Evaluation of ecotechnology performance in treating textile wastewater: constructed treatment wetlands and natural adsorbents

The development of environmentally friendly technology for water ecosystem rehabilitation has become a challenge in solving pollution control problems in water bodies. Ecotechnology is a technology to improve water quality using an ecosystem approach, including the technology of constructed treatment wetlands and natural adsorbents. This study aims to produce an alternative ecotechnology for textile industrial waste remediation, on-site treatment of water bodies contaminated with textile waste, using a constructed treatment wetlands system and natural adsorbents. The result was conducted for 6 months using a reactor on a pilot scale with a continuous system. The result showed that CTWs’ ability effectively reduced ammonia in textile wastewater with a 20% dilution of up to > 80% and > 90% respectively using plants Vetiveria zizanioides and Heliconia psittacorum. Meanwhile, at 50% textile wastewater dilution, CTW with Heliconia psittacorum was more effective in reducing ammonia (> 80%) than CTW with Vetiveria zizanioides (> 60%). CTW with Vetiveria zizanioides and Heliconia psittacorum was able to reduce the dye content up to < 69.68% and < 54.39%, respectively. The natural adsorbent ability of bentonite has a higher ability to reduce dyes and ammonia, which is up to < 64.84% and < 91.12%. Good performance in these two eco-technology systems will result in better waste disposal by combining these two systems into one ecotechnology system.


Introduction
The challenges and problems of controlling indirect and direct pollution in water bodies that are increasingly complex require the development of environmentally friendly water ecosystem rehabilitation technologies.The application of chemicals in overcoming the pollution of polluted water bodies has an impact on the ecological integrity of aquatic ecosystems and generally only solves problems in the short or temporary term.Constructed treatment wetlands (CTWs) are on-site technologies on the mainland in border areas and riparian waters to reduce pollutant loads before they 1260 (2023) 012048 IOP Publishing doi:10.1088/1755-1315/1260/1/012048 2 enter water bodies.Rehabilitation technology innovation with an eco-technology approach continues to be developed.Plants and planting media equipped with media that function as filtration, adsorbents, or substrates for attaching biofilms, can increase the ability of plants to remove various kinds of organic pollutant loads and nutrients from industrial and domestic waste.
The Citarum River is heavily polluted by domestic waste, agricultural runoff, and the textile industry.The river border/riparian area that functions as an ecological and natural repair system is currently in a damaged condition due to human activities.River rehabilitation in border/riparian areas aims to improve water quality and reduce pollutant loads.Technological innovations for the rehabilitation of water resources ecosystems continue to be developed, and ecosystem-based technologies have high potential in their application.Constructed treatment wetlands (CTWs) and natural adsorbents are a combination of physical, chemical, and biological processes often developed to control the pollution of water bodies.The CTWs tested were a horizontal subsurface flow system equipped with coarse gravel, medium-sized gravel, and sand that functioned as adsorbent/filtration as well as Vetiveria zizanioides and Heliconia psittacorum; as well as natural adsorbents such as bentonite and zeolite with a horizontal flow system.There have been a few studies on CTW systems that use Heliconia psittacorum for removing heavy metals [1], aquaculture effluent in a number of free surface flow CTW systems [2], and municipal waste as a secondary treatment in a hybrid CTW system [3,4,5,6].Although mostly studied in a secondary treatment for greywater and municipal wastewater, a horizontal subsurface flow constructed wetland (HFCW) system has been found to have moderate to high removal efficiency (RE) of TSS, COD, TN, TP, ammonia, and nitrate.
The study aimed to test the system performance and removal efficiency of pollutants in textile wastewater.System performance was tested against dyes, and other common pollutants in the form of COD, nutrients, and total suspended solids (TSS).The research also aims to test various alternative modifications in ecotechnology that are most effective for the removal of pollutants in textile wastewater.

Horizontal subsurface flow constructed treatment wetland (HSSF-CTW) system
2.1.1.HSSF-CTW system with Vetiveria zizanioides.Three microfiber cells with 1.0 x 0.60 x 0.4 meters (LxWxD) dimensions were used to build up a horizontal subsurface flow constructed treatment wetland (HSSF-CTW) system.Each cell includes pea gravel, sand, and coarse gravel with porosity of 30%, 50%, and 50%, respectively.A slight layer of mixed soil and compost media was added to the media's surface before a seedling of Vetiveria zizanioides was planted on it.The three cells were positioned parallel, sequentially, and connected to each other to flow the wastewater from cell 1 to cell 3. Wastewater from the tank flows continuously to tanks 1, 2, and 3 (Figure 1).

