Biosorption of chromium by live and dead cells of Bacillus nitratireducens isolated from textile effluent.

Bacillus nitratireducens was isolated from textile effluent and showed high tolerance to chromium (Cr), reaching up to a 1000 mg/L MIC value. This research was aimed at utilizing biosorbents from live and dead cells of B. nitratireducens to remove Cr from an aqueous solution. A batch biosorption test was performed, and mechanisms analysis was approached by an adsorption-desorption test, SEM-EDS, and FTIR analysis. Cr removal by dead cells in 25, 50, and 100 mg/L of Cr were 58.99 ± 0.7%, 69.8 ± 0.2%, and 82.87 ± 0.11%, respectively, while that by live cells was 73.08 ± 1.9%, 80.27 ± 6.33%, and 86.17 ± 1.93%, respectively. Live cells showed significantly higher Cr removal and adsorption capacities as compared to dead cells. In all concentrations, absorption contributed more than adsorption to the Cr removal by both live and dead cells. Absorption of Cr was subjected to occur due to passive mechanisms in dead cells while involving some active mechanisms in live cells. SEM-EDS confirmed the detection of Cr on the cell surface, while FTIR revealed the shifting of some peaks after the biosorption test, suggesting interactions between Cr and functional groups. Further TEM analysis is suggested to be conducted as a future approach to reveal the inner structure of cells and confirm the involvement of absorption mechanisms.

Effect of the number of Cyperus rotundus and medium height on the performance of batch-constructed wetland in treating aquaculture effluent.

Increasing aquaculture cultivation produces large quantities of wastewater. If not handled properly, it can have negative impacts on the environment. Constructed wetlands (CWs) are one of the phytoremediation methods that can be applied to treat aquaculture effluent. This research was aimed at determining the performance of Cyperus rotundus in removing COD, BOD, TSS, turbidity, ammonia, nitrate, nitrite, and phosphate from the batch CW system. Treatment was carried out for 30 days with variations in the number of plants (10, 15, and 20) and variations in media height (10, 12, and 14 cm). The result showed that aquaculture effluent contains high levels of organic compounds and nutrients, and C. rotundus can grow and thrive in 100% of aquaculture effluent. Besides that, the use of C. rotundus in CWs with the effect of numbers of plants and media height showed performance of COD, BOD, TSS, turbidity, ammonia, nitrate, nitrite, and phosphate with 70, 79, 90, 96, 64, 82, 92, and 48% of removal efficacy, respectively. There was no negative impact observed on C. rotundus growth after exposure to aquaculture effluent, as indicated by the increase in wet weight, dry weight, and growth rate when compared to the control. Thus, adding aquaculture effluent to CWs planted with C. rotundus supports the growth and development of plants while also performing phytoremediation.

Integrating phytoremediation and mycoremediation with biosurfactant-producing fungi for hydrocarbon removal and the potential production of secondary resources.

Treatment of petroleum-contaminated soil to a less toxic medium via physical and chemical treatment is too costly and requires posttreatment. This review focuses on the employment of phytoremediation and mycoremediation technologies in cleaning hydrocarbon-contaminated soil which is currently rare. It is considered environmentally beneficial and possibly cost-effective as it implements the synergistic interaction between plants and biosurfactant producing mycorrhiza to degrade hydrocarbon contaminants. This review also covers possible sources of hydrocarbon pollution in water and soil, toxicity effects, and current technologies for hydrocarbon removal and degradation. In addition to these problems, this review also discusses the challenges and opportunities of transforming the resultant treated sludge and treating plants into potential by-products for a higher quality of life for future generations.

Performance of a modified and intermittently operated slow sand filter with two different mediums in removing turbidity, ammonia, and phosphate with varying acclimatization periods.

