Biotreatment Of Wastewater Research Articles

Biochar immobilized petroleum degrading consortium for enhanced granulation and treatment of synthetic oil refinery wastewater

This study investigated the effect of biochar immobilized consortium for enhanced biotreatment of oil refinery wastewater in sequencing batch reactors. The control reactor (R0), and reactors with free bacterial consortium (R1), biochar (R2) and biochar immobilized consortium (R3) were operated in parallel. Results illustrated that granulation was faster in R2 and R3, the proportion of granules >0.45 mm was almost 30% higher than the R0 and R1 during the first 45 days. R3 exhibited optimum operational performance as highest removal efficiencies of COD (97.9%), oil (97.4%), NH4+-N (97.2%) and TN (90.2%) at the end of the experiment. Biochar enriched microbial richness and diversity whereas inoculated consortium positively modulated the community structures. Higher abundance of inoculated Rhodococcus (4.81%) bacteria in R3 suggested successful formation of functional strains in the granular sludge. It concludes that the application of biochar immobilized consortium is a better choice for the treatment of refinery wastewater.

Re-evaluation of the environmental hazards of nZnO to denitrification: Performance and mechanism

Numerous studies have shown that zinc oxide nanoparticles (nZnO) have an inhibitory effect on wastewater biotreatment, where doses exceeding ambient concentrations are used. However, the effect of ambient concentrations of ZnO (<1 mg/L) on anaerobic digestion processes is not clear. Herein, this study comprehensively explored the impact of nZnO on the denitrification performance and core microbial community of activated sludge under ambient concentrations. Results showed that only 0.075 mg/L nZnO had shown a beneficial effect on nitrogen removal by activated sludge. When nZnO concentration reached 0.75 mg/L, significant enhancement of nitrate reduction and mitigation of nitrite accumulation were observed, indicating a remarkable stimulatory effect on nitrogen removal. Simultaneously, nZnO could weaken the sludge surface charge and improve the secretion of extracellular polymeric substances, thus enhancing sludge flocculation for denitrification. Microbial community analysis revealed that nZnO exposure increased the relative abundance of denitrifying bacteria, which could contribute to the reinforcement of traditional denitrification. Furthermore, exogenous addition of NH4+ significantly inhibited the accumulation of nitrite, implying that nZnO had a potential to improve the denitrification process via a partial denitrification-anammox pathway. Considering current ambient concentration, the stimulatory effect shown in our work may better represent the actual behavior of ZnO in wastewater biotreatment.

Evolution of the Urban Wastewater Bio-treatment and Reuse System of East Kolkata Wetlands, India: an Appraisal

Evolution of the Urban Wastewater Bio-treatment and Reuse System of East Kolkata Wetlands, India: an Appraisal

The Impact of Bioaugmentation on the Performance and Microbial Community Dynamics of an Industrial-Scale Activated Sludge Sequencing Batch Reactor under Various Loading Shocks of Heavy Oil Refinery Wastewater

The stable and efficient operation of the activated sludge sequencing batch reactor (ASSBR) in heavy oil refineries has become an urgent necessity in wastewater biotreatment. Hence, we constructed a green and efficient solid bioaugmentation agent (SBA) to enhance the resistance of the reactor to loading shock. The impact of bioaugmentation on the performance and microbial community dynamics under three patterns of heavy oil refinery wastewater (HORW) loading shock (higher COD, higher toxicity, and higher flow rate) was investigated on an industrial-scale ASSBR. Results showed that the optimal SBA formulation was a ratio and addition of mixed bacteria Bacillus subtillis and Brucella sp., of 3:1 and 3.0%, respectively, and a glucose concentration of 5.0 mg/L. The shock resistance of ASSBR was gradually enhanced and normal performance was restored within 6–7 days by the addition of 0.2% SBA. Additionally, the removal efficiency of chemical oxygen demand and total nitrogen reached 86% and 55%, respectively. Furthermore, we found that Burkholderiaceae (12.9%) was replaced by Pseudomonadaceae (17.1%) in wastewater, and Lachnospiraceae (25.4%) in activated sludge was replaced by Prevotellaceae (35.3%), indicating that the impact of different shocks effectively accelerated the evolution of microbial communities and formed their own unique dominant bacterial families.

