Abstract
Large amounts of construction and demolition (C&D) waste have been generated due to the rapid urbanization process in China over recent decades. Hence, effective strategies for C&D waste reuse and recycling are urgently needed to reduce the impact of the generation of C&D waste. This work assessed the pollution control efficiency of recycled aggregates from C&D waste as substrates in vertical flow constructed wetlands (VFCWs) and the regeneration capability of these substrates. Six artificial experimental columns loaded with three recycled aggregates, namely, brick (RBA), concrete (RCA), and concrete-brick mixtures (C&B), and three natural aggregates, namely, limestone (LIM), lava rock (LAV), and zeolite (ZEO), were separately used. The results showed that recycled aggregates performed more effectively in terms of TP and COD removal than did natural aggregates, with the highest removal efficiency of 87.1% towards TP achieved by RCA and 74.9% towards COD achieved by C&B. Nemerow pollution index calculation demonstrated that the effluent water quality followed the order of RCA > C&B > RBA > LIM > ZEO > LAV. NH3–N, TP and COD removal efficiencies of 51.3%, 51.0% and 58.9%, respectively, were observed for RCA after in situ regeneration. The highest NH3–N and TP removal efficiencies were 54.7% and 84.8%, respectively, for RCA by aeration and NaOH washing, respectively, after four adsorption-desorption runs of ectopic regeneration. However, chemical regeneration of RCA and LIM severely destroyed the substrate structure over physical regeneration. Unfortunately, a low temperature led to a poor removal of TN in all systems, and the recycled aggregates from C&D waste were less resistant to impact than were the natural aggregates. Life cycle cost analysis showed that RCA as a substrate reduces the cost of wetland construction. This work provides a systematic comparison of recycled aggregates and natural aggregates as substrates in VFCWs in regard to their purification ability, regeneration methods and economic cost.
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