– No. 2 2013,
H. M. K. S. Bandara and M. M. M. Najim
Urban centers are highly significant with limited space together with the rising urban population.
Most of the houses and buildings are attached with some kind of
a sewage disposal facility as central sewage disposal systems are limited.
Urbanization is expected to create many problems in terms of black water disposal
due to limitation of land. A study was done in Gampaha municipality area, an
urban center, where there is no central sewage treatment facility. The objectives of
the study were to analyze the current situation of the black water disposal system in
the study area and to identify the shortcomings of the black water disposal system comparing with the standards.
The study was conducted within the urban center in
five GN divisions. Random samples of 44 households were selected to represent all
the five GN divisions. Selected households were interviewed to collect basic data
needed and physical measurements were also taken where necessary. The data
categories collected are household information, toilet type and size, desludging
interval and distance to nearest well. The code of practice for the design and
construction of septic tanks reports that 80% of urban communities use septic tanks
for sewage disposal, but this study reveals that only 18% of the population uses
septic tanks. Over 82% uses typical soakage pits that are constructed with loosely
constructed brick walls and bare bottom open to soil for their sewage disposal.
Over 68% of the households have their toilet pits within 15m to the nearest well,
which is below the recommended distance. Only 30% of the households comply with
over 15m to the nearest well that is recommended for septic tanks. The
recommended distance for the soakage pits to the nearest well is 30m and only 9%
of the households meet this standard. The black water disposal pits are over sized in
general, so that the desludging interval is more than 10 years. Recently constructed
houses, due to limitation of space, have reduced the size of the pits reducing f desludging interval.
The construction and placement of septic tanks or soakage pits in the area have not complied with the standards.