Total Phosphorous Removal Research Articles

Effectiveness of agricultural waste in the enhancement of biological denitrification of aquaculture wastewater.

Nitrogen pollution in aquaculture wastewater can pose a significant health and environmental risk if not removed before wastewater is discharged. Biological denitrification uses external carbon sources to remove nitrogen from wastewater; however, these carbon sources are often expensive and require significant energy. In this study, we investigated how six types of agricultural waste can be used as solid carbon sources in biological denitrification. Banana stalk (BS), loofah sponge (LS), sorghum stalk (SS), sweet potato stalk (SPS), watermelon skins (WS) and wheat husk (WH) were studied to determine their capacity to release carbon and improve denitrification efficiency. The results of batch experiments showed that all six agricultural wastes had excellent carbon release capacities, with cumulative chemical oxygen demands of 37.74–535.68 mg/g. During the 168-h reaction, the carbon release process followed the second-order kinetic equation and Ritger-Peppas equation, while carbon release occurred via diffusion. The kinetic equation fitting, scanning electron microscopy, and Fourier transform infrared spectroscopy results showed that LS had the lowest cm and the maximum t1/2 values and only suffered a moderate degree of hydrolysis. It also had the lowest pollutant release rate and cumulative chemical oxygen demand, as well as the most efficient removal of total phosphorous (TP) and total nitrogen (TN). Therefore, we concluded that LS has the lowest potential risk of excess carbon release and capacity for long-lasting and stable carbon release. The WS leachate had the highest TN contents, while the SPS leachate had the highest TP content. In the 181-h denitrification reaction, all six agricultural wastes completely removed nitrate and nitrite; however, SS had the highest denitrification rate, followed by LS, WH, BS, SPS, and WS (2.16, 1.35, 1.35, 1.34, 1.34, and 1.01 mg/(L·h), respectively). The denitrification process followed a zero-order and first-order kinetic equation. These results provide theoretical guidance for effectively selecting agricultural waste as a solid carbon source and improving the denitrification efficiency of aquaculture wastewater treatment.

Coupling of Anaerobic Digestion and Struvite Precipitation in the Same Reactor: Effect of Zeolite and Bischofite as Mg2+ Source

The aim of this research was to assess the simultaneous effect of zeolite and bischofite on estruvite production in an anaerobic digester treating pig slurry as substrate. Three ratios (5:1, 6:1 and 7:1) of Mg-P were used for evaluating the effect of only bischofite on anaerobic digestion. For assessing the simultaneous effect of zeolite and bischofite on anaerobic digestion, three mass ratios of zeolite:bischofite (1, 5 and 10%) were used. As results, bischofite as Mg+2 source served to decrease the total phosphorous (TP) concentration in the anaerobic digestion of pig manure without affecting the maximum methane production rate or methane yield of the system. An average 82.5% TP removal was found in the reactors with bischofite during the first 5 days of digestion. Nevertheless, bischofite increased the lag-phase of the system. The simultaneous presence of zeolite and bischofite (1% ratio with respect to bischofite) caused a TP removal of 65.6% and increased the methane yield by up to 19.9% compared to a system without zeolite or bischofite. Thus, it is feasible to use bischofite and zeolite as enhancers for the simultaneous production of biogas and struvite inside an anaerobic digester treating piggery wastewater.

Purification efficiency of eight aquatic plant species in an artificial floating island system in relation to extracellular enzyme activity and microbial community

The floating island system exploits the combination of aquatic plants, microorganisms, and extracellular enzymes to purify wastewater. We investigated the purification efficiency of eight aquatic plant species cultured in wastewater. The relationships of plant purification capacity with extracellular enzyme activity and microbial community were analyzed to explore the crucial factors that affect the plant purification capacity and the mechanism of pollutants removal in different plant systems. Three plant species, namely Oenanthe javanica, Thalia dealbata, and lris pseudacorus, were most effective for purification of ammonium-nitrogen (NH4+-N), total phosphate (TP), and chemical oxygen demand (COD) with maximum efficiencies of 76.09, 85.87, and 89.10%, respectively. Urease, alkaline phosphatase (AP), and β-glucosidase activities were significantly and positively correlated with root system development (P < 0.05). Activities of urease and AP were positively correlated with NH4+-N and TP removal, respectively. The magnitude of urease and AP activity was generally consistent with the plant’s capacity to remove NH4+-N and TP. β-Glucosidase activity and COD removal were not significantly correlated. The dominant microbial phylum in each species treatment was Proteobacteria. Alphaproteobacteria and Bacteroidia showed > 1% relative abundance and greater involvement in degradation of pollutants in the experimental system.