Enhanced Bioremediation of Heavy Metals from Phosphate Processing Wastewater Using the Indigenous Bacterium Serratia rubidaea NCTC12971

Bioremediation using microorganisms have become innovative efficient tools for detoxifying a wide variety of urban and industrial wastewaters. In this study, we investigated for the first time the microbial detoxification of phosphate processing wastewaters (PPWW) by using the indigenous bacterium Serratia rubidaea NCTC12971, having numerous plant growth promoting traits. In fact, the isolated strain exhibited an attractive capacity of phosphate solubilization, siderophore production as well as indole acetic acid (IAA) secretion. Additionally, the strain has significant antifungal effect against Alternaria alternata. The monitoring of the bacterial growth at increasing concentrations of heavy metals showed minimum inhibitory concentrations (MICs) of 8, 6, 3 and 3 mg L−1, respectively for Pb, Cd, Cu and Zn. The 10-days treatment of PPWW by Serratia rubidaea significantly decreases its salinity in terms of electrical conductivity (EC), its chemical oxygen demand (COD), its biochemical oxygen demand (BOD5) and its total organic carbon (TOC). Regarding heavy metals removal, the detoxification rates were 94.4, 91.5, 85, and 66.5%, for Pb, Cd, Cu, and Zn, respectively. Moreover, the biological treatment of the PPWW declines its phytotoxicity toward lentils (Lens culinaris) and chickpea (Cicer arietinum) seeds germination. Hence, with the PPWW, the germination indices (GI) of chickpea (Cicer arietinum) and lentils (Lens culinaris) were 16.6 and 10%, respectively. While, with the biological treated (BTPPWW), the GI were significantly increased to approximately 76.6% for both seeds mentioned. Such results strengthened the potential use of Serratia rubidaea NCTC12971 for the establishment of biotechnological process aiming to minimize the harmful effects of PPWW as well as its use as plant growth promoting bacteria (PGPB). Highlights This study is the first report investigating the potential use of indigenous bacteria in the bio-treatment of wastewaters discharged from the Tunisian phosphate laundries units. Serratia rubidaea NCTC12971 was selected as a potent applicant for heavy metals detoxification. Serratia rubidaea NCTC12971 was characterized by its plant growth promoting traits and antifungal activity against Alternaria alternata.

Bioprocess performance, transformation pathway, and bacterial community dynamics in an immobilized cell bioreactor treating fludioxonil-contaminated wastewater under microaerophilic conditions

Fludioxonil is a post-harvest fungicide contained in effluents produced by fruit packaging plants, which should be treated prior to environmental dispersal. We developed and evaluated an immobilized cell bioreactor, operating under microaerophilic conditions and gradually reduced hydraulic retention times (HRTs) from 10 to 3.9 days, for the biotreatment of fludioxonil-rich wastewater. Fludioxonil removal efficiency was consistently above 96%, even at the shortest HRT applied. A total of 12 transformation products were tentatively identified during fludioxonil degradation by using liquid chromatography coupled to quadrupole time-of-flight Mass spectrometry (LC-QTOF-MS). Fludioxonil degradation pathway was initiated by successive hydroxylation and carbonylation of the pyrrole moiety and disruption of the oxidized cyanopyrrole ring at the NH-C bond. The detection of 2,2-difluoro-2H-1,3-benzodioxole-4-carboxylic acid verified the decyanation and deamination of the molecule, whereas its conversion to the tentatively identified compound 2,3-dihydroxybenzoic acid indicated its defluorination. High-throughput amplicon sequencing revealed that HRT shortening led to reduced α-diversity, significant changes in the β-diversity, and a shift in the bacterial community composition from an initial activated sludge system typical community to a community composed of bacterial taxa like Clostridium, Oligotropha, Pseudomonas, and Terrimonas capable of performing advanced degradation and/or aerobic denitrification. Overall, the immobilized cell bioreactor operation under microaerophilic conditions, which minimizes the cost for aeration, can provide a sustainable solution for the depuration of fludioxonil-contaminated agro-industrial effluents.

