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Simplified Sewer

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|english_link=Simplified_Sewers

|french_link=Réseau_d’égout_à_faible_diamètre

[[Image:Icon_simplified_sewers.png |right|80px]]

'''Simplified Sewers describe a sewerage network that is constructed using smaller diameter pipes laid at a shallower depth and at a flatter gradient than conventional sewers. The Simplified Sewer allows for amore flexible design associated with lower costs and a higher number of connected households.'''

Expensive manholes are replaced with simple inspection chambers. Each discharge point is connected to an interceptor tank to prevent settleable solids and trash from entering the '''A simplified sewer. As well, each household should have describes a grease trap before the sewer connection. Another key design feature sewerage network that is that the sewers are constructed using smaller diameter pipes laid within the property boundaries, rather at a shallower depth and at a flatter gradient than beneath the central roadConventional Sewers (C. Because the sewers are more communal, they are often referred to as condominial sewers6). Oftentimes, the community will purchase, and connect to, The simplified sewer allows for a single legal connection to the main sewer; the combined effluent of the condominal sewer network flows into the main sewer linemore flexible design at lower costs.'''

Because Conceptually, simplified sewers sewerage is the same as Conventional Gravity Sewerage, but without unnecessarily conservative design standards and with design features that are better adapted to the local situation. The pipes are usually laid on or around within the property of boundaries, through either the usersback or front yards, higher connection rates can be achievedrather than beneath the central road, allowing for fewer and shorter pipes. Because simplified sewers are typically installed within the condominium, they are often referred to as condominial sewers. The pipes can also be used and less excavation is required as the pipes will routed in access ways, which are too narrow for heavy traffic, or underneath pavements (sidewalks). Since simplified sewers are installed where they are not be subjected to heavy traffic loads. However, this type of Conveyance technology requires careful negotiation between stakeholders since design they can be laid at a shallow depth and maintenance must be jointly coordinatedlittle excavation is required.

All greywater should be connected ===Design Considerations=== In contrast to the Simplified Sewer Conventional Sewers that are designed to ensure adequate hydraulic loadinga minimum self-cleansing velocity, the design of simplified sewers is based on a minimum tractive tension of 1 N/m2 (1 Pa) at peak flow. Inspection chambers also function to attenuate The minimum peak discharges into the systemflow should be 1.5 L/s and a minimum sewer diameter of 100 mm is required. A gradient of 0.5% is usually sufficient. For example, a 100mm diameter 100 mm sewer laid at a gradient of 1m 1 m in 200m (0.5%) 200 m will serve around 200 households of 5 people (102,000 800 users) with a wastewater flow of 80L60 L/person/day.

Although watertight sewers PVC pipes are recommended to use. The depth at which they should be laid depends mainly on the idealamount of traffic. Below sidewalks, covers of 40 to 65 cm are typical. The simplified design can also be applied to sewer mains; they may can also be difficult to achievelaid at a shallow depth, provided that they are placed away from traffic. Expensive manholes are normally not needed. At each junction or change in direction, simple inspection chambers (or cleanouts) are sufficient. Inspection boxes are also used at each house connection. Where kitchen greywater contains an appreciable amount of oil and therefore grease, the sewers should be designed installation of grease traps (see PRE, p. 100) is recommended to take into account the extra flow that may result from stormwater infiltrationprevent clogging.

Blocks of community-based Simplified Sewers are connected Greywater should be discharged into the sewer to an existing [[Conventional Gravity Sewer]] or routed to a Simplified Sewer main constructed with pipes of a larger diameterensure adequate hydraulic loading, but stormwater connectionsshould be discouraged. A Simplified Sewer main can still be placed at a shallow depth providing However, in practice it is placed away difficult to exclude all stormwater flows, especially where there is no alternative for storm drainage. The design of the sewers (and treatment plant) should, therefore, take into account the extra flow that may result from trafficstormwater inflow.

<br>

{{procontable | pro=- Can be built laid at a shallower depth and repaired with locally available materials. <br> - Construction can provide short-term employment to local labourers. flatter gradient than Conventional Sewers <br> - Capital Lower capital costs are between 50 and 80% less than [[Conventional Gravity Sewer]]Sewers; low operating costs are low. <br> - Can be extended as a community changes and grows. | con=<br>- Greywater can be managed concurrently <br>- Requires expert design and construction supervision. Does not require onsite primary treatment units <br> | con=- Requires repairs and removals of blockages more frequently than a Conventional Gravity Sewer. <br> - Requires expert design and construction <br>- Effluent Leakages pose a risk of wastewater exfiltration and sludge (from interceptors) requires secondary treatment groundwater infiltration and/or appropriate discharge.are difficult to identify

}}

===AdequacyAppropriateness===Simplified sewers can be installed in almost all types of settlements and are especially appropriate for dense urban areas where space for onsite technologies is limited. They should be considered as an option where there is a sufficient population density (about 150 people per hectare) and a reliable water supply (at least 60 L/person/day). Where the ground is rocky or the groundwater table high, excavation may be difficult. Under these circumstances, the cost of installing sewers is significantly higher than in favourable conditions. Regardless, simplified sewerage is between 20 and 50% less expensive than Conventional Sewerage.

