VOLUME 16, NUMBER 2, 2022, xx–xx RESEARCH ARTICLE Study of chromium removal from wastewater using SSF-CW model: comparison between physical adsorption by coal CFA and phytoremediation by vetiver grass (Vetiveria Zizanioides L) Titik Indrawati 1 , Sarto 1 , Agus Prasetya 1,* 1 Department of Chemical Engineering, Universitas Gadjah Mada, Jl. Grafka 2,Yogyakarta, 55281, Indonesia Received 25 October 2021; revised 9 December 2021; accepted 14 December 2021 OBJECTIVES The study aims to compare the efectiveness of chromium removal from water using adsorption by coal fy ash (CFA) and phytoremediation by vetiver grass (Vetiveria zizanioides L) as well as a combination of both CFA and vetiver grass. METHODS The experiment was carried out in four dif- ferent reactors, having size of 100 cm (length) x 60 cm (wide) x 80 cm (height). One reactor was filled with gravel and CFA, without vetiver grass (RI), while another one was filled with gravel and vetiver grass, without CFA (RIV). The other two re- actors were filled with gravel, CFA, and vetiver grass with the mass ratio of gravel/CFA of (25:2) and (25:1), denoted as RII and RIII, respectively. Fifty (50) L of synthetic wastewater contain- ing 14.612 ppm of chromium was filled into the reactors and continuously re-circulated for 15 days. Chromium accumula- tion in CFA and plants was analyzed on day 15. RESULTS The results of plant development are indicated by the presence of new shoots and roots that grow during phytoremediation processes. In addition, there was an increase in weight and number of vetiver stems indicating the persistency of vetiver grass in such a harsh wastewater condition. The removal of Cr from wastewater in RI, RII, RIII and RIV at days 15 were 81%, 93.2%, 85.8% and 75.7%, respectively. CONCLUSIONS it can be concluded that: (1) vetiver grass (Vetiveria zizanioides L) has high potential as phytoremediator plant, (2) Chromium adsorption by CFA plays important role in Cr removal from wastewater, and (3) combination of adsorption by CFA and a phytoremediation by vetiver grass significantly increases the removal of chromium from wastewater. KEYWORDS adsorption; vetiver grass (Vetiveria Zizanoides L); chromium removal; coal CFA (CFA); phytoremediation; sub surface fow constructed wetlands (SSF-CW) 1. INTRODUCTION Wastewater is the residue from industrial processes, house- holds, laboratories, or offices that have experienced quality degradation due to the presence of hazardous materials. Be- sides industrial wastewater, laboratory wastewater contain- ing heavy metals such as chromium must be treated before being discharged into the water because of its toxicity. Lab- oratory wastewater is characterized by its dynamic distribu- tion and content and its long impact. The quality of wastewa- ter is infuenced by the volume of wastewater, the content of pollutants, and the frequency of waste disposal. The quantity of laboratory wastewater is considered small, while the con- tent of pollutants is varied and some even contain hazardous waste (Said 2008). The source of laboratory wastewater are chemicals solutions used for experiments or testing such as sulfuric acid (H 2 SO 4 ), potassium dichromate (K 2 Cr 2 O 7 ), mer- cury sulphate (Hg 2 SO 4 ), ferro ammonium sulfate (FAS), fer- roin, etc. Chromium in laboratory wastewater can be in the form of Cr 3+ (Cr(III)) and Cr 6+ (Cr(VI)). The presence of high chromium in laboratory wastewater can cause environmen- tal pollution and have a bad impact on health (Melyta et al. 2019). Cr toxicity is highly dependent on its oxidation form and Cr(VI) is more toxic than Cr(III) for plants, animals, and microorganisms. High Cr(VI) concentrations have signifi- cant harmful efects on human health including lung, cancer, kidney, liver, and gastric damage (Sultana et al. 2014). Wastewater treatment technology can be carried out by biological, chemical, and physical processes, which are based on the characteristics of the compounds contained in wastewater. For waste containing heavy metals such as gold mining processing waste, of course, biological treat- ment is not the first choice. This is because the existing heavy metals can poison the microorganisms used (Fadlilah et al. 2018). Subsurface Flow Constructed Wetlands (SSF-CW) is a promising alternative wastewater treatment technology that is built and designed based on the involvement of aquatic plants, soil, or other media and microbes. It is a simple and *Correspondence: aguspras@ugm.ac.id © The Author(s) 2022, under the terms of a CC BY-SA 4.0 license.