Science Target Conference Systems, Ajman 4th International Environment Conference 2016

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Comparative Study of the Domestic Wastewater Treatment with Ponds and Vertical-flow Constructed Wetlands
Sanak Ray, Rawaa Al-Isawi, Miklas Scholz

Last modified: 2015-10-21

Abstract


A comparative study using ponds and constructed vertical-flow wetlands was carried out to assess the nutrient removal efficiency during the treatment of real domestic wastewater to improve environmental health. Common reed was used in both systems, which comprised four different designs each (A to D). Design A compared to design B was used to assess the impact of higher loading rate in terms of chemical oxygen demand (COD). The effect of a lower contact time was tested between designs C and D. Finally, the impact of a lower resting time can be assessed by comparing differences between designs C and D. Three different types of wetlands were tested to identify best practice: ponds with wastewater; ponds with wastewater and reeds; and ponds with wastewater, reeds and aeration. Another objective was to compare the impact of operational (contact time, empty time and COD loading) variables on seasonal performance of wetlands operated in a tidal-flow mode. Compliance with standards was achieved for ammonia-nitrogen, nitrate-nitrogen and suspended solids, and non-compliance concerning biochemical oxygen demand and ortho-phosphate-phosphorus. The system with the highest COD loading performed the best regarding outflow COD concentration. Higher COD inflow concentrations had a significantly positive impact on the treatment performance for COD, ortho-phosphate-phosphorus and suspended solids. Highest nitrate-nitrogen, ammonia-nitrogen, COD and ortho-phosphate-phosphorus removal were observed for aerated ponds in comparison to the other two. Nitrate-nitrogen concentration increased in the aerated ponds due to ammonia oxidation.The highest nutrient removal efficiency was observed for the system with a higher loading rate.