ประภา โซ๊ะสลาม. Application of Constructed Wetland for Food Processing Wastewater. Doctoral Degree(Environmental Technology). King Mongkut's University of Technology Thonburi. : King Mongkut's University of Technology Thonburi, 2006.
Application of Constructed Wetland for Food Processing Wastewater
Abstract:
Subsurface flow wetlands typically give better efficiency than surface flow for the same size; however surface flow
systems can handle larger wastewater volumes. This study evaluated increasing water levels in a subsurface flow
three water levels; a) 10-cm below the media, b) equal to the media and c) 10-cm above the media under five, four
and three days of hydraulic retention time (HRT). Typha augustifolia was planted in a microcosm wetland and cassava
starch wastewater was employed as influent. Pollutant removal efficiencies were not significantly different for all
water levels. Evaluated BOD5 removal efficiencies observed were 95.2-96.8 percent for all water levels and HRTs.
Total suspended solid and Total Kjeldahl Nitrogen (TKN) removal efficiencies were 88.9-97 percent and 59.3-79.2
percent for all water levels and HRT. Conclusion of a settling zone was implemented near the inlet to enhance TSS s
eparation and organic decomposition. TSS was rapidly reduced after passing the settling zone at all HRTs. Settling
zone establishment could significantly remove 89.7-93.4 percent of TSS prior to the wastewater entering the root zone.
This can increase all pollutants removal performance.
Six emergent plant species; Cyperus involucratus, Canna siamensis, Heliconia spp., Hymenocallis littoralis, Typha
augustifolia and Thalia dealbata J.Fraser) were conducted. They were fed with seafood wastewater that was 50 percent
diluted with treated seafood wastewater from an aerated lagoon. All macrophytes were found to meet satisfying treatment
efficiency at 5 days hydraulic retention time (HRT). While Cyperus involucratus, Thalia dealbata J.Frazer and Typha
augustifolia met acceptable treatment efficacy at 3 days of HRT. Nutrient uptake rate of these species was observed in
the range of 1.43 -2.30 g Nitrogen/m2.day and 0.17-0.29 g Phosphorus/m2.day, respectively. The highest pollutants
removal performances were found at 5 days HRT. Average removal efficiencies were 91-99 percent for BOD5, 52-90
percent for SS, 72-92 percent for TN and 72-77 percent for TP. Plant growth and nitrogen assimilation were experienced
to be most satisfactory for Cyperus involucratus, Thalia dealbata J.Frazer and Typha augustifolia. Nitrogen and phosphorus
accumulated in plant tissue was associated with plant biomass production. Lower HRTs affected contaminant removal
efficiency and nutrient accumulation in plant tissue for all species. Increase of nutrient accumulation in sediment, water
body and gravel media was also observed. Nitrogen distribution was found to be in the range of 2.17-43.80 percent,
7.91-27.75 percent, 19.62-36.86 percent and 14.39-31.88 percent in plant tissue, treated wastewater, sediment and media,
respectively. Phosphorus distribution can be accounted in the range of 0.79-17.01 percent, 20.35-28.37 percent, 40.96-56.27
percent and 9.09-20.47 percent in plant tissue, treated wastewater, sediment and media, respectively.
The high strength wastewater was also studied in wetland system at different organic loading rates (OLR) of 612, 696, 806, 929
and 1213 kg BOD5/ha.day. The high performance plant species as Cyperus involucratus, Typha augustifolia and Thalia dealbata
J.Fraser were studied. An increase of OLR affected pollutants removal efficiency and plant growth. Tested species may not be
able to bear extensive under the high organic loading rate. Final plant dry weight was lower than the initial while ORL was
increased up to 806 kg BOD5/ha.day. The acceptable pollutant removal efficiency was found at lowest OLR of 612 kg
BOD5/ha.day except for COD removal because input COD was very high. Pollutants reduction were 89-92 percent for SS,
74-89 percent for BOD5, 15-68 percent for COD, 10-81 percent for ammonium, 95-99 percent for nitrate and 21-74 percent
for color reduction, respectively.