The present study investigated the utilization of blood clam shells as a potential substitute for conventional media, as well as the influence of the acclimation time on the efficacy of an intermittent slow sand filter (ISSF) in the treatment of real domestic wastewater. ISSF was operated with 16 h on and 8 h off, focusing on the parameters of turbidity, ammonia, and phosphate. Two media combinations (only blood clam shells [CC] and sand + blood clam shells [SC]) were operated under two different acclimatization periods (14 and 28 d). Results showed that SC medium exhibited significantly higher removal of turbidity (p < 0.05) as compared to CC medium (45.99 ± 26.84 % vs. 3.79 ± 9.35 %), while CC exhibited slightly higher (p > 0.05) removal of ammonia (23.12 ± 20.2 % vs. 16.77 ± 16.8 %) and phosphate (18.03 ± 11.96 % vs 13.48 ± 12 %). Comparing the acclimatization periods, the 28 d of acclimatization period showed higher overall performances than the 14 d. Further optimizations need to be conducted to obtain an effluent value below the national permissible limit, since the ammonia and phosphate parameters are still slightly higher. SEM analysis confirmed the formation of biofilm on both mediums after 28 d of acclimatization; with further analysis of schmutzdecke formation need to be carried out to enrich the results.

Maximizing diesel removal from contaminated sand using Scirpus mucronatus and assessment of rhizobacteria addition effect.

Phytoremediation is one of the green technologies that is friendly to nature, utilizes fewer chemicals, and exhibits good performance. In this study, phytoremediation was used to treat diesel-contaminated sand using a local aquatic plant species, Scirpus mucronatus, by analyzing the amount of total petroleum hydrocarbons (TPHs). Optimization of diesel removal was performed according to Response Surface Methodology (RSM) using Box-Behnken Design (BBD) under pilot-scale conditions. The quadratic model showed the best fit to describe the obtained data. Actual vs. predicted values from BBD showed a total of 9.1 % error for the concentration of TPH in sand and 0 % error for the concentration of TPH in plants. Maximum TPH removal of 42.3 ± 2.1 % was obtained under optimized conditions at a diesel initial concentration of 50 mg/kg, an aeration rate of 0.48 L/min, and a retention time of 72 days. The addition of two species of rhizobacteria (Bacillus subtilis and Bacillus licheniformis) at optimum conditions increased the TPH removal to 51.9 ± 2.6 %. The obtained model and optimum condition can be adopted to treat diesel-contaminated sand within the same TPH range (50-3000 mg/kg) in sand.

A review of the treatment technologies for hexavalent chromium contaminated water.

The toxicity of hexavalent chromium (Cr(VI)) present in the environment has exceeded the current limits or standards and thus may lead to biotic and abiotic catastrophes. Accordingly, several treatments, including chemical, biological, and physical approaches, are being used to reduce Cr(VI) waste in the surrounding environment. This study compares the Cr(VI) treatment approaches from several areas of science and their competence in Cr(VI) removal. As an effective combination of physical and chemical approaches, the coagulation-flocculation technique removes more than 98% of Cr(VI) in less than 30 min. Most membrane filtering approaches can remove up to 90% of Cr(VI). Biological approaches that involve the use of plants, fungi, and bacteria also successfully eliminate Cr(VI) but are difficult to scale up. Each of these approaches has its benefits and drawbacks, and their applicability is determined by the research aims. These approaches are also sustainable and environmentally benign, thus limiting their effects on the ecosystem.

Enhanced leachate phytodetoxification test combined with plants and rhizobacteria bioaugmentation.

Plant combination and rhizobacterial bioaugmentation are the modification of constructed wetlands (CWs) to promote the detoxification of leachate. In this study, characterization of leachate was carried out to ensure the maximum concentration of leachate that did not affect the plant's growth. Herein, the identification of leachate-resistant rhizobacteria is used to determine the type of bacteria that is resistant and has the potential for leachate processing in the next step. The phytodetoxification test is carried out by comparing the addition of rhizobacteria and without the addition of rhizobacteria to detox leachate parameter Chemical Oxygen Demand (COD), Biological Oxygen Demand (BOD), Total Suspended Solid (TSS), Total Nitrogen (TN), Cadmium (Cd), and Mercury (Hg). Results showed that used plants could still live in the largest leachate concentration of 100%. The rhizobacteria that were identified and bioaugmented in the reactor were Bacillus cereus, Nitrosomonas communis, and Pseudomonas aeruginosa. Phytodetoxification test by a single plant showed the efficiency ranged between 40% and 70%. The addition of rhizobacterial bioaugmentation and plant combination can improve the percentage of COD 80.47%, BOD 84.05%, TSS 80.05%, TN 75.58%, Cd 99.96%, and Hg 90%. These modifications are very influential for leachate detoxification through plant uptake and rhizodegradation processes.

