Abstract
This study evaluated the performance of horizontal flow constructed wetlands for secondary domestic wastewater treatment, using lightweight aggregates (LWA) as upper substrate. The use of LWA allowed average removal rates of 31–44, 55–69, and 34–43% for total phosphorus, chemical oxygen demand, and total nitrogen, respectively. No significant decline in removal efficiency was observed during the monitored period. After operation for 19 months, in total 4.19–4.61 kg/m2 of organic matter was accumulated and annual solids accumulation rates ranged from 5.3 to 6.0 kg dry matter/m2 per year. High porosity (46%) and specific surface area (11.89 m2/g) of LWA favored to a slight reduction (6.8–13.6% of initial value) of hydraulic conductivity in both systems. Overall, results showed that LWA can be used as candidate materials in engineered wetlands and has a potential of longer lifetime.
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