HSSF-CTW system with Heliconia psittacorum.
In a microfiber cell with dimensions of 2.0 x 0.98 x 0.60 meters (LxWxD), a horizontal subsurface flow developed treatment wetland (HF-CTW) system was installed.Using a perforated plastic block, the cell was divided into three sections and filled with coarse gravel (porosity of 30%), pea gravel of 40%, and sand of 50%.A thin layer of mixed soil and compost media was added to the media's surface before planting a healthy seedling of Heliconia psittacorum.Each portion had measurements of 0.60 x 0.98 x 0.45 meters (LxWxD), which gave a bed volume of 0.32 m 3 overall.SF-CTW configuration is represented in Figure 2.With a flow rate (Q) of approximately 0.12 m 3 /day, effluent is fed into the two HSSF-CTW systems mentioned above, resulting in hydraulic retention times (HRT) (τ) of 2.7 days and hydraulic loading rates (HLR) of 0.07 m/day.

Adsorbents system.
The adsorption process was carried out using a reactor with 0.765 x 0.535 x 0.455 meters dimensions.Each reactor is filled with adsorbent with dimensions of 0.46 x 0.535 x 0.40 meters.In the adsorbent system, the average total residence time was 1 -2 days, the flow type is horizontal with the water surface below the surface of the adsorbent.Specifications for bentonite with a surface area of 24.054 m 2 /g, pore volume 0.078 cm 3 /g, pore size 10.980 nm, micropore volume 0.010 cm 3 /g.Specification for zeolite with a surface area of 17.851 m 2 /g, pore volume of 0.069 cm 3 /g, pore size of 16.978 nm, and micropore volume of 0.008 cm 3 /g (Figure 3).

Sampling and laboratory analysis.
The experiment lasted six months, from June to December 2021.Every week, the influent and effluent were collected from the faucet.A Water Quality Meter (Lutron) was used to immediately measure the temperature, dissolved oxygen (DO), pH, and conductivity in the influent and effluent.Every two days, physicochemical parameters were measured directly.Spectrophotometric methods were used to test dyes, ammonia, nitrate, phosphate, total nitrogen (TN), total phosphorus (TP), and chemical oxygen demand (COD).Total suspended solids (TSS) were measured using a gravimetric method after samples were filtered using GF/A filter paper (Whatman).All laboratory analysis processes were carried out in accordance with APHA standards [7].A Shimadzu UV 2100 Spectrophotometer was used to measure the samples prepared using spectrophotometric techniques.

Data analysis
The following equations were used to determine removal efficiency (RE) and mass removal rate (MRR] [8]. Where  and  are the influents and the effluent concentrations, respectively (mg/L),  is the area of constructed wetland bed (m 2 ),  is the flow rate (m 3 /d), and MRR (g.m 2 /d).

The characteristics of textile wastewater
Textile wastewater contains high sulfate (> 200 mg/L) as well as sulfides (2.5 mg/L).Wastewater is black and yellow in color and is alkaline (pH > 8).The dye content is up to 268.56 units of Pt-Co.COD, TSS, TN, and TP concentrations were 543.33 mg/L, 232 mg/L, 2.82 mg/L, and 2.98 mg/L, while the ammonia concentrations, nitrate, and phosphate were 1.99, 0.27, and 0.26 mg/L.Seen black precipitate indicates metal sulfide deposits, where the results of metal measurements in wastewater for Cr, Pb, Cu, and Cd were 10.24 ug/L, 70.56 ug/L, 134.43 ug/L, 3, 43 ug/L, respectively.The content of COD, TDS, sulfates, sulfides, chlorides, and even heavy metals is usually very high.The content of textile waste used in this study is several parameters much lower than the characteristics of textile waste tested in previous studies [9,10,11].The maximum concentration to be processed in ecotechnology is in the range of 20% -50% dilution.