Where the ground is rocky or the groundwater table is high===Health Aspects/Acceptance=== If well constructed and maintained, the excavation sewers are a safe and hygienic means of trenches for pipes may transporting wastewater. Users must be difficult. Under these circumstances, well trained regarding the cost of installing sewers is significantly higher than in favourable conditions. Regardless, Simplified Sewerage is less expensive than [[Conventional Gravity Sewer|Conventional Gravity Sewerage]] because of its shallow installation depthhealth risks associated with removing blockages and maintaining inspection chambers.

Simplified Sewers can be installed in almost all types of settlements and are especially appropriate for dense, urban settlements. To prevent clogging and maintain the sewers, good pre-treatment is required. It is recommended that the scum from greywater, heavy solids and garbage be removed from the wastewater prior to entering the sewer. ===Health Aspects/AcceptanceOperation & Maintenance=== If constructed andmaintained well, sewers Trained and responsible users are a safe essential to ensure that the flow is undisturbed and to avoid clogging by trash and hygienic means other solids. Occasional flushing of transporting wastewaterthe pipes is recommended to insure against blockages. Users must Blockages can usually be well educated about removed by opening the health risks associated with maintaining/ cleaning blockages cleanouts and inspection chambersforcing a rigid wire through the pipe. ===Upgrading=== Household inspection Inspection chambers can must be upgraded periodically emptied to septic tanks so that fewer solids enter prevent grit overflowing into the Simplified Sewer network, but this will increase maintenance costs associated with emptying the septic tank. ===Maintenance=== Pre-treatment with interceptor tanks and a grease trap is essentialsystem. The homeowner must maintain operation of the system depends on clearly defined responsibilities between the interceptor tanks sewerage authority and the grease trapcommunity. Ideally, households will also be responsible for the maintenance of pre-treatment units and the condominial part of the sewerssewer. However, however in practice this may not be feasible. Alternatively, a private contractor or users committee can be hired to assume responsibility for the maintenance as inexperienced because users may not detect problems before they become severe, and therefore, more costly to repair. A related problem is that households may drain stormwater into the sewer. This practice should be discouraged whenever possible. Blockages Alternatively, a private contractor or users committee can usually be removed by opening the sewer and forcing a length of rigid wire through the sewer. Inspection chambers must be emptied periodically hired to prevent grit overflowing into do the systemmaintenance.

===References===

* Bakalian, A., Wright, A., Otis, R. and Azevedo Netto, J. (1994). Simplified Sewerage: Design Guidelines. UNDP-World Bank Water and Sanitation Program, Washington, D.C., US.

:Available at: [http://documents.worldbank.org/curated/en/home documents.worldbank.org/curated/en/home] (Design guidelines for manual calculations)

* Azevedo NettoMara, MMD. and Reid, RD. (19921996a). Innovative and Low -Cost Technologies Utilized in Sewerage. Technical Series No. 29Wiley, Environmental Health Program. Pan American Health OrganizationChichester, Washington DCUK. (Refer to Chapters 3 and 4 for component diagrams and design formulae.) * Bakalian, A., Wright, A., Otis, R. and Azevedo Netto, J. (1994). Simplified sewerage: design guidelines. Water Assessment of different low-cost systems and Sanitation Report No. 7. The World Bank + UNDP, Washington. (Design guidelines for manual calculations.)case * HABITAT (1986). The design of Shallow Sewer Systems. United Nations Centre for Human Settlements (HABITAT), Nairobi, Kenya. (Detailed design tools and practical examples.studies)

* Mara, DDD. D. (19961996b). Low-Cost Urban Sanitation. Wiley, Chichester, UK. pp 109–139. 109-139. (Comprehensive summary including design examples.)

* Mara, DDD. D. (19962005). Low-Cost Sanitation for All in Periurban Areas? Only If We Use Simplified Sewerage. Wiley, Chichester, UKWater Science & Technology: Water Supply 5 (6): 57-65. (Assessment of different low-cost systems An article summarizing the technology and case studies.its potential rolein urban sanitation)

* Mara, DDD.D., Sleigh, A. and Tayler, et alK. (2001). PC-based Based Simplified Sewer Design. University of Leeds, EnglandLeeds, UK.: Available at: www.efm.leeds. ac.uk/CIVE/Sewerage/ (Comprehensive coverage of theory and design including a program to be used as a design aid.)

* Watson, G. (1995). Good Sewers Cheap? Agency-Customer Interactions in Low-Cost Urban Sanitation in Brazil. The World Bank, Water and Sanitation Division, The World Bank, Washington, DCD.C., US. :Available at: www.wsp.org (A summary of large -scale projects in Brazil.)

===Acknowledgements===

{{:Acknowledgements Sanitation}}

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