Applying hybrid genetic and artificial bee colony algorithms to simulate a bio-treatment of synthetic dye-polluted wastewater using a rhamnolipid biosurfactant

The present work aims at optimization and advanced simulation of removal efficiency of dye material from a synthetic wastewater using a locally generated rhamnolipid (RL) biosurfactant. For this purpose, bio-treatment of dye polluted synthetic wastewater was experimentally, kinetically, and statistically investigated by the ion flotation process in the presence of the RL. The removal rate of methylene blue (MB) as the dye material was assessed by the ultraviolet (UV)-visible absorbance measurements. The impact of operating variables including RL concentration (as a dye collector, 5–50 ppm), methyl isobutyl carbinol (MIBC) dosage (as a frother, 10–70 ppm), solution pH (2–12) and aeration rate (1–5 l/min) were assessed through one-way analysis of variance (ANOVA) and Anderson-Darling as the normality analysis strategy. The process was simulated using two artificial neural network (ANN) optimization algorithms, i.e., genetic algorithm (GA) and artificial bee colony (ABC) as a novel approach. The statistical results indicated that the dye removal process was significantly influenced by all operating variables (pvalue<0.05) while their relative intensity followed the order of aeration rate > solution pH > RL concentration > MIBC dosage. Anderson-Darling approach disclosed that the all factors were perfectly followed the normal trend with A2 less than unity and p-value of greater than 0.05 at 95% confidence level. Main effect plots revealed that except MIBC dosage with nonlinear trend, the rest of factors had an ascending influence on the removal efficiency. The process was optimized by interpreting the interaction effect among various variables to reach the maximum dye bioflotation. The maximum removal of 97 ± 0.13% was achieved at pH 12, airflow rate of 5 l/min, MIBC and rhamnolipid concentrations of 30 and 40 ppm, respectively with a flotation kinetic rate of 0.015 sec−1. Finally, the intelligent simulation results showed that the process could be modelled using an artificial bee colony algorithm of 4-7-1 structure with 99% and 98.8% accuracies in the training and testing steps, respectively. Further, we found that the artificial bee colony algorithm was superior to the genetic algorithm in terms of complexity analysis.

GCMS and FTIR spectral analysis of aqueous methylparathion biotransformation by the microbial mpd strains of Pseudomonas aeruginosa and Fusarium spp.

This study aimed to find out the effective biotreatment processes of aqueous methyl parathion in stipulations of its biotransformation by potential indigenous mpd strains of Pseudomonas aeruginosa and Fusarium spp. Microbial biotransformation study of methyl parathion in contaminated synthetic wastewater at optimum conditions by P. aeruginosa mpd-5 (at temperature 33°C, pH 7, under the aerobic condition with inoculum density of 108cells/mL) and by Fusarium spp mpd-1 (at temperature 30°C, pH 7, under the aerobic condition with inoculum density of 25mgL-1 dry biomass) was carried out. The major biodegradation compounds formed during the biotreatment process were analyzed by spectral studies using GCMS and FTIR. GCMS analysis of bacterial transformed compounds was p-nitrophenol, dimethylaminophenol, and glycyl-L-proline of 2-(3-methylpiperidino-4-5, 6-benzothiazin-4-one) and 2, 5-piperazinodione 3, 6-bis (2-methylpropyl). And the fungal transformed compounds were observed to be p-nitrophenol, phenol,2,4-Bis(1,1-Dimethylethyl), beta-L-arabinopyranoside-methyl, Cyclobutanethiol, 3-2(4)-thiophenone, dihydro-5-(1-methylethyl), Benzene,1,3-bis(1,1-dimethyl ethyl), Butanoic acid, 2-methyl methyl ester, and L-(+)-Ascorbic acid. The FTIR spectra of the molecule and the products of methyl parathion are observed to be changed in structures. It can be concluded from the aforementioned results and discussions that P. aeruginosa mpd-5 and Fusarium spp mpd-1 can be used in the biotreatment of pesticide wastewater having the high methyl parathion concentration and is possible by the indigenous microbial strains; they utilize as phosphate and carbon source of energy. Hence the strains can be used as a whole microbial cell, or its bioactive metabolites can be applied for the biotreatment of pesticide wastewater and potentially degrade methylparathion.

Simultaneous nitrification and denitrification of hypersaline wastewater by a robust bacterium Halomonas salifodinae from a repeated-batch acclimation

Biotreatment of hypersaline wastewater requires robust strains with high resistance to activity inhibition and even bacterium death, which remains a worldwide challenge. Here Halomonas salifodinae, a simultaneous nitrification and denitrification (SND) bacterium, was isolated by performing repeated-batch acclimation, showing efficient nitrogen removal at 0–15% salinity and low activity inhibition prominently superior to that of other strains such as Pseudomonas sp. and Acinetobacter sp. Community analysis as well as comparison of microbial activity at different salinities revealed an increased relative abundance of halotolerant populations by stimulating their salt tolerance during the repeated-batch process. For single or mixed nitrogen sources at 15% salinity, the SND efficiencies of the isolated strain reached above 95%. The high activities were attributed to the key enzymes AMO and HAO for nitrification as well as NAP and NIR for denitrification. The findings provide a promising acclimation pathway to obtain robust bacteria for biotreatment of hypersaline wastewater.

