In tropical regions, where most of the developing countries are located, septic tanks and other onsite sanitation systems are the predominant form of storage and pre-treatment of
excreta and wastewater, generating septage and other types of sludges. The septage is disposed of untreated, mainly due to lack of affordable treatment options. This study presents lessons that have been learned from the operation of pilotscale constructed wetlands (CWs) for septage treatment since 1997. The experiments have been conducted by using three CW units planted with narrow-leave cattails (Typha augustifolia) and operating in a vertical-flow mode. Based on the experimental results, it can be suggested that the optimum
solids loading rate be 250 kg TS/m2 yr and 6-day percolate impoundment. At these
operational conditions, the removal efficiencies of CW units treating septage at the range of 80-96% for COD, TS and TKN were achieved. The biosolid accumulated on the CW units to a depth of 80 cm has never been removed during 7 years of operation, but
bed permeability remained unimpaired. The biosolid contains viable
helminth eggs below critical limit of sludge
quality standards for agricultural use. Subject to local conditions, the suggested
operational criteria should be reassessed at the full-scale implementation.
