Industrial Water Treatment Research Articles

Performance of Recovered Coagulant from Water Treatment Sludge by Acidification Process

Aluminium sulphate (Al₂SO₄)³ or commonly known as alum has been used as a coagulation-flocculation agent by water treatment industries around the world, including Malaysia. Regardless of its effectiveness in purifying the raw water, it produces a large volume of alum sludge. In Malaysia, alum sludge is categorized as scheduled waste where it requires to be transported only to approved landfills and the costs could be high. Hence, reusing and recycling the alum sludge may be beneficial for water treatment industries in reducing the disposal cost. In this study, acidification method using nitric acid at a molarity of 0.5M – 2.0M is employed to recover a maximum percentage of aluminium from alum sludge. The findings showed that the difference in molarity of nitric acid is proportional to the recovery rate of aluminium up to 99% of the recovery. The performance of recovered coagulant in removing turbidity from raw water was evaluated at variations of dosage (0.5 – 12 mg/l) and pH (2 – 13). At an optimum dosage of 2 mg/l, the recovered coagulant efficiently removes the turbidity of raw water at 93.32% and achieved 99.47% at pH 7. Consequently, the use of recovered coagulant can promote a sustainable environmental approach to converting waterworks residuals into usable resources, particularly in water/wastewater treatment industries.

Coupling electrocoagulation with electro-oxidation for COD and phosphorus removal from industrial container wash water

• A process was developed for treatment of industrial container wash water (IWW). • Electrocoagulation (EC) and electrooxidation (EO) processes were successively used. • Optimum operating parameters of individual and coupled EC and EO were compared. • EC-EO combination allowed the removal of 97% of phosphorus and 95% of COD. • EC-EO combination reduced the treatment cost around 3.3 times than individual EO. Electrochemical processes such as electrocoagulation (EC) and electrooxidation (EO) have proved their effectiveness for the treatment of industrial refractory wastewater. This study aimed to strategically combine EC and EO processes for the treatment of highly contaminated wastewater (COD of 10,360 ± 665 mg/L and phosphorus concentration of 22.9 ± 0.9 mg/L) coming from industrial container wash water (IWW). In this regard, the EO and EC processes were investigated individually and then in combination. For the EO process, different operating parameters were investigated such as the type of anode, current density, type of electrolyte, amount of electrolyte, treatment time, and contamination concentration, while for the EC the current density and pH were studied. Although EO process decreased up to 91 ± 4.9% of COD, this process did not allow to reach the guideline (800 mg/L of COD) required for effluent discharge in the sewage urban networks. This was mainly attributed to the presence of phosphate ions which are known as hydroxyl radical scavengers. EC process was then firstly used as pre-treatment to remove phosphate ions from IWW, followed by EO process. The EC-EO combination allowed 97% and 95% of phosphorus and COD removal to meet the sewer discharge standard, respectively. A cost analysis showed that the EC-EO coupling reduced the operating costs to 7.3 CAD $/m 3 compared to 24 CAD$/m 3 recorded while EO process was used alone for the treatment of IWW.

Improving the efficiency and environmental reliability of water supply facilities using modern reagents

This article considers methods of selection of modern reagents for treatment of industrial waste water. Based on these articles, it is proposed to replace the inefficient flocculant used in the mechanical treatment plants of one of the oil refineries with a more modern reagent. Thus, increase the efficiency and reliability of treatment facilities.