Removal of COD, TOC, and Color from Textile Industry Wastewater by Using Phanerochaete chrysosporium

Wastewater discharge from textile industries concern environmental risks. Superiority of microbial methods over other high cost combined methods includes conversion of persistent organic materials to non-toxic last materials, sustainability, low cost, and comfortable. Textile wastewaters can have opposite effects on the quality of water in total organic carbon (TOC) and Chemical oxygen demand (COD). Agitation cultures can reach the surface area of the dyes, whereas a static cannot do. Biotreatment of textile wastewater from the dyeing process using white-rot fungus Phanerochaete chrysosporium (P.C) was investigated in agitated and static culture conditions. Dye is the major pollutant component in this wastewater includes some different organic pollutants. The treatment mediums containing distilled water in 1:10 ratio of wastewater were compared for treatment efficiency of P.C. Especially in agitated conditions at 27 oC and 150 rpm, it was achieved a successful treatment results. Under these conditions, a 48h long treatment reduced by 91,46 % of the original COD (from 1484 mg l-1) and by 94,92% the TOC (initial was 723.66 mg l-1). Moreover, treatment reduced color by 86,28 % from 3.550 A540 to 0.487 A540 at the end of the study. The decolorization properties of P.C obtained high performance and we determined P.C showed up to effective removal rate for COD and TOC within 48 hours. We suggest that these fungus pellets of P.C can reach the decolorization and can be a useful tool for bioremediation of textile dye wastewater within a short time period.

Effect of coagulation on bio-treatment of textile wastewater: Quantitative evaluation and application

To address the challenge of high water consumption, massive wastewater discharge and high pollution risk in textile industries, different countries have chosen various treatment method for textile wastewater according to the location and management of textile enterprises. It is not economical purposely to build separate wastewater treatment plants (WWTPs) for each small-scale enterprise, hence, it is common to treat the wastewater for a group of factories and then complete the treatment via a municipal wastewater treatment plant. However, the complex characteristics of textile wastewater brings some new problems for WWTPs: Textile wastewater contains over 300 mg/L COD, 100 μg/L antimony, 1000 μg/L aniline, some of which are toxic to microbes or non-biodegradable. Coagulation plays an important role in the pretreatment of textile wastewater for removing hydrophobic dyes, decreasing the SS and COD. In this paper, Poly Ferric Sulfate (PFS), Poly Aluminum Chloride (PAC) and Poly Aluminum Ferric Chloride (PAFC) were chosen to improve the biodegradability of the textile wastewater. And then, quantitatively evaluate the biodegradability of wastewater before and after coagulation treatment by analyzing the proportion of different organic pollution, which could be divided into four parts including rapid bio-treated, easy bio-treated, normal bio-treated and non-biological treatment. Results showed that the biodegradability of textile wastewater could be improved by coagulation process, and the contents of organic matter of rapid bio-treated and easy bio-treated could be maximizing when the control condition of coagulation process was optimized. Moreover, because of its characteristics of simple, easy to use, and rapidly online implement, this approach holds a great promise for applications such as investigate wastewater feature deeply, treatment technology optimization, risk control and management.

Biotreatment of Effluent from Cassava Processing Using Powdered Seeds of Moringa oleifera

The world is facing increasingly more severe water security issues. It has, therefore, become imperative to develop sustainable, eco-friendly water management and recycling techniques. This study assessed the capacity of powdered seeds of Moringa oleifera to improve water quality of effluent from two (2) cassava processing plants in Umudike, Nigeria by measuring the variations in specific physicochemical and microbiological parameters of the samples. The biodegradability indices of the wastewater samples were determined as 0.513 and 0.507 for Plants 1 and 2 respectively indicating samples that were fairly biodegradable and treatable biologically. At the end of the 7-day study, turbidity reduced by 59.6% – 63.2% while chemical oxygen demand (COD), biochemical oxygen demand (BOD) and total organic carbon values dropped by 66.6% – 74.1%, 86.7% – 88.2% and 67.0% – 72.6% respectively. Correlation analysis showed a strong positive correlation between BO₅ and COD for both Plants 1 and 2. The total heterotrophic and coliform bacteria were completely removed by around day 5 of the study. The observed bacterial isolates in the effluent at onset were Escherichia coli, Bacillus sp., Klebsiella sp., Salmonella sp., Streptococcus faecalis, Shigella sp. and Aerobacter aerogenes. This study confirms the efficiency of powdered seeds of M. oleifera in biotreatment of wastewater from cassava processing plants.