Metabolic pathway of Cr(VI) reduction by bacteria: A review.

Heavy metal wastes, particularly hexavalent chromium [Cr(VI)], are generated from anthropogenic activities, and their increasing abundance has been a research concern due to their toxicity, genotoxicity, carcinogenicity and mutagenicity. Exposure to these dangerous pollutants could lead to chronic infections and even mortality in humans and animals. Bioremediation using microorganisms, particularly bacteria, has gained considerable interest because it can remove contaminants naturally and is safe to the surrounding environment. Bacteria, such as Pseudomonas putida and Bacillus subtilis, can reduce the toxic Cr(VI) to the less toxic trivalent chromium Cr(III) through mechanisms including biotransformation, biosorption and bioaccumulation. These mechanisms are mostly linked to chromium reductase and nitroreductase enzymes, which are involved in the Cr(VI) reduction pathway. However, relevant data on the nitroreductase route remain insufficient. Thus, this work proposes an alternative metabolic pathway of nitroreductase, wherein nitrate activates the reaction and indirectly reduces toxic chromium. This nitroreductase pathway occurs concurrently with the chromium reduction pathway.

Plant-based coagulants/flocculants: characteristics, mechanisms, and possible utilization in treating aquaculture effluent and benefiting from the recovered nutrients.

The increasing intensification of the aquaculture industry requires the development of new strategies to reduce the negative impacts of wastewater on the environment. Plant-based coagulants/flocculants, regarded as one of the environmentally friendly technologies for wastewater treatment, show good performance in the removal of suspended solids from wastewater. The aforementioned technology involves the utilization of plants as coagulants/flocculants in the treatment process and produces nontoxic sludge as treatment by-products. The produced sludge could be converted into valuable compounds used in agriculture. This review summarizes coagulation-flocculation by using plant-based coagulants/flocculants, its mechanisms, operational factors that control the treatment process, and its application in the treatment of wastewater, especially aquaculture effluent. Moreover, this work discusses the potential utilization of aquaculture sludge as a valuable compound used in agriculture. The presented review aims to emphasize the potential of using plant-based coagulants/flocculants in the treatment of aquaculture effluent and explore the potential of using the produced sludge as fertilizer for plants to solve problems related to sludge handling and the toxicity of inorganic coagulants in a recirculating aquaculture system. This paper concluded that utilization of recovered nutrients in the form of solids is feasible for agricultural purposes, while a hydroponic system can be used to reclaim the nutrients in the form of solution.

Assessing the effect of multiple variables on the production of bioflocculant by Serratia marcescens: Flocculating activity, kinetics, toxicity, and flocculation mechanism.

Bioflocculants gain attention as alternatives to chemical flocculants because they are more environmentally friendly and highly biodegradable. This study aims to improve the bioflocculant production by Serratia marcescens using one-variable-at-a-time (OVAT) analysis and analyze its flocculating activity performance, toxicity, and the flocculation mechanism. The effect of multiple variables including initial inoculum size, pH, mixing speed, temperature, growth medium, and incubation period was assessed through OVAT. Flocculating activity was then determined via jar test analysis, and toxicity test was performed using Daphnia magna and Daphnia pulex. The flocculation mechanism was determined via particle size distribution and zeta potential analysis. The optimum conditions for the improved bioflocculant production were as follows: 10% v/v initial inoculum size, pH 7, mixing speed of 150 rpm, room temperature, nutrient broth medium, and 72 h of incubation period. Scanning electron microscopy showed flake-like intact structure with coarse surface. The produced bioflocculant showed flocculating activity of 48% in 5227 ± 580 NTU initial kaolin turbidity with 1 mg/L concentration and 5% v/v dosage of bioflocculant, following the second-order kinetics. Toxicity test to D. magna and D. pulex showed the 48 h LC50 values of 8.06 and 6.42 g/L, respectively; these values are greatly higher than the fabricated chemical flocculants. The flocculation process using bioflocculant produced by S. marcescens was suggested to occur via bridging mechanism because it greatly affected the particle size distribution. Results indicated that bioflocculant produced by S. marcescens is much environmentally friendly and has great potential for turbidity removal in water/wastewater.

