Wastewater management is a prior concern to ensure an acceptable living standard in Nepalese prisons as most of them are old, overcrowded and lack treatment facilities.
Usually, raw wastewater from prisons is combined with the municipal drainage and is discharged into the nearby river or stream. As a result, the surface water quality in urban Nepal is getting down with an increase of eutrophic and anoxic conditions.
In urban Nepal the centralised wastewater treatment systems were more commonly applied in the past. However, due to lack of technical expertise, higher operational and maintenance cost, and expensive spare parts, these centralised facilities are either not functional or less efficient.
In recent times the small scale decentralised system, particularly the constructed wetland, is gaining popularity due to cost effectiveness and minimal maintenance.
Moreover, there is also a chance to enhance the ecological diversity.
Though, a number of wetland systems are working in Nepal, they are mainly designed for the organic load removal since nutrients reduction is still not a high priority. The design is mainly based on Kickuth (1984), which is mainly relevant for small systems.

This study has given an equal importance for the removal of both nutrients and organic load while designing a constructed wetland system for Biratnagar regional jail, in Nepal. The wastewater from this prison is being discharged to the nearby river (Singhiya khola) together with the municipal drainage without any treatment. Hence, the problem of Biratnagar regional jail has been considered as a representative case and different design methods were applied to identify the best dimensions of wetland systems to remove both nutrients and organic loads to a desired minimum level.

The research showed that the design of the wetland system based on Kadlec and Knight (1996) was more economic to treat both nutrients and organic loadings when compared to the wetland size given by other three methods (Reed et.al, 1995; Crites and Tchobanglous, 1998; and Kickuth, 1984). In the mean time it was also confirmed that a combination of wetland systems working in parallel and preceded by SSF over the FWS is more robust than it was configured in reverse order (FWS ahead of SSF). The proposed wetland system seemed quite efficient with design performance of, 86% BOD, 83% TSS, 65% TN, and 60% NH4 removal. However, the removal of TP was lower, with 33% reduction only. It was further confirmed that the reduction of TP can not be increased by enlarging the wetland area only. The substrate type and its adsorption capacity are other factors to be considered while designing the constructed wetland for removing TP.

For the primary treatment, an anaerobic pond was found more appropriate because of its lower capital and operating cost. It was expected to remove at least 40 % of BOD and 30 % of TSS from the raw waste water. Further, this research aimed to develop an insight on ecological enhancement during different levels of treatment in the wetland system. A comparative study of ecological development on the basis of macro-invertebrate taxa, carried out in Ichtegem (Belgium) confirmed that the wetland system provides a suitable habitat for a biodiverse macroinvertebrate community. Though the diversity was largely dominated by pollution resisting taxa like Chironomidae, Dystiscidae or Corixa, some taxa more sensitive to pollution like Ischnura and Cloeon were also present in the wetland system. Compairng different sampling method learned that more taxa were present with artificial substrates than using the hand net sampling method in the HFRB.

Both ecological indices BBI and MMIF showed that the quality of water is improving from very bad to moderate while following different stages of treatments via wetlands. In this way the constructed wetland system proved to be a promising technology to reduce pollutants and improve the ecological quality of water.
 

Promoters
Prof. dr. ir. Peter Goethals
dr. ir. Erik Meers
Tutor
MSc. Pieter Boets