Advanced oxidation of Trihalomethane (THMs) precursors and season-wise multi-pathway human carcinogenic risk assessment in Indian drinking water supplies

Advanced oxidation processes (AOPs) in water treatment industries can simultaneously offer disinfection and eradicate organic contaminants. The present work examined the direct exposure impact of various oxidative (UV, O3, and H2O2) and their eclectic combinations (UV/O3, H2O2/O3, and UV/H2O2) for the abolition of Trihalomethane (THMs) precursors. The application of the Fenton process proved to be the most effective technique for reducing TOC (85.23%) and UV254 (91.11%) than other used AOPs. Higher removal of THMs precursors found in the Fenton process may be attributed to the higher degradation potential of hydroxyl radical generated from this process than other AOPs. The deformed ferrous iron salts (Fe2+) in the Fenton reagent catalyzed the hydrogen peroxide (H2O2) and produced highly reactive radicals. Seasonal probabilistic lifetime cancer and non-cancer risks of THMs in males and females were also investigated in the drinking water supplies of five major cities in India. Comparative risk analysis through different pathways revealed significant risk from oral ingestion (99%), followed by inhalation exposure (0.77%) and dermal absorption (0.002%), where females were found at higher risk of cancer. Sensitivity analysis using a radar plot was also performed to identify the most influential parameter affecting the total risk of cancer. The Risk value of chloroform (CF) was highest among the THMs compound in all the WTPs for both seasons. Seasonal risk assessment revealed a higher risk of cancer in the pre-monsoon season.

Removal of Lead from Metal Conaminated Industrial Waste Water By Adsorption onto Banana Peel

Banana peel, a fruit waste was used to produce biosorbant through environment friendly process. Banana peels were washed, dried and ground, before being used for treatment of industrial waste water and used for lead removal. The experiments were carried out by different concentration of dosage for incubation time 24 hours in the batch mode for the measurement of adsorption capabilities. The powdered as an adsorbent, in orbital shaker at 150 to 180 rpm at 25˚C. 8ml waste water sample was used in triplet, each was kept with 10mg, 20mg, and 30mg concentration of banana peel and obtained equilibrium adsorption capacity was 0.649, 0.184, 0.021mg/L respectively. The separation of bio adsorbent and solution was carried out by filtration with Whatman Filter Paper No.42 and the filtrate stored in sample cans for determine the metal lead ion concentration using Atomic Absorption Spectrophotometer (AAS). Heavy metal ions were estimated before and after addition of powdered adsorbents. The powder of that bio sorbent was used for treatment of waste water with different proportion of adsorbents, variation of pH and contact time. Lead adsorption onto banana peel was depended upon the controlling parameter such as pH, conductivity, Total Dissolved solids, Salinity, Sodium, Potassium by Flame Photometer and Lead ion concentration by Atomic Absorption Spectrophotometer (AAS). Slightly basic water (pH = 8.3) was found to be suitable for lead removal. Equilibrium data were well fitted (R2 = 0.998) with the Langmuir and Freundlich isotherms. The monolayer adsorption capacity was 0.025 mg/L on 30 mg banana peel. The calculated RL and ‘n’ values has proved the favorability of lead adsorption onto banana peel. Lead adsorption was followed the second order kinetic properly rather than other models. Solvent 0.1N Sulphuric acid showed higher desorption of lead (60%) and adsorption-desorption process can be continued till seven cycles efficiently. Keywords: Banana peel, Bio sorbents, heavy metal, lead, atomic absorption spectrophotometer

L-lysine functionalized Ti3C2Tx coated polyurethane sponge for high-throughput oil–water separation