A comprehensive review of domestic-open waste burning: recent trends, methodology comparison, and factors assessment.

Open burning is a waste management practice performed by many people worldwide, especially in developing countries. Lack of detailed data of open burning practices may lead to a misinterpretation during data analysis, especially when estimating global/local emissions and assessing risks. This study presents a comprehensive review of current research trends, methodological assessments, and factors behind open waste burning practices from published literature. This review used systematic methods such as PRISMA 2020 methodology, a bibliometric approach, and qualitative content analysis to determine and assess 84 articles related to open burning. The results show that environmental risks and emission factors related to open burning incidents at the landfill or residential level are preferable topics that will be rising in the years to come. Coupling methods such as a transect-based approach with a questionnaire survey and mobile-static plume sampling to determine the activities and incidents as baseline data for risk assessment will help researchers gain a robust dataset of open burning emission inventory. In addition, it was found that environmental knowledge and awareness levels influence open burning practices, thereby opening up opportunities for future research. Supplementary Information: The online version contains supplementary material available at 10.1007/s10163-022-01430-9.

Distribution of organochlorine pesticide pollution in water, sediment, mollusk, and fish at Saguling Dam, West Java, Indonesia.

This study aims to determine the distribution of organochlorine pesticide pollution in water, sediments, mollusks, and fish at Saguling Dam as baseline data of organochlorine pollution. Samples were obtained from 12 locations, with 9 and 3 sampling points inside and outside the dam, respectively. Measurement of organochlorine residues was carried out using methods of extraction, purification, evaporation, and gas chromatography. Results showed the presence of several types of organochlorine compounds, namely, lindane, aldrin, dieldrin, heptachlor, dichlorodiphenyltrichloroethane (DDT), and endosulfan. Aldrin was dominant in water (2-37 µg/L) and sediments (2-1438 µg/L), while DDT and heptachlor were dominant organochlorine compounds in mollusks (13-2758 µg/L) and fish (11-104 µg/L), respectively. Sediments demonstrated higher organochlorine concentrations than water, mollusk, and fish. The distribution of organochlorine was affected by land use around the Citarum watershed and pollutant input from tributaries.

Practical limitations of bioaugmentation in treating heavy metal contaminated soil and role of plant growth promoting bacteria in phytoremediation as a promising alternative approach.

Bioaugmentation, the addition of cultured microorganisms to enhance the currently existing microbial community, is an option to remediate contaminated areas. Several studies reported the success of the bioaugmentation method in treating heavy metal contaminated soil, but concerns related to the applicability of this method in real-scale application were raised. A comprehensive analysis of the mechanisms of heavy metal treatment by microbes (especially bacteria) and the concerns related to the possible application in the real scale were juxtaposed to show the weakness of the claim. This review proposes the use of bioaugmentation-assisted phytoremediation in treating heavy metal contaminated soil. The performance of bioaugmentation-assisted phytoremediation in treating heavy metal contaminated soil as well as the mechanisms of removal and interactions between plants and microbes are also discussed in detail. Bioaugmentation-assisted phytoremediation shows greater efficiencies and performs complete metal removal from soil compared with only bioaugmentation. Research related to selection of hyperaccumulator species, potential microbial species, analysis of interaction mechanisms, and potential usage of treating plant biomass after treatment are suggested as future research directions to enhance this currently proposed topic.

Ecological impacts of ballast water loading and discharge: insight into the toxicity and accumulation of disinfection by-products.

Since the implementation of the International Maritime Organization 2004 regulation, most ships have been equipped with on-dock ballast water treatment. While this method is effective in solving the invasive alien species problem, concerns are raised due to the potential release of disinfection by-products (DBPs) as the result of the chemical treatment. This review paper aims to summarize the history of ballast water management (BWM) and the currently used on-dock technology. Chlorination, oxidation, and ozonation are highlighted as the most currently applied methods to treat ballast water on-dock. This paper then focuses on the potential release of toxic DBPs as the result of the selected corresponding treatment methods. Tri-halo methane, haloacetic acid, and several acetic acid-related compounds are emphasized as toxic DBPs with concentrations reaching more than 10 µg/L. The potential toxicities of DBPs, including acute toxicity, carcinogenicity, genotoxicity, and mutagenicity, to aquatic organisms, are then discussed in detail. Future research directions related to the advanced treatment of DBPs before final discharge and analysis of DBPs in coastal sediments, which are barely studied at present, are suggested to enhance the current knowledge on the fate and the ecological impact of BWM.