Microalgae-based swine wastewater treatment: Strain screening, conditions optimization, physiological activity and biomass potential

Using microalgae to treat swine wastewater (SW) can achieve wastewater purification and biomass recovery at the same time. The algae species suitable for growth in SW were screened in this study, and the response surface combined with the desirability function method was used for multi-objective optimization to obtain high algal biomass and pollutant removal. Chlorophyll fluorescence parameters and biomass composition were analyzed to evaluate the cell physiological activity and its application potential. Chlorella sp. HL was selected as the most suitable species for growth in SW, and after 9 d of cultivation, the maximum specific growth rate and highest algal density were achieved 0.51 d−1 and 2.43 × 107 cells/mL, respectively. In addition, the removal of total phosphate and chemical oxygen demand were reached 69.13% and 72.95%, respectively. The optimum conditions for maximum algal density and highest pollutant removal were determined as the light intensity of 58.73 μmol/m2/s, inoculation density of 5.0 × 106 cells/mL, and a light/dark ratio of 3 using response surface model, and the predicted overall desirability value was 0.96. The potential maximum quantum yield of PSII (Fv/Fm) of Chlorella sp. HL in the early stage of cultivation was 0.60–0.70, while under high light and long photoperiod, the value of Fv/Fm and performance index of Chlorella decreased, trapped and dissipated energy flux per reaction center increased. The higher heating value of 18.25 MJ/kg indicated that the Chlorella cultivated in SW could be a good feedstock for biofuel production.

Performance evaluation of the integrated hydroponics-microbial electrochemical technology (iHydroMET) for decentralized domestic wastewater treatment

Here we report on the performance of the integrated drip hydroponics-microbial electrochemical technology (iHydroMET) for decentralized management of domestic wastewater at the household level. The study focused on optimizing the iHydroMET reactor components, followed by its performance evaluation for domestic wastewater treatment at different feed volumes. Based on the reactor components optimization work, granular activated charcoal:cocopeat (20:80) combination for bed matrix, 75% immersed cathode in effluent configuration, and Catharanthus roseus plant were selected for further experiments. The iHydroMET system with the optimized reactor components achieved efficient removal of organic matter (up to 93%) and turbidity (up to 98%) but minimal total nitrogen (<24%) and total phosphorous (<8%) removal after 24 h with 10 L of feed volume. It also removed the contaminants of emerging concern, such as sterols, at >95% efficiency. The UV-treated effluent (<2 MPN/100 mL) with considerable concentrations of N (∼34 mg/L) and P (∼5 mg/L) nutrients qualifies the standards for agricultural use and landscape irrigation purposes and contribute to lowering the burden on freshwater usage. The system also produced a power density of 30.3 mW/m2. Cultivation of evergreen C. roseus, a high aesthetic value ornamental and medicinal plant, further adds to ecological and environmental benefits of the iHydroMET technology. Further modifications in system operation like creating a saturation zone in the reactor units might improve the electric output and result in sufficient removal of nutrients, making the use of effluent for flushing and other purposes possible in households.

