Sewerage and Sanitary Systems Q7 - Estate Agent's Examination Part 1&2

Q.
Explain three (3) of the following:-

a) Separate system in underground sewerage system

b) One pipe system in building sanitation system

c) Factors to be considered in selecting sanitary appliances

d) The location of manhole in sewerage system

(25 marks, 2012 Q7)

A. This question repeated in 2015 Q7.

(a) Separate system in underground sewerage system.

Similar question was asked in 2015 Q7.

So, for Separate sewers the waste pipe (from Kitchen, Bath Sink) and soil pipe (Sanitary Waste) from the house do not mix with the storm-water pipe. Which means, during heavy downpour, rain water from the stormwater pipe would not overflow. Therefore, surface run-off would not be contaminated with human sanitary waste as they would not mix in the separate sewerage system.

The separate collection prevent the overflow of sewer systems and treatment stations during rainy periods and the mixing of the relatively little polluted surface run-off with chemical and microbial pollutants from the municipal wastewater. The design of the sewers and the (semi-)centralised treatment stations thus needs to consider the volume of the wastewater only and the surface run-off and rainwater can be reused (e.g. for landscaping or agriculture) after a simplified treatment.

Sewer separation has been used to eliminate combined sewer overflows for over 50 years. Today, separate sanitary sewer and storm water systems are more and more common. However, sewer separation is often said to be too disruptive, costly, and may result in an increase in pollutant loading to receiving waters as a result of the increased discharge of untreated surface run-off.

Incomplete sewer separation efforts can also result in poor sanitary sewer system performance, including basement flooding and sanitary sewer overflows (TUIG et al. 2009). Moreover, storm water drains in heavily urbanised areas may receive a variety of pollutants from rooftops, lorry loading bays, industrial sites and even from illegal connections to the surface water system. Therefore, publicity and inspections are needed to ensure that unexpected pollution does not arise from these sources (see also standards or restrictions).

Pollutant loads discharged from urban storm water drainage systems not only vary depending on the urban structure, and the variety of materials entering the sewer network, but also on the local rainfall patterns and the processes of mixing and degradation that occur in the sewers. Hence, careful planning of the sewerage network is required to address these problems. Various modelling tools, such as rainfall modelling, sewer and sewage treatment modelling and river quality modelling, are now available to assist in this planning process (HELMER and HESPANHOL 1997).

Ref:

Separate Sewer. SSWM available at,

http://www.sswm.info/content/separate-sewers

(b) One pipe system.

Similar question was asked in 2012 Q5 here.

1. Ease of cleaning
2. Durability from deformity
3. Style and conformance to general aesthetics of the surrounding

See 2012 Q5, 2015 Q7(c)

(d) Manhole location.

Manhole is provided when

There is change in grade of sewer
There is change in alignment
There is change in size of sewer
At junction of two or more sewers
Manhole is also provided in straight alignment of sewers at regular intervals depending upon the diameters of sewers.