Integrated emergent-floating planted reactor for textile effluent: Removal potential, optimization of operational conditions and potential forthcoming waste management strategy.

Native emergent and floating plants; local reed grass (Phragmites karka) and water hyacinth (Eichhornia crassipes), respectively, were used to treat textile wastewater using an integrated emergent-floating planted reactor (IEFPR) system at hydraulic retention times (HRTs) of 8, 14, and 19 days. Real textile effluent having characteristics of 1686.3 ADMI for colour, 535 mg/L for total suspended solid (TSS), 647.7 mg/L for chemical oxygen demand (COD) and 124 mg/L for biochemical oxygen demand (BOD) was used throughout this study. The IEFPR system experienced maximum removal of colour (94.8%, HRT 14 days, day 3), TSS (92.7%, HRT 19 days, day 7), and COD (96.6%, HRT 8 days, day 5) at different HRT and exposure time. The process conditions (HRT and exposure time) were optimized for maximum colour, TSS and COD removal from textile effluent by employing response surface methodology (RSM). The optimization has resulted 100% removal of colour, 87% removal of TSS and 100% removal of COD at HRT of 8 days and exposure time of 5 days, with 0.984 desirability. The integrated plant-assisted treatment system showed reliable performance in treating textile wastewater at optimum operational conditions to improve effluent quality before disposal into water bodies or being recycled into the process. The potential of phytoremediator (produced plant biomass) to be utilized as resources for bioenergy or to be converted into value added products (adsorbent or biochar) provides an alternative to management strategy for better environmental sustainability.

Comparative performance of Scirpus grossus for phytotreating mixed dye wastewater in batch and continuous pilot subsurface constructed wetland systems.

Dye is one of the pollutants found in water bodies because of the increased growth of the textile industry. In this study, Scirpus grossus was planted inside a constructed wetland to treat mixed dye (methylene blue and methyl orange)-containing wastewater under batch and continuous modes. The plants were exposed to various concentrations (0, 50, 75, and 100 mg/L) of mixed dye for 72 days (with hydraulic retention time of 7 days for the continuous system). Biological oxygen demand, chemical oxygen demand, total organic carbon, pH, temperature, ionic content, and plant growth parameters were measured. Results showed that S. grossus can withstand all the tested dye concentrations until the end of the treatment period. Color removal efficiencies of 86, 84, and 75% were obtained in batch mode, whereas 90%, 85%, and 79% were obtained in continuous mode for 50, 75, and 100 mg/L dye concentrations, respectively. Fourier-transform infrared analysis confirmed the transformation of dye compounds after treatment and scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy analysis showed that most of the intermediate compounds were not absorbed into plants but adsorbed onto the surface of the root structure.

Treatment technologies for bakers' yeast production wastewater.

Researchers in recent years have utilized a broad spectrum of treatment technologies in treating bakers' yeast production wastewater. This paper aims to review the treatment technologies for the wastewater, compare the process technologies, discuss recent innovations, and propose future perspectives in the research area. The review observed that nanofiltration was the most effective membrane process for the treatment of the effluent (at >95% pollutant rejection). Other separation processes like adsorption and distillation had technical challenges of desorption, a poor fit for high pollutant load and cost limitations. Chemical treatment processes have varying levels of success but they are expensive and produce toxic sludge. Sludge production would be a hurdle when product recovery and reuse are targeted. It is difficult to make an outright choice of the best process for treating the effluent because each has its merits and demerits and an appropriate choice can be made when all factors are duly considered. The process intensification of the industrial-scale production of the bakers' yeast process will be a very direct approach, where the process optimisation, zero effluent discharge, and enhanced recovery of value-added product from the waste streams are important approaches that need to be taken into account.

