. (1996). Low-Cost Urban {{:Acknowledgements Sanitation. Wiley, Chichester, UK. pp 93–108. (Comprehensive summary including design examples.) * Otis, RJ. and Mara, DD. (1985). The Design of Small Bore Sewer Systems (UNDP Interreg. Project INT/81/047). TAG Technical Note No.14. United Nations Development Programme + World Bank, Washington. Available: www.wds.worldbank.org (Comprehensive summary of design, installation and maintenance.)}}