“Cattle dung biochar-packed vertical flow constructed wetland for nutrient removal”: Effect of intermittent aeration and wastewater COD/N loads on the removal process

The effect of varying COD/N ratio (1:1, 3:1, 5:1, 8:1, 10:1) of wastewater and intermittent aeration on treatment efficiency of biochar (BC)-packed (with 10% V/V biochar) vertical flow constructed wetland (VFCW), planted with Colocasia esculenta was assessed in this study. Three setups of VFCW were prepared in two sets: aerated (with an airflow rate of 1.0 ± 0.6 L min−1 for 6 h d−1) and non-aeration, and changes in COD, NH4+-N, NO3-N, TN, and TP (total phosphorous) in the effluent was investigated. In VFCWS with intermittent aeration, COD, NH4+-N, NO3-N, TP removal was 99.0, 97.0, 81.0, and 89.0%, significantly higher (p < 0.05) than non-aerated VFCW setups as 91.3, 70.9, 86.97 and 64.4%, respectively. In non-aerated VFCWs, BC addition in combination with plantation was advantageous in the nutrient removal process than setups without BC. COD/N ratio of wastewater did not show a significant impact on the working of VFCWs if amended with BC and intermittent aerations, suggesting slow adsorption rate and fast aerobic degradation of organic matter. The study suggests that oxygen supply management and BC addition in VFCWs could be an effective strategy to treat wastewater with a high organic load. Apart from that study results will be useful for refinement of the operational strategy with varying organic load.

Changes of microbial community structure during the initial stage of biological clogging in horizontal subsurface flow constructed wetlands

The clogging is a universal problem in constructed wetlands, where microorganisms play an essential role. However, the implication of micro-organism variation due to the clogging is not clear. Four horizontal subsurface flow constructed wetlands (HFCWs) were designed and operated to simulate the process of clogging. The wetland treatment performance and microbial community variation were investigated by regularly monitoring. Results showed the substrate filtration rate and the total phosphorous (TP) removal efficiency consistently decreased and the chemical oxygen demand (COD) and total nitrogen (TN) removal efficiency were at the range of 50%-85% and 10–20%, respectively. The sequencing results indicated that the clogging could affect the richness of bacterial community. The bacterial variation could be attributed to the dissolved oxygen decreasing and organic matter accumulation in the initial clogging period. These findings are expected to provide some theoretical reference for developing the biological methods to indicate the initial clogging in constructed wetlands.

Two moving bed biofilm reactors in series for carbon, nitrogen, and phosphorous removal from high organic wastewaters

Government regulations require on-site treatment of industrial wastewater prior to sewage discharge to prevent environmental degradation of receiving waterbodies. The sequencing batch moving bed biofilm reactor (SB-MBBR) can permit on-site treatment of high organic and nutrient content of cheese production wastewater. However, the critical challenge exists of maintaining both an active heterotrophic and an autotrophic population in a single biofilm system treating carbon and ammonia to low discharge levels from cheese production wastewater. Two SB-MBBRs in series separate the heterotrophic and autotrophic communities, circumventing the competition between the heterotrophic and autotrophic populations in a single biofilm system treating wastewater with high carbon to nitrogen ratios. The first reactor (AN/AE) was operated by cycling between anaerobic and aerobic stages to select for polyphosphate accumulating organisms, and the AN/AE reactor degraded carbon and phosphorous. The second reactor (NIT) was operated with aerobic conditions to promote nitrifying bacteria and treat total ammonia nitrogen. The performance of this system for carbonaceous constituents and ammonia was evaluated by quantifying the kinetics, biofilm morphology, thickness, dry-mass, and dry-density of the two SB-MBBR in series technology. The AN/AE reactor achieved 97.5 ± 1.7%, 58.8 ± 5%, and 49 ± 1% soluble chemical oxygen demand, total nitrogen, and total phosphorous removal efficiencies respectively. The NIT reactor achieved 98.7 ± 2.4 % total ammonia nitrogen removal, though partial nitritation at rates of 1.09 ± 0.03 g-N·m-2d-1, indicating this system can be incorporated in an anammox system. The study demonstrates that enhanced biological phosphorous removal, and potentially anaerobic removal of ammonia can be achieved for on-site treatment of cheese production wastewater.

Comparing the performance of the conventional and fixed-bed membrane bioreactors for treating municipal wastewater.