Creating an efficient method that can provide simple, practical and high-throughput separation of oil–water mixtures has proved extremely challenging. Two-dimensional layered Ti3C2Tx MXene material with excellent hydrophilicity has attracted substantial attention for oil–water separation. However, conventional Ti3C2Tx separation membranes are susceptible to contamination by oil due to its relatively high adhesion to oil, hindering its practical applications in high-efficiency oil–water separation. To make Ti3C2Tx have underwater superoleophobicity and low oil adhesion, the surface of Ti3C2Tx can be modified by introducing hydrophilic groups. Herein, L-lysine functionalized Ti3C2Tx (Ti3C2Tx-Ly) was firstly prepared by decorating L-lysine on Ti3C2Tx through electrostatic interaction and hydrogen bonding. A facile dip-coating method is then used to coat polyurethane (PU) sponge with Ti3C2Tx-Ly, obtaining a superhydrophilic/underwater superoleophobic Ti3C2Tx-Ly @PU sponge. Owing to the excellent underwater superoleophobicity resulting from hydrophilic groups (–OH、–NH3) on the surface of Ti3C2Tx-Ly nanosheets and the enlarged interlayer spacing of Ti3C2Tx, the Ti3C2Tx-Ly @PU sponges demonstrated outstanding separation performance for a series of oil–water mixtures. Specifically, the Ti3C2Tx-Ly @PU sponge exhibits low oil adhesion and superhydrophilic (WCA = 0°)/submerged superoleophobic (UOCA > 155°) properties. The Ti3C2Tx-Ly @PU sponges displayed the best separation performance for cyclohexane/water mixture, and the maximum permeation flux is up to 221892 L m–2 h–1, accompanied by a remarkable separation efficiency of higher than 99.2% after 100 cycles. The permeation flux has exceeded most of the previous reported multifunctional separation membranes. In addition, the Ti3C2Tx-Ly @PU sponge also showed excellent separation performance for high-density oil dichloromethane/water with a separation efficiency over 99.4%. Of note, the Ti3C2Tx-Ly @PU sponge features excellent chemical stability to corrosive media, such as acidic, alkaline, and high salt solutions, possessing great potential for real-world applications. Furthermore, the as-prepared Ti3C2Tx-Ly @PU sponge exhibits rapid and efficient separation of oil-water mixtures through a fully gravity-driven process, which makes it a good candidate for industrial oil-contaminated water treatment and oil spill clean-up, and also provides new insights into the design and development of functional Ti3C2Tx through L-lysine modification. Therefore, this work reports a facile and promising way to fabricate scalable superhydrophilic/underwater superoleophobic sponge material for highly efficient oil–water separation.

Intensity and regimes changing of hydrodynamic cavitation considering temperature effects

Venturi-type cavitation reactors still appear as the most promising candidates for industrial-scale production due to their cheapness and ease of construction, scaling, and replicability. The effects of temperature on hydrodynamic cavitating flows in a Venturi section are investigated to find the optimum reacting conditions enhancing cavitating treatment intensity. The flow conditions are varied with 4 different flow rates and a wide range of temperatures between 28 ℃ to 63 ℃. Results show that both the cavitation length and the transition between sheet and cloud cavitation regimes are influenced by a combination of the pressure drop (indicated by the cavitation number σ), the inertial/viscous effects (controlled by the Reynolds number Re), and the thermal effect (indicated by the thermodynamic parameter Σ). As the temperature is elevated, both the cavitation length and thickness increase first, and then decrease. The cavitation intensity peaks at a transition temperature of 58 ℃. With the increase of cavitation length and thickness, the regimes tend to switch earlier from the attached sheet cavity to periodical cloud shedding, and the shedding frequency decreases accordingly. When the temperature is progressively increased, the changing of cavitating flow structures is illustrated through Proper Order Decomposition analysis. This study allows us to understand the instability, size evolution, shedding regime transition of partial cavities considering thermodynamic effects. Recommendations are provided to beer-brewing, biodiesel production, or water treatment industries that working under a 55 ℃ to 60 ℃ temperature range will attain the highest cavitation intensity.

Efficiency Analysis of Industrial Water Treatment in China Based on Two-stage Undesirable Fixed-sum Output DEA Model

Abstract China is a country with the most water consumption, so it is lack of water resources. Industry has brought serious water pollution while driving economic development, which leads to the destruction of ecological environment. With the improvement of environmental awareness, many scholars have shifted their research direction to how to improve the ecological environment. Most studies consider the whole system as a “black box”, regardless of its internal structure. Therefore, a method to identify inefficiency is necessary and some suggestions for optimization are given. In this paper, a two-stage undesirable fixed-sum output data envelopment analysis (DEA) model is proposed. The industrial chemical oxygen demand (COD) emission during 2011–2015 are adjusted, and the efficiency values are calculated by heuristic search algorithm. The efficiency of 30 provinces and cities is divided into eastern, central and western regions. The model can identify the inefficient stage in industrial system, and find the source of low efficiency in the system. The analysis shows that the efficiency of eastern region is the highest, while the overall efficiency is inclined to the pollutant treatment stage. Finally, the paper puts forward some suggestions for the low efficiency areas, which can save water while ensuring economic benefits, and provide new direction for water pollution reduction and improve the ecological environment.