Removal efficiency (RE) of pollutants
The performance of CTW and adsorbent systems in reducing pollutants in textile wastewater can be seen in Table 1.At a concentration of textile wastewater with a dilution of 20%, the CTW system can increase the dissolved oxygen content to the range of 4 -7, the pH tends to be normal -alkaline (7.3 -8.2), reducing COD up to < 60%.CTW with Vetiveria zizanioides reduced TN and nitrate content by >66% and <50%, while the system with Heliconia psittacorum reduced >80% and <25%, respectively.CTW showed excellent performance in reducing ammonia up to > 90%.At this 20% dilution concentration, the dye content is not too concentrated and the CTW system is able to reduce it up to < 35%.
The decline in CTW performance was seen in the textile wastewater concentration test with a dilution of 50%.The decline in CTW performance was seen in the textile wastewater concentration with a dilution of 50%.The dissolved oxygen content increased to 5.5 mg/L and the pH of the effluent ranged from 6.8 to 8.8.The reduction in the concentration of TN and nitrate was still quite good, ranging IOP Publishing doi:10.1088/1755-1315/1260/1/0120486 adsorbent is better at removing ammonium compounds in textile waste than zeolite, with an efficiency of 67.163% for natural zeolite.Based on the EDX analysis bentonite has a fairly high oxygen content ranging from 70 -80% [12,13] and has the potential to oxidize ammonium compounds to nitrate.Bentonite adsorbent showed good performance in reducing dyes up to 64.84%.
In its application to the constructed treatment wetlands system, the adsorbent can be combined in a hybrid way to increase the efficiency of ammonium removal, and the content of nitrogen, silica, alumina, potassium, sodium, and magnesium [12,14,15] can enrich the nutrients for plants in the wetland system without the need to add compost considering that the textile industry wastewater contains sufficient nutrients to support plant growth.

CTW and adsorbent hybrid system recommendations
In the hybrid model of CTW and adsorbent in treating textile waste, the adsorbent's ability can increase dissolved oxygen levels, reduce dyes, and play a role in filtration by using pores capable of adsorption by using silica and alumina content on the adsorbent.The adsorbent's useful life is relatively shorter than other media in the CTWs system, so it needs to be separated into a separate compartment to make it easier to access its replacement (Figure 4).The CTWs system has a long lifetime in the adsorption of pollutants through plants and the media used and the removal of the dye with the help of microorganisms.In the adsorption process with bentonite, ammonia will be converted into nitrate through the nitrification process.The process of decomposition of ammonia compounds occurs in the aerobic zone.The high oxygen content in bentonite is very good for the oxidation process of ammonia to nitrate.In the CTW system, there is a process of deposition and filtration which is a physical process on the substrate media, as well as using adsorbents.The measurement of the dye content was carried out by filtering the textile wastewater.The efficiency of dye reduction using the CTW system is up to 70% in the Vetiveria zizanioides and 55% in the system with Heliconia psittacorum, with an average decrease of 49.53% and 35.51%.Efficiency Removal of dye using bentonite adsorbent shows a better decrease in dye content up to 64.84% using natural bentonite compared to zeolite which can only reduce dye content by < 10%.The combination of the CTWs system using an adsorbent as a pre-treatment before entering the cell of CTWs can improve the performance of CTWs by reducing the dye content up to 90%.
In the storage tank of textile wastewater, there is a process of binding sulfate concentration with heavy metals, and under alkaline pH conditions heavy metals are deposited, and through the sedimentation process, it can reduce the TSS concentration.In the adsorbent pond, there is an increase in dissolved oxygen content in the range of 5 -9 mg/L, reduced dyes < 65%, supply nutrients to plants CTWs reduced ammonia content > 90%, changes ammonia to nitrate, and filtration process of suspended solids.In the CTWs pood, there is a process of reducing the remaining dye content, reducing the concentration of COD, ammonia, nitrate, phosphate, total phosphorus, and total nitrogen, converting sulfides to sulfate, and TSS filtration.At the end of the system, it is equipped with an ecotoxicology pond to test the safety of the system before the treated water enters the water body.

Conclusion
The results showed that both ecotechnology, CTW, and adsorbents, were effective in reducing the pollutant in textile wastewater, including synthetic dyes, COD, ammonia, and other pollutants in a separate system.The two systems, CTW and adsorbent, can be combined in a single hybrid system to improve performance.The high oxygen content in the adsorbent can increase the dissolved oxygen content and reduce the ammonia concentration and the high adsorption of dyes can be used as a treatment system before entering the CTW system.Bentonite has sufficient nutrient content to supply the nutrient needs of the CTW system so additional compost is no longer needed as an initial starter for plant growth.
Credit authorship contribution statement E Susanti, H Wibowo, C Henny, D Rohaningsih, and E Prihatinningtyas as the main authors of the study.E Susanti contributed to the acquisition of funding, as well as the writing, reviewing, and editing.The main authors contributed to the conceptualization approach, methodology, investigation, and formal analysis.Moreover, H Fakhrurroja contributed to online monitoring systems, while BT Sudiyono was in charge of the facility construction.At last, D Febrianti, F Zulti, R Kurniawan, A Waluyo, and FS Lestari were doing the laboratory analysis.All authors contributed to oversight and provided feedback input on the work, and they all read and approved the final paper.

Figure 3 .
Figure 3. Adsorbent system configuration using zeolite (A and C) and bentonite (B and D).

Figure 4 .
Figure 4.The recommended hybrid system of CTW and adsorbents.