Membrane bioreactor (MBR) is relatively a new technology in wastewater treatment. It can efficiently remove soluble and suspended organics. However, it may constantly encounter bio-fouling and cannot efficiently remove nutrient pollutants. These two deficiencies have motivated researchers to upgrade the design and operation of conventional MBR (CMBR). This study evaluates the performance of hybrid fixed bed MBR (FBMBR) treating real domestic wastewater in different operational conditions. It also compares the experimental results of FBMBR with the CMBR. For this purpose, two identical reactors are constructed as CMBR and FBMBR. Each module contains the net volume of 140L and is operated continuously in two aerobic (DO > 4mg/L) and anoxic (DO < 1mg/L) conditions with average organic loading rates (OLRs) of 0.58, 0.71 and 1.55 kgCOD/m3d. The pore sizes of flat sheet membranes are 0.2-0.8μm with total surface area of 1.4m2 per module. The experimental results revealed that the removal efficiencies of BOD, COD and TSS are above 95 % in both CMBR and FBMBR in all operating conditions. However, fouling occurs with lower rates in FBMBR. The growing rate of transmembrane pressure (TMP) in aerobic condition is 1.7mBar/day in CMBR, while it reduces to 1.2mBar/day for FBMBR in solid retention time (SRT) of 75 days and OLR of 0.58 and 0.71 kgCOD/m3d. In anoxic condition with SRT of 100 days and OLR of 1.55 kgCOD/m3d, the TMP in FBMBR is 59 % of CMBR. In addition, total nitrogen (TN) removal is between 12 % (aerobic) and 27 % (anoxic) in CMBR, while it is between 25 % (aerobic) and 49 % (anoxic) in FBMBR. Total phosphorous (TP) removal also ranges between 50 and 66 % in CMBR, while it is between 51 and 86 % in FBMBR. Consequently, using hybrid systems of FBMBR can reduce membrane fouling rate and improve nutrient removal efficiency in comparison with CMBR. This approach can reinforce the biological treatment efficiency and preserve permeate quality in higher OLRs or in lower DO level.

Effect of Fe3+ on the sludge properties and microbial community structure in a lab-scale A2O process.

During biological wastewater treatment, ferric salt (Fe3+) usually serves as an inorganic flocculant to improve the agglomeration and sedimentation of suspended solids, and thus the removal efficiency of pollutants to meet the increasing strictly regulated wastewater discharge standards. In this study, we investigated the effects of Fe3+ on the removal efficiencies of pollutants, sludge properties, dominant flora and metabolic pathways of bacterial community in a classical anaerobic-anoxic-oxic (A2O) process. The results showed that a Fe3+ concentration lower than 10mg·L-1 could improve the removal efficiencies of chemical oxygen demand (COD) and total nitrogen (TN), while an inhibition effect was exerted at concentration higher than 10mg·L-1. The maximum removal efficiencies of COD and TN were 97% and 89%, respectively, under the critical Fe3+ concentration of 10mg·L-1. Total phosphorous (TP) removal was constantly positively correlated with Fe3+ concentration, due to the enhanced adsorption of phosphorus on activated sludge with the increase of surface roughness. Thauera displayed the highest relative abundance, and certain bacteria in Proteobacteria, Dehloromonas and Candidatus-Competibacter exhibited good adaptability to high concentration of Fe3+. In the context of metabolic collaterals, the most abundant functional gene families were identified to be Carbohydrate Metabolism, Amino Acid Metabolism, Cell Motility, Membrane Transport, and Replication and Repair. This study provides an extensive mechanistic insight into the impact of Fe3+ on the A2O process, which is of fundamental significance to exploit the contributions of inorganic salts to biological wastewater treatment.

Microalgal Co-cultivation for Biofuel Production and Bioremediation: Current Status and Benefits