Biosorption of heavy metals: Transferability between batch and column studies

The design of an industrial water treatment system using sorption is based on laboratory column tests. To verify the applicability of a column sorption system at industrial scale, it is necessary to determine the system's breakthrough time (BT) in a laboratory setting. In a laboratory column set-up, BT is referred to as the time taken by the adsorbate to appear at column outlet for the first time. This is when the mass transfer zone (MTZ), where the equilibrium sorption occurs, reaches the end of the sorbent bed. However, such laboratory set-up requires significant resources including laboratory space, time and multiple trials, which is the opposite to the batch experimental approach that is commonly used to assess efficiency of sorbents. This study identified batch sorption parameters that can be used to determine BT for a column sorption setting for three toxic heavy metals commonly found in industrial wastewater, namely, Pb2+, Cd2+ and Cu2+. The study conducted a comprehensive evaluation of the relationships between column BT and its key influential factors, namely, equilibrium sorption capacity (qe), pseudo second-order kinetic rate constant (k2) and initial sorption rate (h). The results revealed that BT can be better estimated using h compared to qe and k2. As such, a batch experiment which is more resource efficient could be undertaken for an initial estimation of the experimental BT of a column system. Moreover, a simulation model developed to replicate column sorption could demonstrate the behaviour of the breakthrough curve, which is a key to the selection and assessment of the performance of a sorbent in an adsorbent column. The estimation errors in qe and k2 were found to influence the simulation outcomes. Hence, it is necessary to further investigate the other factors that can potentially influence sorption behaviour.

Green synthesized CuI as an adsorbent and a photocatalyst in the removal of aqueous reactive red 256 & reactive black 5 dyes

The extensive utilization of dyes in the industries and the consequent generation of their effluents in the water bodies have posed a major risk to the environment and mankind. Therefore, there is an increased necessity for waste water treatment in textile industries. The present study involves the utilization of highly versatile copper (I) iodide synthesized using Hibiscus rosa-sinensis L. flower extract (CuI-FE) in the removal of textile dyes. The synthesized material was characterized using XRD and found to be highly crystalline with an average crystallite size of 89.01 nm. The average particle size of the agglomerated CuI-FE was measured to be 492.7 nm using HR-SEM. The d-spacing calculated from HR-TEM was found to match with that from XRD. XPS analysis confirmed the oxidation state of Cu(+1) in CuI-FE. The purity of the syntheised CuI-FE was ascertained from its EDAX data. It was further characterized using BET, FTIR and UV-Visible spectroscopic techniques. Batch adsorption studies of Reactive Red 256 (RR) and Reactive Black 5 (RBL) were probed in the presence of CuI-FE and the respective adsorption capacity of RR and RBL were found to be 135.22 and 176.42 mg/g. LCMS data taken of the solution after Batch adsorption studies at the end of 24 h showed the presence of intermediates of low molecular weight that are environmentally benign confirming that the initial adsorption process was followed by degradation of dyes. A possible dye degradation pathway was proposed using LCMS data analysis.

