Field scale evaluation of seasonal wastewater treatment efficiencies of free surface-constructed wetlands in ICRISAT, India uri icon

abstract

  • The disparity between volume of wastewater generatedand treated has resulted in severe water pollutionand eutrophication of the water bodies in most Indiancities. Constructed wetlands (CWs) present a low-costwastewater treatment option; however, field scale studieswith real life wastewater are limited. Eichhorniacrassipes (water hyacinth), Typha latifolia (Typha) andPistia stratiotes (water lettuce) grow abundantly ineutrophicated water bodies, and are known for theirnutrient uptake ability. In the present study, the wastewaterof a nearby urban residential colony was treatedby two-field scale free water surface CWs operatingunder identical hydraulic loading. The first treatmentcells, in each of these two CWs were vegetated withTypha. The second treatment cells were vegetated withwater hyacinth (CW-1) in one of the CWs and withwater lettuce (CW-2) in the other. Wastewater treatmentefficiencies of these free water surface CWs wereevaluated, in terms of the removal efficiencies for keyparameters, viz. chemical oxygen demand (COD),ammoniacal and nitrate nitrogen, phosphate, sulphateand total suspended solids (TSS). The CW-1 showedgreater seasonal variation in performance. A steadyremoval efficiency of 35?40% was observed forammoniacal nitrogen in both the free water surfaceCWs throughout the year, though removal efficiencyof nitrate nitrogen reduced significantly during thewinter. Plant sample analysis showed that the N, Pand K uptake capacities of water lettuce were 1.53,1.55 and 1.34 times higher than that of water hyacinth,for identical wastewater loading. The dryweight of the harvested biomass for water lettuce, duringsummer months, was much higher at 5.63 g/m2/dcompared to 3.8 g/m2/d for water hyacinth

publication date

  • 2016
  • 2016