Microalgae have been reported to exhibit mutualistic interactions with other microorganisms like bacteria, filamentous fungi, and yeast and help each other co-exist. The potential of microalgae to perform photosynthesis and accumulate lipids make them suitable candidates for lipid production. Biofuel production from various single oleaginous microorganisms is already in practice. However, the high cost of biomass harvesting, extraction of lipids, and contamination issues are significant challenges of biofuel bioprocess commercialization. Recent microalgal co-culture studies showed considerable potential for easy biomass harvesting and reduction in overall energy consumption cost. Therefore, microalgal co-culture could be an alternative to overcome these constraints and enhance biomass and lipid production. Additionally, the integration of the nutrient sequestration process from potential agro-industrial wastewater using microalgal co-culture can reduce the cost of the substrate requirement for cultivation as well as ecological load. The co-culture in wastewater has shown excellent total phosphate removal efficiencies by microalgae Chlorella sorokiniana and yeast Rhodotorula glutinis, nitrogen removal by microalgae C. sorokiniana with activated sludge, and ammonium-nitrogen removal by C. vulgaris and fungi Aspergillus sp. co-culture. This review summarized the current advances towards biofuel and its value-added production from various microalgae co-culture and compared it with monoculture fermentation. It also includes some critical challenges of co-culturing for the economically viable bioprocess development for biofuel production. Furthermore, techno-economic analysis and life-cycle assessment of co-culture technology were also discussed for biofuel production feasibility from microalgal co-culture.

Light intensity alters the phytoremediation potential of Lemna minor.

Lemnaceae, i.e. duckweed species, are attractive for phytoremediation of wastewaters, primarily due to their rapid growth, high nutrient uptake rates, tolerance to a broad range of growing conditions and ability to expeditiously assimilate a variety of pollutants. Light is essential for plant growth, and therefore, phytoremediation. Nevertheless, the effect of light intensity remains poorly understood in relation to phytoremediation, a knowledge gap that impedes the development of indoor, fully controlled, stacked remediation systems. In the present study, the effect of light intensity (10-850μmolm-2s-1) on the phytoremediation potential of Lemna minor was assessed. Plants were grown on either an optimal growth medium (half-strength Hutner's) or synthetic dairy processing wastewater, using stationary axenic (100mL) or re-circulating non-sterile (11.7L) systems. The relative growth rate (RGR) of L. minor grown on half-strength Hutner's increased proportionally with increasing light intensity. In contrast, the RGR of L. minor grown on synthetic dairy wastewater did not increase with light over an intensity range from 50 to 850μmolm-2s-1. On synthetic dairy wastewater, total nitrogen and total phosphorous removal also remained unchanged between 50 and 850μmolm-2s-1, although L. minor protein content (% fresh weight) increased from 1.5 to 2% at higher light intensities. Similar results were obtained with the larger re-circulating system. The results demonstrate interactive effects of light intensity and wastewater composition on growth and phytoremediation potential of L. minor. The data imply that light intensities above 50μmolm-2s-1 may not necessarily confer benefits in duckweed wastewater remediation, and this informs engineering of stacked, indoor remediation systems.

Coagulation of phosphorous and organic matter from marine, land-based recirculating aquaculture system effluents

Saline effluents from marine land-based aquaculture production can neither be disposed in common municipal wastewater treatment plants, nor disposed as landfill. Furthermore, stricter environmental regulations require the reduction of phosphorous and organic matter levels from marine environment discharges to minimize eutrophication. Chemical coagulation with FeCl3 and AlSO4 is commonly used for removing phosphorous and suspended solids in wastewater treatment. The capacity of these coagulants for creating particle aggregations depends on the characteristics and chemistry of the treated wastewater, such as the ionic strength or mixing conditions. Marine water has a higher ionic strength than fresh or brackish water, which may be beneficial when using chemical coagulants to treat the effluents from farms operated at high salinities. The following study compared the application of FeCl3 and AlSO4, to treat the two effluents discharged from a marine land-based recirculating aquaculture system (RAS) producing salmon (Salmo salar). The aim of the study was to determine; 1) in what effluent (sludge flow vs. exchange water overflow) at the end-of-pipe treatment the coagulant application is more efficient for the removal of PO43−-P, total suspended solids (TSS), total phosphorous (TP) and total chemical oxygen demand (TCOD); and 2) the optimal coagulant dose to apply and its associated chemical sludge production. The results show that more than 89 % removal of TCOD, TSS and TP is achieved when treating the sludge flow, arguably because the sludge flow contained the largest fraction of the target masses (P and organic matter) discharged from the system. Up to 80 % of TSS removal was achieved by simple sedimentation, and with the highest coagulant dose tested, up to 95 % of TSS could be removed from the effluent. To remove 90 % of PO43−-P, FeCl3 and AlSO4 need to be dosed at a molar ratio of 2.6:1 Fe:PO43−-P and 5.7:1 Al: PO43−-P, respectively. Dosing above 90 % removal efficiency did not significantly affect removal of PO43-P and TSS, but substantially increased the volume of chemical sludge produced. Finally, FeCl3 is proposed as a better overall alternative for P removal at the end-of-pipe treatment in marine land-based RAS.

