Abstract
Three hybrid wetland systems were studied for organics and nutrients removal from synthetic wastewater recipe. Each system included a vertical flow (VF) followed by a horizontal flow (HF) wetland. The wetlands were filled with common and unconventional media (gravel, biochar and sand) with different saturation and water depth ratio. Input N, P and COD loadings ranged between 48–145, 1–7 and 56–191 g/m2 d, respectively across first stage VF wetlands. Recalcitrant compounds of synthetic recipe reduced organics removals in VF wetlands. NH4-N adsorption and carbon leaching properties of biochar triggered N removals (19–102 g/m2 d) in partially saturated VF wetlands. Carbon unavailability influenced N removals in gravel based unsaturated VF wetland. Input N load increment reduced nitrification and NH4-N adsorption in VF wetlands. However, such increment improved N removal percentages in shallow water depth second stage HF wetlands, primarily due to removals in previous stages and atmospheric oxygen transfer via unsaturated zone; HF wetland with deep water depth showed opposite removal trend. P removal in experimental wetlands was achieved via media based adsorption; decrease of P concentration in synthetic recipe enhanced removals. N and P contents percentage (with respect to total removal) in plants ranged between 1 and 7% (VF), 5–17% (HF) and 2–36% (VF), 23–35% (HF), respectively, indicating dominance of microbial transformation and media based adsorption on observed removals. Partially saturated-shallow water depth hybrid wetland systems achieved ≥90% BOD, ≥97% N and 100% P removals. This study signifies potential application of partially saturated-shallow water depth hybrid wetland systems packed with unconventional media for wastewater treatment.
Published Version
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