Field-scale baffled and biorack hybrid constructed wetland: effect of fluctuating loading rates and recirculation for domestic wastewater treatment

Abstract

The conventionally used constructed wetlands require modification/s to minimize clogging problems and space requirement. In this study, a field-scale baffled and biorack hybrid constructed wetland (BBHCW) was developed as a part of 42 KLD decentralized wastewater treatment (DWT) system at Walchand College of Engineering, Sangli (M.S.), India for domestic wastewater. Brickbats were used as support medium in the baffled portion and corrugated sheets in biorack. Mixed vegetation of Typha angustifolia and Canna indica was used in both baffled and biorack portions. BBHCW was operated under the dynamic conditions of flow (0.60–9.89 m³/m² day) and strength (0.12–2.12 kg COD/m² day) for 8 months. The performance was assessed for the removal of organic carbon and nitrogen with and without recirculation of treated effluent. Tracer studies showed that the hydraulic efficiency was satisfactory. COD, BOD₃, and TKN removal is possible to an extent of 26.30 ± 1.36, 29.08 ± 2.43, and 19.39 ± 2.27%, respectively, under dynamic conditions. Recirculation enhances the removal efficiency of COD by 5.00–10.00%. However, TKN removal was not significant with or without recirculation. Morphological study showed that vegetation growth was well supported in BBHCW. The discarded corrugated sheets in BR and brickbats in BSFW are the most appropriate low-cost options. The clogging problem is reduced significantly. BBHCW is sturdy enough to absorb shock loading and space requirement can be reduced by judicious choice of HLR and OLR. BBHCW is an alternative to conventionally used sub-surface constructed wetland as a part of DWT.

Novelty statement

• Development of newly configured baffled and biorack hybrid dual-species constructed wetland (BBHCW) for field scale application.

• Use of discarded brickbat and cement sheets as a new support medium and bioracks.

• Performance assessment of field-scale BBHCW for the removal of organic carbon (expressed as COD and BOD₃), and nitrogen (expressed as TKN) from domestic wastewater under highly dynamic conditions induced by fluctuating hydraulic loading rate (0.60–9.89 m³/m² day) and organic loading rate (0.12–2.12 kg COD/m² day).

Keywords:

• Biorack
• brickbat
• decentralized treatment
• hybrid constructed wetland
• hydraulic loading rate
• organic loading rate

Acknowledgment

This study is a part of research project sanctioned and funded by Department of Science and Technology (DST) under Water Treatment Initiative (WTI) programme. The authors sincerely acknowledge and thank DST for providing financial support to undertake this study.

Disclosure statement

No potential conflict of interest was reported by the author(s).