Approach for assessing environmental handprints

The need to reveal positive environmental consequences of offerings has risen as urgent climate actions are needed from companies. The environmental handprint approach was developed to indicate the positive environmental impacts of a solution offered to a client. The environmental handprint approach builds upon the previously published carbon handprint approach. The approach follows the guidelines of ISO standards on Life Cycle Assessment (LCA) but complements them with instructions for calculating positive environmental impacts. The environmental handprint framework allows consideration of several different environmental impacts including climate impacts, air quality, and utilization of nutrients, water and resources, and it can be applied to products, services, organisations and projects. The framework consists of four main stages: 1. Handprint requirements, 2. Additional LCA requirements, 3. Quantification, 4. Communication. The handprint approach provides an important addition to life cycle studies. Handprints can be used by organizations to communicate the environmental benefits of their products, services, and technologies. They also serve as an aid to identify improvement potential throughout the life cycle of an offering, thus supporting product development and decision making. Case studies supported the methodology development. A case related to water handprint in water treatment in the mining industry is presented in this paper.

Efficiency of using the Kazakhstan zeolites for the purification of water from iron ions

The problem of provision of the population with high-quality drinking water is currently one of the most topical in connection with the unsatisfactory technical condition of the existing water supply systems and pollution of the water sources. Natural zeolites, which have a sufficiently high sorption capacity, cation-exchange properties, relatively low cost and availability, are increasingly being used in recent times for water purification. The mineralogical properties of natural zeolites of the Tayzhuzgen and Shankanai deposits have been investigated. A comparative study of the sorption properties of the natural and modified zeolites of the Kazakhstan deposits has been carried out on model solutions, containing iron ions (Fe2+). The exchange mechanism and the degree of extraction of ions from the solutions have been established. The efficiency of the municipal water purification in the Auezovskiy district of Almaty with zeolites of the Shankanai field has been equal to 85.94%. This suggests a possibility of using these zeolites to purify water from iron ions with the purpose of water treatment in the dairy industry.

Membrane assisted crystallization of active pharmaceutical ingredients (APIs) by forward osmosis and its effect on crystal size and morphology

At present and in the past decade, forward osmosis (FO) membrane technology has grown as an emerging technology in various area specially desalination, waste and drinkable water treatment, pharmaceutical, and food processing industry. FO depends on the osmotic pressure difference generated between feed solution (FS) and that of draw solution (DS) which results the separation of selective liquid components possible. FO is energy intensive process creating concentration gradient between FS and DS, which is driving force for separation and concentration of saturated solutions. Membrane assisted crystallization (MAC) process; a combination of membrane technology with conventional crystallization processes is useful hybrid crystallization process recently developing mostly in pharmaceutical and food processing sectors. In this work, comprehensive study has been done on the membrane assisted FO process which utilizes various operation conditions which are necessities for development of hybrid MAC for the active pharmaceutical ingredients (APIs). Recently developed membranes have intrinsic characteristics of operational simplicity, high permeability, selectivity and efficiency. These characteristics make possible to develop a technology which satisfies the concept of various APIs production. The main objective of this present study is to compare the effect of various process parameters such as drug solution supersaturation, crystallization temperature, and time on crystal size and morphology of APIs by conventional crystallization and MAC.

Effectiveness of natural coagulants in water and wastewater treatment

Natural waterways are contaminated due to industrialization, urbanization, population growth etc., degrading their quality. Contaminated waterways cause numerous health and environmental hazards. Therefore, it is imperative to remove contaminants. Coagulation is one of the efficient primary chemical treatment methods that could be used to treat such contaminants. Natural coagulants have gained popularity in the water and wastewater treatment industry due to their advantage over chemical coagulants. Natural coagulants are derived from either plants, animals, or microorganisms. This study has elaborated on the nature and mechanisms, and types of natural coagulants. In this review work, many studies have proposed several types of natural coagulants. However, plant-based natural coagulants extracted from different plant components have been extensively discussed and compared based on their application and efficiency in water and waste treatment. The primary purpose of this review is to refine the knowledge on the potential use and optimization of the effectiveness of eco-friendly and sustainable natural coagulants. Besides, the development efforts and the barriers reported by recent findings for the commercialization of natural coagulants are also discussed. Further, few modified natural coagulants have also been presented for exploring the other possible approaches to promote their usage in water and wastewater treatment in the future studies.

