Pilot-scale hybrid constructed wetlands for the treatment of cooling tower water prior to its desalination and reuse

Thomas V Wagner; Vinnie de Wilde; Bert Willemsen; Muhamad Mutaqin; Gita Putri; Julia Opdam; John R Parsons; Huub H M Rijnaarts; Pim de Voogt; Alette A M Langenhoff

doi:10.1016/j.jenvman.2020.110972

Pilot-scale hybrid constructed wetlands for the treatment of cooling tower water prior to its desalination and reuse

J Environ Manage. 2020 Oct 1:271:110972. doi: 10.1016/j.jenvman.2020.110972. Epub 2020 Jun 24.

Affiliations

¹ Institute for Biodiversity and Ecosystem Dynamics (IBED), University of Amsterdam, P.O. Box 94248, 1092 GE, Amsterdam, the Netherlands; Department of Environmental Technology, Wageningen University, P.O. Box 17, 6700 EV, Wageningen, the Netherlands. Electronic address: thomas.wagner@wur.nl.
² Department of Environmental Technology, Wageningen University, P.O. Box 17, 6700 EV, Wageningen, the Netherlands.
³ Institute for Biodiversity and Ecosystem Dynamics (IBED), University of Amsterdam, P.O. Box 94248, 1092 GE, Amsterdam, the Netherlands.
⁴ Institute for Biodiversity and Ecosystem Dynamics (IBED), University of Amsterdam, P.O. Box 94248, 1092 GE, Amsterdam, the Netherlands; KWR Water Research Institute, Chemical Water Quality and Health, P.O. Box 1072, 3430 BB, Nieuwegein, the Netherlands.

PMID: 32579525
DOI: 10.1016/j.jenvman.2020.110972

Abstract

Cooling towers are responsible for a large part of the industrial fresh water withdrawal, and the reuse of cooling tower water (CTW) effluents can strongly lower industrial fresh water footprints. CTW requires desalination prior to being reused, but various CTW components, such as total organic carbon (TOC), conditioning chemicals and total suspended solids (TSS) hamper physico-chemical desalination technologies and need to be removed from the CTW. A cost-efficient and robust pre-treatment is thus required, which can be provided by constructed wetlands (CWs). The present study is the first study that determined the CTW pre-treatment efficiency of hybrid-CWs and the impact of winter season and biocides in the CTW on the pre-treatment efficiency. The most efficient CW flow type and dominant removal mechanisms for CW components hampering physico-chemical desalination were determined. Subsurface flow CWs removed PO₄^3-, TSS and TOC as a result of adsorption and filtration. Vertical subsurface flow CWs (VSSF-CW) excelled in the removal of benzotriazole as a result of aerobic biodegradation. Horizontal subsurface flow CWs (HSSF-CW) allowed the denitrification of NO₃^- due to their anaerobic conditions. Open water CWs (OW-CWs) did not contribute to the removal of components that hamper physico-chemical desalination technologies, but do provide water storage options and habitat. The biological removal processes in the different CW flow types were negatively impacted by the winter season, but were not impacted by concentrations of the biocides glutaraldehyde and DBNPA that are relevant in practice. For optimal pre-treatment, a hybrid-CW, consisting of an initial VSSF-CW followed by an OW-CW and HSSF-CW is recommended. Future research should focus on integrating the hybrid-CW with a desalination technology, e.g. reverse osmosis, electrodialysis or capacitive ionization, to produce water that meets the requirements for use as cooling water and allow the reuse of CTW in the cooling tower itself.

Keywords: Benzotriazole; Biocides; Nitrate; Phosphate; Removal mechanisms; Winter season.

MeSH terms

Waste Disposal, Fluid
Wastewater
Water
Water Pollutants, Chemical / analysis*
Water Purification*
Wetlands

Substances

Waste Water
Water Pollutants, Chemical
Water