Investigating the viability and performance of the pilot scale fly ash/lime filter tower for onsite greywater treatment

摘要

The pilot-scale modified fly ash/lime filter tower (FLFT) was tested for treatment of greywater for reuse in irrigation of gardens in five households in Makana Local Municipality, South Africa. The greywater treatment efficiencies for chemical and microbial indicators stabilised after an initial period of 4 weeks. Then the FLFTs were able to remove 62% of the faecal coliform concentrations in the influent and between 20% and 97% of the influent turbidity values. Results of reuse of the FLFT-treated greywater for irrigation in subsistence agriculture indicates that a chlorinator and a drip filter should be installed at the outflow from the FLFT. The mean removal efficiency for the total aerobic bacteria varied between 21% and 88%. Release of anaerobic bacteria from the FLFTs was recorded at all sampling sites, with the particular average values ranging from 11% to 266%. Irrigation with FLFT effluent resulted in slight increase in the soil pH and loss on ignition, no change or slight decrease in the soil particle density. Bulk density of the soil increased or remained constant as a result of irrigation with FLFT effluent. The microbial indicators of soil were not affected by the irrigation with FLFT effluent. Fate of cadmium and aluminium in the FLFT effluent-irrigated soil and plants grown in this study will have to be examined in more detail. The FLFT should be inoculated with denitrification bacteria and its operation must be further investigated for the optimisation of the nitrate removal.