The construction and application of physiologically based toxicokinetic models for acrylamide, glycidamide and their biomarkers in rats and humans

Acrylamide (AA), a class 2A probable carcinogen to humans classified by the International Agency for Research on Cancer, has attracted extensive attention worldwide since it was widely used in industrial and domestic water treatment and detected in thermal processing foods. The metabolic adducts of AA and its primary metabolite glycidamide (GA) have been served as biomonitoring markers of AA intake, but the physiologically based toxicokinetics (PBTK) models to estimate internal dosimetry still remain unclear. An updated PBTK model for AA, GA and their metabolic biomarkers in rats and humans was developed and extended with time-course datasets from both literatures and our experiments. With adjustments to the model parameters, linear regression correlation coefficient (R2) between the fitting values and the validation datasets of rats and humans was greater than 0.76. The current model fits well with the experimental datasets of urinary N-acetyl-S-(2-carbamoylethyl)-l-cysteine (AAMA) and (N-(R,S)-acetyl-S-(carbamoyl-2-hydroxyethyl)-l-cysteine) (GAMA) of rats exposed to AA from 0.1 to 50 mg/kg b.w. and humans exposed to AA from 0.0005 to 0.020 mg/kg b.w., indicating the robustness of the current models. Parameters for adduct of AA with N-terminal valine of hemoglobin (AAVal) were extended to humans and validated. Kinetic parameters for rats were assessed and validated based upon fit to the experimental datasets for liver N3-(2-carbamoyl-2-hydroxyethyl)-adenine (N3-GA-Ade) and N7-(2-carbamoyl-2-hydroxyethyl)-guanine (N7-GA-Gua) adducts. Compared with the previous model, the developed model included the correlation between AA intake and its mercapturic acid adducts, AAMA and GAMA, in a larger dose range with new experimental data, and parameters for AAVal, N3-GA-Ade and N7-GA-Gua were improved and verified. The current multi-component PBTK models provide a superior foundation for the estimation of short-term to medium and long-term intake levels of human exposure to AA.

A Protocol for Electrocatalyst Stability Evaluation: H2O2 Electrosynthesis for Industrial Wastewater Treatment.

Electrocatalysis has been proposed as a versatile technology for wastewater treatment and reuse. While enormous attention has been centered on material synthesis and design, the practicality of such catalyst materials remains clouded by a lack of both stability assessment protocols and understanding of deactivation mechanisms. In this study, we develop a protocol to identify the wastewater constituents most detrimental to electrocatalyst performance in a timely manner and elucidate the underlying phenomena behind these losses. Synthesized catalysts are electrochemically investigated in various electrolytes based on real industrial effluent characteristics and methodically subjected to a sequence of chronopotentiometric stability tests, in which each stage presents harsher operating conditions. To showcase, oxidized carbon black is chosen as a model catalyst for the electrosynthesis of H2O2, a precursor for advanced oxidation processes. Results illustrate severe losses in catalyst activity and/or selectivity upon the introduction of metal pollutants, namely magnesium and zinc. The insights garnered from this protocol serve to translate lab-scale electrocatalyst developments into practical technologies for industrial water treatment purposes.

Acoustically excited microstructure for on-demand fouling mitigation in a microfluidic membrane filtration device

Membrane separation is widely used in food, pharmaceutical and water treatment industries but suffers a longstanding challenge of fouling. In this article, acoustically excited microstructures are demonstrated as a new mechanism to mitigate membrane fouling and remove cake layer aggregations formed on a microfluidic membrane-on-chip device. With acoustic streaming induced by oscillating microstructures near the membrane surface, cake layer fouling was effectively broken up and removed on the acoustofluidic membrane separation device within 100 milliseconds. The device is simple to fabricate and offers direct observation of crossflow microfiltration across the device membrane, giving valuable insight to particle fouling events often unobtainable in traditional membrane device configurations. The device bolsters advantages like label-free and reagent-free particle separation and in situ membrane cleaning during separation, providing a new mechanism for membrane separation applications used across industry.