Effects of green synthesized and commercial nZVI on crystal violet degradation by Burkholderia vietnamiensis C09V: Dose-dependent toxicity and biocompatibility

The increasingly common remedial application of nanoscale zero-valent iron (nZVI) to alleviate specific contaminant issues may inadvertently lead to nZVI accumulation in wastewater. This is a potential concern, because the effect of nZVI on the common microbes essential for wastewater biotreatment is not known. This is further complicated when there are many ways available to synthesize nZVI, which may interreact with bacteria differently. Thus, in this study, the different effects of nZVI synthesized by Eucalyptus leaves (EL-nZVI) and a commercially synthesized nZVI on the biodegradation of crystal violet by Burkholderia vietnamiensis C09V (B.V. C09V) was studied. At high dose (1000 mg/L), EL-nZVI and commercial nZVI both significantly inhibited the removal of crystal violet by B.V. C09V, decreasing removal rates by 10.5 and 13.1% respectively. Optical density (OD600) and soluble protein assays indicated that the growth of B.V. C09V improved under low doses (100 mg/L), but remained inhibited under high doses (500 and 1000 mg/L) of both commercial and EL-nZVI. Enzymes were also sensitive to nZVI, where the commercial variant exerted a greater effect on both the activity of lactate dehydrogenase (LDH) and superoxide dismutase (SOD) than EL-nZVI, indicating that EL-nZVI was less toxic than commercial nZVI. LIVE/DEAD staining also showed that the number of apoptotic cells was significantly higher when exposed to commercial nZVI rather than EL-nZVI. Furthermore, scanning electron microscopy (SEM) confirmed that direct contact between nZVI and cells at 1000 mg/L nZVI caused cell membrane disruption. Whereas, at 100 mg/L EL-nZVI, B.V. C09V grew better due to the formation of dense biofilms around the suspended EL-nZVI at a. Fourier transform infrared spectra (FTIR), confirmed an abundance of oxygen-containing functional groups on the surface of EL-nZVI which provided better biocompatibility than commercial nZVI. Overall, while dose was the most significant factor influencing nZVI toxicity, surface composition and morphology was also important. These new findings suggest chemical synthesis of metal nanoparticles should be replaced by biosynthetic routes to maintain viable microbial pollution during wastewater treatment.

A novel halophilic Exiguobacterium mexicanum strain removes nitrogen from saline wastewater via heterotrophic nitrification and aerobic denitrification

The utilization of halophilic bioresources is limited due to a lack of isolation and characterization work. A halophilic bacterium strain SND-01 of Exiguobacterium mexicanum was isolated in this study, which is the first report on its novel function in heterotrophic nitrification-aerobic denitrification (HN-AD). The strain SND-01 is slightly halophilic, surviving at 0 up to 9% (w/v) salinity. When utilizing ammonium, nitrate or nitrite as the sole nitrogen source in aerobic conditions, the isolated strain showed the maximum nitrogen removal rate of 2.24 ± 0.14 mg/(L·h), 3.63 ± 0.21 mg/(L·h) and 2.30 ± 0.23 mg/(L·h), respectively. Functional genes and key enzymes involved in heterotrophic-aerobic nitrogen transformations were characterized, establishing the pathway of HN-AD. The nitrogen removal via HN-AD is dependent on the C/N ratio, salinity and temperature. The halophilic Exiguobacterium mexicanum strain SND-01 shows a significant potential in biotreatment of saline wastewater in an easy and cost-effective way.