Slaughterhouse Wastewater Treatment By Anodic Oxidation Using Two Different DSA-Type Anodes

Water is an essential resource for life, the environment and the industrial development; hence the treatment of wastewater has become crucial to ensure a good quality effluent before disposal the municipal sewer systems. The slaughterhouse industry produces a large volume of wastewater due to the slaughtering of animals, meat processing and the cleaning of the slaughterhouse facilities [1]. Treatment and adequate disposal of slaughterhouse wastewater (SW) is a worldwide economy and public health necessity which is regulated by International Standard [2]. SW contains elevated amounts of organic matter and salts. Typical parametrical analyses include pH, chemical oxygen demand (COD), biochemical oxygen demand (BOD), total nitrogen (TN), total phosphorous (TP), total organic carbon (TOC) and total suspended solids (TSS) [3]. After preliminary treatment, where most large particles are removed, the coagulation-flocculation technology is the most used primary treatment. However, it produces secondary pollution. Nowadays, electrochemical processes such anodic oxidation (AO) have been considered an alternative technology for the treatment of SW due to its mild operation conditions, quite compact and easy operation and not secondary waste streams among others. AO may oxidize the organic pollutants via two different ways: i) directly oxidized, where electron transfer occurs at the anode surface (M) and/or ii) indirectly oxidized, where the organic pollutants are oxidized through the mediation of some species electro-generated in situ at the anode surface and/or agents in the bulk solution.In this study, a real beef slaughterhouse wastewater presented the following characteristics: TOC (1150 mg L–1), COD (4320 mg L–1), TP (25 mg L–1), TN (72.28 mg L–1), TSS (1433 mg L–1) at pH 7.18 and conductivity of 2.79 mS cm–1. Bright red color was observed at 416 nm (1.24 A.U.) and the presence of coliform bacteria was confirmed (> 1600 MPN). AO tests were carried out in a single open cell compartment in batch operation mode. 0.1 L of SW was introduced into the electrolytic cell with constant stirring to ensure mass transport of the oxidant specie towards/from the anode to the bulk. AO was assessed using two different dimensionally stable anodes (DSA) type anodes: i) Ti/IrO2/Ta2O5 coating (DSA-O2) ii) Ti/Ru0,3Ti0,7O2 (DSA-Cl2). AISI 304 stainless steel plate was used as cathode. The geometrical bare area of both, cathode and anode, was about 5 cm2, having a 1 cm of interelectrode gap. AO experiments were analyzed at different applied current densities (2, 10 and 20 mA cm–2) and supporting electrolyte (0.05 M Na2SO4; 0.05 M NaCl) in order to find the best operating conditions.This study focuses on TOC and COD removal as a function of the current density and the electrolysis time. Minimizing TOC and COD values is the main objective in SW treatment. However, TOC is the most important role to determine the organic compounds in SW. Figure 1 shows the TOC removal during five hours of electrochemical treatment utilizing the two different DSA-type anodes at the higher current density (j = 20 mA cm–2). As can be seen in Figure 1a), EO process using DSA-O2 without supporting electrolyte reached the maximum removal of total organic carbon at the end of the electrolysis time. Residual TOC concentration achieved 232.66 mg L–1 (79.77 % removal efficiency). Figure 1b) displays the TOC abatement from SW using DSA-Cl2 anode. Alike the DSA-O2 the best EO test was the one where not supporting electrolyte was added, the maximum TOC removal efficiency reached 78.62 % (245.89 mg L–1) unlike the other tests using supporting electrolyte.The best operating conditions were found at current density of 20 mA cm–2 without supporting electrolyte. TOC, COD and TP removal efficiency were 79.77% and 78.62 %; 89.22% and 79.4%; 96.0% and 64% using DSA-Cl2 (Ti/Ru0,3Ti0,7O2) and DSA-O2 (Ti/IrO2/Ta2O5), respectively. Moreover, a complete discoloration and disinfection were achieved. Electrochemical oxidation test at best operating conditions gave energy consumption and specific energy consumption values for TOC, COD and TP using DSA-Cl2 and DSA-O2 of 24.5 and 26.5 kW h m–3, 27.1 and 28.9 kW h kgTOC –1, 7.14 and 6.88 kW h kgCOD –1 and, 1531.25 and 1104.17 kW h kgTP –1, respectively.[1] Bustillo-Lecompte C.F., Mehrvar M., 2015. J. Environ. Manag. 161 287–302.[2] US Environmental Protection Agency. Final Rule; Federal Register. 2004;69(173):54476–54555.[3] Bustillo-Lecompte, C.F., Mehrvar, M., 2017. J. Clean. Prod. 141, 278–289. Figure 1

