The Option of Appropriate System for Wastewater Treatment in Low-Density Areas

Abstract

The method for selecting the appropriate treatment system in low-density areas was studied by statistical data analyses and questionnaire surveys. The main results obtained are as follows.(l) The efficiency of sewerage service has been decreasing. With decrease of the population density in served areas, treatment cost is increasing from 7,000 yen/household in 1961 to near 40,000 in 1989.(2) By considering the external cost of treated water quality, the marginal house density beyond which collective systems become advantageous, was estimated to be 9.5 houses/ha compared to the original value of 13 houses/ha.(3) Improvement of water quality, saving energy, and efficient uses of sludge are considered to be important for the environmental impact of sewerage systems. Suitable allocation of optional treatment systems, energy saving technology and prevention of sludge contamination must be the important issues for the sewerage service on a small scale.

Assessing Wastewater Management in the Developing Countries of Southeast Asia: Underlining Flexibility in Appropriateness

“…In terms of community size, Kamal et al [9] defined DWT systems as able to service 1-100 households while Libralato et al [15] described CCT systems as able to service 4-12 houses. Cluster wastewater technology systems are also commonly classified under CWT systems by several researchers [16][17][18][19][20][21]. While these definitions may hold within their context, we have opted to provide our own definition for each technology system to facilitate our discussion.…”

“…Cluster wastewater technology systems exhibit the finer points of both CWT and DWT systems including a lower cost of construction for the sewer network and an easier management of the treatment facility. Communities opt to introduce CCT systems in cases where wastewater treatment can no longer be addressed by DWT systems but are not economically or physically capable of installing full-scale centralised wastewater treatment facilities [21]. The operation and maintenance of the treatment facility is still challenging even though the construction of the sewer network is minimised.…”