Aerobic sludge digestion is distinguishingly affected by the different entering pathways of zinc oxide nanoparticles

Zinc oxide nanoparticles (ZnO NPs) are widespread emerging pollutants raising global concerns about their influences on biological wastewater treatment processes. However, the impacts of ZnO NPs on aerobic sludge digestion that is a major sludge treatment process remain unknown. Herein, this study comprehensively investigated the key influences of ZnO NPs on aerobic digestion of waste activated sludge (WAS) and the potential mechanisms involved. Two different entering pathways, i.e., ZnO NPs directly entered into aerobic sludge digester and ZnO NPs initially entered into wastewater bio-treatment reactor, were tested to evaluate the different impacts. Compared to the control, ZnO NPs initially entering into wastewater bioreactor inhibited WAS degradation by 18.2 ± 0.1%, whereas ZnO NPs immediately entered into digester inhibited it by 29.7 ± 0.1%. This was accompanied by a similar decrease in inorganic nitrogen production and oxygen consumption. ZnO NPs exposure in wastewater bioreactor changed WAS characteristics in favor of solubilization in aerobic digestion. Modelling analysis indicated that ZnO NPs inhibited WAS hydrolysis, especially for their direct entering into aerobic digester. Correspondingly, microbial community was shifted in the direction against aerobic digestion by the ZnO NPs. Excessive oxidative stress and Zn2+ release represented the primary toxicity factors for the inhibition.

Simultaneous phycoremediation of petrochemical wastewater and lipid production by Chlorella vulgaris

A novel strategy of using microalgae Chlorella vulgaris for simultaneous bio-treatment of petrochemical wastewater and lipid production was developed in the present study. Phycoremediation was carried out in 30 days. The profile of fatty acids was identified, and the specifications of biodiesel including saponification value, iodine value, cetane number, long-chain saturated factor, cold filter plugging point, cloud point, allylic position equivalent and bis-allylic position equivalent were predicted by BiodieselAnalyzer® software. Besides, polycyclic aromatic hydrocarbons were determined in both wastewater samples and produced lipid. The observed data showed that biodiesel from C. vulgaris was superior to petrodiesel in terms of suitability in diesel engines. Moreover, contamination of petrochemical wastewater can influence the expression of a variety of genes in algae. To investigate the effectiveness of contamination on the expression of lipid synthesis as well as three photosynthesis genes, a real-time polymerase chain reaction assay was used to quantify transcript levels of PsaB (photosystem I reaction center protein subunit B), psbC (an integral membrane protein component of photosystem II), and rbcL (a large subunit of ribulose-1,5-bisphosphate carboxylase oxygenase). Furthermore, the gene expression level of accD (acetyl-coenzyme A carboxylase carboxyl transferase subunit beta, chloroplastic) was studied to discover the effect of wastewater on lipid production. The results showed that when diluted petrochemical wastewater (50%) was used as a media for C. vulgaris cultivation, these genes expression significantly increased. For 50% diluted wastewater, the maximum removal of BOD, COD, total nitrogen, and total phosphor has been 30.36%, 10.89%, 69.89%, and 92.59%, respectively.

Resource recovery in potato chips processing industry: green bioelectricity production using continuous mediatorless microbial fuel cell

ABSTRACT Potato chips processing industry generally discharge large volumes of organic loaded-wastewater and significant amounts of peels as solid wastes. In this study, a dual chamber microbial fuel cell (MFC) was setup, and continuously operated for 120 days for combined biotreatment of potato chips processing wastewater (PCW) and waste potato peels (PP) associated with electricity generation. The discarded PP were dried, grinded, and added to the PCW as a powder at concentrations of 0, 2.5, and 5 g PP/L resulted in three different organic loadings, denoted as OL0, OL1, and OL2, respectively. The results demonstrated significant removal efficiency of COD up to 99% with maximum power generation of 612.5, 800, and 1012.5 mW/m3 for OL0, OL1, and OL2, respectively. Butler–Volmer–Monod model was proposed to describe the overpotential-polarization curve for the MFC. Significant agreement was observed between the predicated and experimental results with determination coefficient (R2) values > 0.91.

Harvesting of Microalgae from Synthetic Fertilizer Wastewater by Magnetic Particles Through Embedding–Flocculation Strategy

