Integrated faecal sludge treatment and recycling through constructed wetlands and sunflower plant irrigation.
Faecal sludge (FS) from the on-site sanitation systems is a nutrient-rich source but can contain high concentrations of toxic metals and chemicals and infectious micro-organisms. The study employed 3 vertical-flow CW units, each with a dimension of 5 x 5 x 0.65 m (width x length x media depth) and planted with cattails (Typha augustifolia). At the solid loading rate of 250 kg total solids (TS)/m(2).yr and a 6-day percolate impoundment, the CW system could achieve chemical oxygen demand (COD), TS and total Kjeldahl nitrogen (TKN) removal efficiencies in the range of 80-96%. A solid layer of about 80 cm was found accumulated on the CW bed surface after operating the CW units for 7 years, but no clogging problem has been observed. The CW percolate was applied to 16 irrigation sunflower plant (Helianthus annuus) plots, each with a dimension of 4.5 x 4.5 m (width x length). In the study, tap water was mixed with 20%, 80% and 100% of the CW percolate at the application rate of 7.5 mm/day. Based on a 1-year data in which 3 crops of plantation were experimented, the contents of Zn, Mn and Cu in soil of the experimental plots were found to increase with increase in CW percolate ratios. In a plot with 100% of CW percolate irrigation, the maximum Zn, Mn and Cu concentrations of 5.0, 12.3 and 2.5 mg/kg, respectively, were detected in the percolate-fed soil, whereas no accumulation of heavy metals in the plant tissues (i.e. leaves, stems and flowers) of the sunflower were detected. The highest plant biomass yield and oil content of 1000 kg/ha and 35%, respectively, were obtained from the plots fed with 20% or 50% of the CW percolate.
Koottatep
T
T
School of Environment, Resources and Development (SERD) Asian Institute of Technology (AIT) PO Box 4 Klong Laung, Pahtumthani 12120, Thailand. thamarat@ait.ac.th
Polprasert
C
C
Hadsoi
S
S
D004787:Environmental Pollution / Q000517:prevention & control*; D005243:Feces; D006368:Helianthus / Q000254:growth & development; D006801:Humans; D010865:Pilot Projects; D012639:Seeds / Q000502:physiology; D012722:Sewage / Q000032:analysis*; D013785:Thailand; D053833:Wetlands
D012722:Sewage