Bamboo residue as a potential activated carbon for removal of water pollutants: a commentary

ABSTRACT Bamboo is one of the fastest-growing plants that exist on earth and can be found in many countries. Its application generally ranges across both the engineering and non-engineering sectors. Traditionally, bamboo is mainly used in the construction field, but recent trends and studies have also shown its potential in the water treatment industry as a low-cost adsorbent. Thus, this paper aims to highlight the recent studies on bamboo residue as a potential precursor for activated carbon as well as its performance in treating water pollutants. Apart from that, the current limitations, and suggestions on the further development of bamboo activated carbon, are also integrated to provide insight on its potential usage in the industrial process.

Application of wheat bran based biomaterials and nano-catalyst in textile wastewater

The exponential expansion of industrial production during the past few decades has been detrimental to the environment owing to increased contamination with chemical pollutants such as heavy metals and dyes. Each year, large volumes of agricultural byproducts are generated as waste materials from various food crops, one which is wheat bran from wheat, the world’s largest food crop. Approximately 12% of dyes made from synthetic materials used by the textile industry are lost in the production and processing phases; similarly, 20% of the resulting dye reaches the ecosystem via industrial wastewater effluents. These dyes are highly radioactive and have potentially negative consequences; therefore, several federal and environmental authorities have enacted stringent regulations and restrictions prohibiting the dumping of dye-containing raw sewage into existing water bodies. Although there are several methods to remove dye from wastewater, the preferred approach is adsorption. Activated charcoal is one of the best adsorbents. However, its use in industrial water treatment, mainly in developing nations, is confined because of its high cost. Owing to the increasing price of activated carbon, researchers have been tasked with developing a low-cost, reliable adsorbent that can be substituted for activated carbon. Several adsorbents, such as biosorbents, carbon-based nano-adsorbents, transition metal-based oxides, Metal-organic frameworks MOFs, and polymer-based adsorbents, are used to treat dye-containing wastewater. This chapter compiles the results of various studies that analyzed the use ofwheat bran as an absorbent for eliminating dyes and other toxic effluents from the textile industry. Dye removal via adsorption and nano-materials is expected to be a promising method for the treatment of dye-laden water.

Industrial water treatment within a wetland planted with Hemarthria compressa and subsequent effluent reuse to grow Abelmoschus esculentus

This study assesses the potential of constructed wetland systems to treat tannery effluent (TE) and mixed industry effluent (MIE). After each of the three influent cells acting as settling cells, three treatment cells in horizontal series along with a Control were applied. Each of the cells was subjected to horizontal surface flow and planted with Hemarthria compressa (L.f.) R.Br. (perennial whip grass). The percent decline in heavy metal concentrations between settling and Cell 3 over a period of 60 days varied as follows: zinc (Zn; 35.83–95.59), chromium (Cr; 30.63–95.49), copper (Cu; 24.3–97.05) and nickel (Ni; 20.3–93.2). The drop in chemical oxygen demand (COD mg L−1) ranged between 3.95 and 72.14%, whilst the total dissolved solids (TDS g L−1) decline was between 3.23 and 98.75%. The pH and electrical conductivity (EC) drop ranges were between 1.4 and 11.72% along with up to 92.92%, respectively. The determined decline rates of pollutants and the cumulative biomass yield of H. compressa at p = 0.05 were between 0.76 and 0.96 (20 d−1). The heavy metal tolerance index for H. compressa in TE and MIE were 0.25–3.25 and 0.25–2.2, respectively. Although treated TE and MIE discharged from Cell 3 of each of the effluent treatment series on the 60th day had Zn, Ni, Cr and Cu concentrations greater than the local permissible limits (Punjab Environmental Quality Standards) of Liquid Industrial Effluents. The treated water through the constructed wetland system proved safe for cultivation of okra (Abelmoscus esculentus (L.) Moench) vegetables.