Isolation and screening of Tetradesmus dimorphus and Desmodesmus asymmetricus from natural habitats in Northwestern China for clean fuel production and N, P removal

Isolation and screening of microalgal species from natural habitats should be a continues work to discover effective species for biofuel generation and wastewater treatment. In the current study, microalgal species namely Tetradesmus dimorphus GEEL-04 and Desmodesmus asymmetricus GEEL-05 were isolated, identified, and assessed for growth kinetics, nutrients removal efficiency, and whole biomass composition. T. dimorphus showed higher growth (1.46 OD680nm) compared with D. asymmetricus (1.16 OD680nm), and both showed 99% total nitrogen and total phosphorous removal. T. dimorphus and D. asymmetricus accumulated higher protein content (40.02 and 45.10%), carbohydrate (31.91 and 24.64%), and lipid (15.41 and 24.16%), respectively. The FTIR spectra absorbance revealed different function groups in microalgal biomass available for biofuel generation. Elemental analysis of microalgal biomass showed high carbon content 50.13% and 43.01% for T. dimorphus and D. asymmetricus, respectively. Thermogravimetric analysis indicated ≥ 80% volatile content in both isolates. The fatty acid composition of both microalgal strains showed high palmitic acid and linoleic acid corresponding to high quality biodiesel. These results indicated that the T. dimorphus and D. asymmetricus could be potential candidates for high biocomponents accumulation and N, P removal.

Phycoremediation of X-ray developer solution towards silver removal with concomitant lipid production.

The present research is mainly focusing on the characterization of X-ray developer solution and its toxic tolerance studies with Desmodesmus armatus towards the phycoremediation studies for removal of pollutants, silver, and concomitant lipid production. The characterization results suggested the presence of 1.229±0.004g/l BOD, 27.29±0.230g/l COD with a silver content of 0.01791±0.000g/l. The tolerance and toxicity limits of with X-ray developer solution reveals the remarkable growth of microalgae in 3:1.dilution ratio of BBM in the X-ray developer solutions. The phycoremediation with 19 days period shown the noticeable results with a relative BOD (20.86%), COD (13.88%), with 57.10% corresponding total phosphorous removal. The phycoremediation also has proven better relative silver removal potential of 44.06% on the 19th day with concomitant 1.392% lipid production. Overall, the present study shows the potential phycoremediation strategy of hazardous X-ray developer solutions with possible concurrent lipid production through a sustainable approach.

A Microalgae-Methanotroph Coculture is a Promising Platform for Fuels and Chemical Production From Wastewater

