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close this bookA Guide to the Development of on-site Sanitation (WHO; 1992; 246 pages)
View the documentPreface
open this folder and view contentsPart I. Foundations of sanitary practice
close this folderPart II. Detailed design, construction, operation and maintenance
open this folder and view contentsChapter 5. Technical factors affecting excreta disposal
open this folder and view contentsChapter 6. Operation and maintenance of on-site sanitation
open this folder and view contentsChapter 7. Components and construction of latrines
close this folderChapter. 8 Design examples
View the documentIntroduction
View the documentPit latrine design
View the documentSeptic tank design
View the documentAqua-privy design
View the documentDisposal of effluent from septic tanks and aqua-privies
View the documentComposting toilets
open this folder and view contentsPart III. Planning and development of on-site sanitation projects
View the documentReferences
View the documentSelected further reading
View the documentGlossary of terms used in this book
View the documentAnnex 1. Reuse of excreta
View the documentAnnex 2. Sullage
View the documentAnnex 3. Reviewers
View the documentSelected WHO publications of related interest
View the documentBack Cover
 

Disposal of effluent from septic tanks and aqua-privies

Example 8.6

Determine the size of soakpit required in porous silty clay to dispose of the effluent from the septic tank considered in Example 8.5.

From Example 8.5, the sewage flow is 200 litres per day.

From Table 5.4, the infiltration rate for sewage is 20 l per m2 per day.

Therefore, the wall area required is

If the pit is 1.5 m in diameter, then the depth required from the bottom of the pipe from the septic tank to the bottom of the pit is:

Example 8.7

Determine the size of drainage field required in porous silty clay to dispose of the effluent from the septic tank considered in Example 8.4.

From Example 8.4 the sewage flow is 1440 l per day.

From Table 5.4, the infiltration rate for sewage is 20 l per m2 per day.

So the wall area required is

If the effective depth of the trench (the depth from the bottom of the pipe to the bottom of the trench) is 0.6 m, the length of trench required is:

This allows for infiltration on both sides of the trench.

If the plot is large enough, the drainage field should consist of two trenches, each 30 m long, connected in series.

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