Constructed Wetlands and Planted Sludge Drying Beds for Decentralized Integrated Wastewater Management.

Wastewater management by large centralised systems has proven to be expensive and difficult to operate in poor countries like Nepal. Constructed Wetlands (CW«s) are a wastewater treatment alternative that is simple in operation and cheap to construct using local means. The robustness and low maintenance requirements makes such systems suitable for decentralized, community managed wastewater treatment. The performance of operating CW«s in Nepal indicate that they are able to reduce the organic pollutant load as well as the nutrients to an acceptable level. Constructed wetlands and sludge drying reed beds (SDRB) can be integrated to treat both wastewater and sludge. In order to develop design criteria for the CW«s and SDRB«s in Nepal two pilot scale experiments were conducted. One tested the performance of horizontal flow (HF) and vertical flow (VF) CW«s for wastewater treatment and compared planted and unplanted systems. The other experiment tested the performance of planted and unplanted sludge drying reed beds. In both experiments the planted beds performed better than the unplanted beds. For wastewater treatment the VF beds, or planted sand-filters, performed better than the HF beds. To meet Nepalese discharge standards HF beds are sufficient, but to meet stricter requirements a combination of HF and VF beds are recommended.