Wastewater resource recovery facilities are major energy consumers in a community, as well as major contributors for greenhouse gas (GHG) emission. Although anaerobic digestion (AD) is widely employed in wastewater treatment to reduce the amount of solid organic waste and the sludge produced, the use of the produced biogas is mostly limited to heating and electricity generation, while the nutrient rich digestate still requires further treatment. In this work, we propose a waste-to-value (W2V) platform based on a microalgae-methanotroph coculture, which can convert AD-generated biogas into value-added products, while simultaneously removing nutrients from digestate. The platform takes advantage of the synergistic interactions within a microalgae-methanotroph coculture to achieve significantly improved productivity of microbial biomass and enhanced nutrient recovery performance. Using Chlorella sorokiniana – Methylococcus capsulatus (Bath) as the model coculture, we demonstrate that the coculture offers a highly promising platform for W2V technologies, which can efficiently recover energy (from CH4) and carbon (from both CH4 and CO2) to produce microbial biomass, while removing nutrients from wastewater to produce treated clean water. Compared to microalgae monoculture, the coculture achieved 120% improvement in biomass production, 71% and 164% improvement in total nitrogen and total phosphorous removal respectively, when the same amount of biogas was provided.

Enhanced Microalgae Growth for Biodiesel Production and Nutrients Removal in Raw Swine Wastewater by Carbon Sources Supplementation

In the present work, effect of two carbon sources, namely, sodium bicarbonate and sodium acetate, on the growth of Spirulina platensis, raw swine wastewater (RSW) nutrients removal, and lipid production efficiency was thoroughly investigated. Experimental results showed that maximum biomass concentration and total nitrogen (TN), total phosphorous (TP), and ammonium removal percentage of 1.70 g L−1, 91.24%, 87.44%, 100% were achieved, respectively, when sodium bicarbonate was supplemented to the RSW, which were significantly (p < 0.05) higher than that of the control. With regard to sodium acetate as extra carbon source, maximum biomass concentration and TN, TP, and ammonium removal percentage reached 2.18 g L−1, 85.72%, 87.02%, and 100%, respectively, which were notably enhanced compared to that of the control. Furthermore, saturated fatty acids and unsaturated fatty acids content in the obtained biomass ranged from 68.01–69.44% to 30.56–31.99%, respectively, and hexadecanoic acid, palmitoleic acid, octadecenoic acid and linoleic acid were found to be the major fatty acid components in the algal lipids. Thus, sodium bicarbonate and sodium acetate supplementation to RSW are technically feasible strategies to enhance Spirulina platensis growth for simultaneously nutrients removal and biodiesel production.

Constructed Wetlands in Latin America and the Caribbean: A Review of Experiences during the Last Decade

The review aims to report the state-of-the-art constructed wetlands (CW) in the Latin America and Caribbean (LAC) region not limited to national and local conditions. The aim is with a broader view, to bring updated and sufficient information, to facilitate the use of the CW technology in the different countries of LAC. Thus, 520 experiences extracted from the 169 reviewed documents in 20 countries were analyzed. According to the data, horizontal subsurface flow wetlands are the most reported CW in the region (62%), the second most common CW technology in the region is free water surface CW (17%), then vertical flow systems (9%), followed by intensified constructed wetlands (8%), and finally French systems (4%). The performance for nutrient removal is analyzed, finding that the mean of Chemical Oxygen Demand (COD), Total Nitrogen (TN), and Total Phosphorous (TP) removal efficiencies varies from 65% to 83%, 55% to 72%, and 30% to 84%, respectively. The results suggest a generally good performance for COD and TN removal, but a low performance for TP removal. Regarding plant species used for CWs, 114 different plant species were reported, being until now the most extensive report about plant species used in CWs in the LAC region.

Mixed culture microalgae removal for water quality improvement using chitosan

The presence of microalgae affects water quality and beneficial uses of surface freshwaters. Chitosan with proven potential for harvesting specific microalgae species from their culture medium to produce biofuels and bioproducts also appears promising for efficient removal of mixed microalgae species from surface freshwaters. The main focus of the present study was on removal of mixed microalgae species using chitosan as a coagulant to help improve water quality. Important operational parameters were optimized for economical microalgae removal. The microalgae cells, chlorophyll-a, total nitrogen, and total phosphorous removal efficiency were 82.06%, 89.90%, 69.32%, and 44.01%, respectively, at an optimum chitosan dose of 10 mg/L, pH 8, slow mixing time 7 min, slow mixing rate 30 rpm, and settling time of 15 min. The results show that chitosan coagulation efficiently removed mixed microalgae species from surface freshwater with significant improvement in water quality and recovery of algal biomass for other beneficial applications.