Effect of filter media and hydraulic retention time on the performance of vertical constructed wetland system treating dairy farm wastewater

Abstract

This study deals with the dairy wastewater treatment using laboratory scale vertical flow (VF) constructed wetlands with the <i>Canna indica</i> plantation over wetland beds due to phytoremediation capabilities. Three laboratory scale VF CWs (CW-A, CW-B and CW-C) each with an area of 0.135 m2 filled with gravel (CW-A: 20 mm; CW-B:10 mm gravel) and sand (CW-C) receiving 0.04 m3 d-1 dairy wastewater were operated for the wastewater purification. Each unit was operated at three hydraulic retention times (HRTs) i.e. 12 h, 24 h and 48 h for assessing its effect on wastewater purification . Among all units, removal rates fluctuated as: total suspended solids (TSS): 64.2–74.5%; biochemical oxygen demand (BOD): 45.3 – 63.1%; ammonium nitrogen (NH4–N): 29.6 – 56.5% and phosphate phosphorous (PO4–P): 20.5 – 57.8% at different HRTs. Increase in HRT showed better removal of pollutants in all CWs. Moreover, maximum removal of pollutants excluding TSS and NH4-N was achieved in CW-B at 48 h HRT. CW-B with similar HRT provided maximum removal of PO4-P (57.8%), BOD (63.1%) and chemical oxygen demand (COD): 67.4%. Increase in the size of filter media, from sand (0.25 mm) to 20 mm gravel resulted in higher removal of NH4 -N from wastewater.

Efficient Wastewater Treatment and Removal of Bisphenol A and Diclofenac in Mesocosm Flow Constructed Wetlands Using Granulated Cork as Emerged Substrate

“…HRT plays an important role as it affects the contact duration between pollutants and microbes [ 69 ]. The removal rates of the different systems continued to increase significantly with the HRT increase (from 6 h until 48 h).…”

Growth of floating hook-moss (Warnstorfia fluitans) differs with nutrient and water flow adjustments in greenhouse and cold room conditions

“…We initially expected that the nutrient uptake is affected by the rate of water flow, because flow rate and hydraulic retention time affect uptake efficiency of nutrients in wetlands, in general [ 36 , 37 ]. The water flow rate in our experiment was observed to have an effect on the growth rate.…”

Phytoremediation: A Shift Towards Sustainability for Dairy Wastewater Treatment

“…In a phytoremediation system, the hydraulic retention time (HRT) represents the time of interaction between wastewater and the phytoremediation system, that has a significant impact on the performance of the system. According to earlier research, more the duration of contact with water and filter material inside the wetland results in higher contaminant removal [84]. Additionally, systems which provide a larger contact surface for the microbes to adhere to, promotes efficient reduction within the required treatment time.…”

“…Numerous microorganisms, including Bacillus, Micrococcus, Pseudomonas, and others, use these filter materials as a natural habitat to degrade organic matter and promote nitrification and denitrification. These filter materials work effectively to remove contaminants from wastewater, including faecal coliforms, BOD, COD, ammonium (NH 4 -N), and phosphate ions (PO 4 -P) [84].…”