Microalgae bio-treatment of synthetic fertilizer wastewater is particularly attractive due to their photosynthetic capabilities. Microalgae tend to convert solar energy into useful biomass, incorporating with the nutrients that present in wastewater, such as nitrogen and phosphorus. However, harvesting of microalgae remains a challenge because of the small size (3–30 μm) of microalgae cells and the repulsion between the negatively charged microalgae cells maintains a stable cell suspension. Magnetic-aided-embedding-flocculation strategy, which is one-step method by mixing microalgae, magnetic particles and flocculant together, is proposed for microalgae harvesting in order to meet cost and time effectiveness. In this study, the optimum cell separation efficiency of Chlorella vulgaris microalgae above 96% at 5 mg/L of chitosan dosage is achieved. With the aid of iron oxide particles, either micro- or nano-size, the sedimentation rate of cell flocs up to 250 cm/h is obtained when 10 mg/L of iron oxide is embedded into the cell flocs. The sedimentation rate with the embedding of iron oxide shows about 2 times faster than that of without magnetic particles. This strategy had proven effective for the polishing of the pretreated synthetic fertilizer wastewater by removing up to 53%, 74% and 70% of ortho-phosphate, nitrate and ammoniacal nitrogen, respectively. In addition, the presence of iron oxide particles and chitosan in microalgae harvesting that showed no adverse effect toward the quantity and quality of extracted lipid. This strategy is proven feasible for fertilizer wastewater treatment and biodiesel production.

Effect of immobilized anthraquinone-2-sulfonate on antibiotic resistance genes and microbial community in biofilms of anaerobic reactors

Quinone compounds could significantly accelerate anaerobic biotransformation of refractory pollutants. However, the effect of quinone compounds application on the propagation of antibiotic resistance genes (ARGs) in the bio-treatment of these pollutants-containing wastewater is not available. In this study, the catalytic performance of anthraquinone-2-sulfonate immobilized on polyurethane foam (AQS-PUF), changes of ARGs, mobile gene elements (MGEs) and microbial community structure attached on AQS-PUF and PUF in the up-flow anaerobic bioreactors were investigated. The results showed that AQS-PUF could significantly accelerate the decolorization of azo dye RR X–3B. Meanwhile, metagenomics analysis showed that the total absolute abundance of ARGs increased in the presence of the immobilized AQS. Among ARGs, the number of the efflux pump-encoding ARGs in the biofilm of AQS-PUF accounted for 35.7% of the total ARGs, which was slightly higher than that of PUF (32.1%) due to the presence of the immobilized AQS. The relative abundances of ARGs conferring resistance to MLS (macrolide, lincosamide and streptogramin), tetracycline and sulfonamide, which were deeply concerned, reduced 10%, 21.7% and 7.3% in the presence of the immobilized AQS, respectively. Moreover, the immobilized AQS resulted in the decreased relative abundance of plasmids, transposons and class I integrons. Among the detected 31 ARG subtypes located in MGEs, the relative abundances of only lnuF, msrE and mphD in the biofilm of AQS-PUF were over 2-fold higher compared with those in the biofilm of PUF. However, the three ARGs and their host Gammaproteobacteria was not dominant in microbial community. The relative abundances of more ARGs including MLS (lnuB and EreA), tetracycline (tetH) resistance genes located in MGEs decreased, which was attributed to the decreased relative abundance of their hosts. These studies showed that the addition of the immobilized AQS (around 0.25 mM) had a beneficial effect on reducing the spread of ARGs during dyeing wastewater bio-treatment.

Performance of microbial fuel cell operating with clay-manihot starch composite proton exchange membrane using RSM

This study optimized the performance of a microbial fuel cell (MFC) operating with raw clay sample (RCS)–manihot starch composite functioning as proton exchange membrane for electric power generation and bio-treatment of wastewater using central composite design (CCD) technique of the response surface methodology (RSM). The clay sample was heated at different temperatures ranging from 100 ​°C to 900 ​°C. The responses, power density and biochemical oxygen demand (BOD) removal efficiency were functions of four critical quantitative variables: pH, proton exchange membrane (PEM) preparation temperature (PPT), anolyte concentration and relative mass of clay in the PEM manihot-clay composite. A 24 CCD was employed to model and predict the process parameters. Sanitary wastewater of maximum cell density 4.25 ​× ​104/100 ​mL sustained the cell. Optimal responses of 82.4 ​mW/m2 power density and 72.3% BOD removal efficiency were recorded at clay PPT (RCS – 300 ​°C), 80 v/v wastewater to 10% glucose solution anolyte concentration, pH of 6.5 and clay component of PEM of mass 70 ​g optimum conditions. The study therefore suggests that RSM is an effective tool for evaluating and optimizing the Rsc-manihot composite PEM-MFC device for clean energy recovery and wastewater treatment, thereby providing the necessary leeway to overcoming the challenge of MFC scalability and greater performance.