A feasibility study for the treatment of 1,2-dichloroethane-contaminated groundwater using reedbed system and assessment of its natural attenuation.

A reedbed system planted with Phragmites australis was implemented to treat chlorinated hydrocarbon-contaminated groundwater in an industrial plant area. Reedbed commissioning was conducted from July 2016 to November 2016 to treat contaminated groundwater via a pump-and-treat mechanism. Combination of horizontal and vertical reedbed systems was applied to treat 1,2-dichloroethane (1,2 DCA) under four parallel installations. The 2-acre horizontal and vertical reedbed systems were designed to treat approximately 305 m3/day of pumped groundwater. Initial concentration of 1,2 DCA was observed at 0.362 mg/L to 4320 mg/L, and the reedbed system successfully reduced the concentration up to 67.9%. The average outlet concentration was measured to be 2.08 mg/L, which was lower than the site-specific target level of 156 mg/L. Natural attenuation analysis was conducted using first-order decay kinetics, showing an average natural attenuation rate of 0.00372/year. Natural attenuation of 1,2 DCA was observed in shallow monitoring wells, which was indicated by the reduction trend of 1,2 DCA concentration, thereby confirming that the reedbed system worked well to remove 1.2 DCA from contaminated groundwater at the shallow profile.

What compound inside biocoagulants/bioflocculants is contributing the most to the coagulation and flocculation processes?

Biocoagulants and bioflocculants are alternative items that can be used to substitute the utilization of common-chemical coagulants and flocculants. Biocoagulants/bioflocculants can be extracted from animals, microorganisms, and plants. Moreover, biocoagulants/bioflocculants have specific characteristics that contribute to the coagulation and flocculation processes. The active compounds inside biocoagulants/bioflocculants vary and correspond to the specific working mechanisms, including charge neutralization, sweep coagulation, adsorption, bridging, and patch flocculation. This review paper summarizes the characteristics of biocoagulants/bioflocculants from different sources and its performance in treating various pollutants. Furthermore, this paper discusses the most contributing compounds and functional groups of biocoagulants/bioflocculants that can be related to their working mechanisms. Several functional groups and compounds in biocoagulants/bioflocculants are highlighted in this review article, as well as the correlation between the highlighted groups/compounds to the aforementioned coagulation-flocculation mechanisms. In addition, current knowledge gaps in the study of biocoagulants/bioflocculants and future approaches that may serve as research directions are also emphasized. This review article is expected to shed information on the characteristics of biocoagulants/bioflocculants, which may then become a focus in the optimization to obtain higher performance in future application of coagulation-flocculation processes.

Contaminants of emerging concern (CECs) in aquaculture effluent: Insight into breeding and rearing activities, alarming impacts, regulations, performance of wastewater treatment unit and future approaches.

The contamination of aquaculture products and effluents by contaminants of emerging concern (CECs) from the direct chemical use in aquaculture activities or surrounding industries is currently an issue of increasing concern as these CECs exert acute and chronic effects on living organisms. CECs have been detected in aquaculture water, sediment, and culture species, and antibiotics, antifoulants, and disinfectants are the commonly detected groups. Through accumulation, CECs can reside in the tissue of aquaculture products and eventually consumed by humans. Currently, effluents containing CECs are discharged to the surrounding environment while producing sediments that eventually contaminate rivers as receiving bodies. The rearing (grow-out) stages of aquaculture activities are issues regarding CECs-contamination in aquaculture covering water, sediment, and aquaculture products. Proper regulations should be imposed on all aquaculturists to control chemical usage and ensure compliance to guidelines for appropriate effluent treatment. Several techniques for treating aquaculture effluents contaminated by CECs have been explored, including adsorption, wetland construction, photocatalysis, filtration, sludge activation, and sedimentation. The challenges imposed by CECs on aquaculture activities are discussed for the purpose of obtaining insights into current issues and providing future approaches for resolving associated problems. Stakeholders, such as researchers focusing on environment and aquaculture, are expected to benefit from the presented results in this article. In addition, the results may be useful in establishing aquaculture-related CECs regulations, assessing toxicity to living biota, and preventing pollution.