Pistia Research Articles

Silver Modified Hydrophytes for Heavy Metal Removal from Different Water Resources

Phytoremediation of three different aquatic plants powders Lemna minor L., Azolla filiculoides Lam. and Pistia stratiotes L. studied against different heavy metals (HM) and after modifications with interfacial layer synthesized silver nanoparticles. Prepared samples tested for the selective absorbance of chromium, cadmium, lead, and zinc. L. minor and P. stratiotes show selective absorption against lead, while Azolla filiculoides show higher absorption against chromium. Absorption of all heavy metal concentrations was found to be enhanced after interfacial modification with green synthesized silver nanoparticles.

Sustainable ecological engineering systems for the treatment of domestic wastewater using emerging, floating and submerged macrophytes

Water scarcity is perceived as a global systemic risk since there is an inexorable rise in water demand. An ecological engineering system mimics a natural ecosystem by balancing the trophic conditions for effective treatment of wastewater in a sequential manner. The present study was designed using emergent, floating and submerged macrophytic plants in a systematic approach. The study was evaluated with several components such as plants (water hyacinth, water lettuce and water thymes), aeration (supply of oxygen), and physical adsorption (activated carbon). Domestic wastewater collected from the local effluent treatment plant was treated individually and by combining all the components. Diverse experimental setups viz., lake sediment (control reactor), aeration, activated carbon blocks, water hyacinth, water lettuce, and water thymes were individually studied. Further the above components were combined, such as lake sediment + aeration + activated carbon blocks with plants like water hyacinth, water lettuce, and water thymes. The study inferred along with phytoremediation, and the external factors enhanced the treatment performances. Water hyacinth documented enhanced chemical oxygen demand removal efficiency of 85.71%, followed by water lettuce (80%), and water thymes (77.14%) along with the plants, both aeration, and activated carbon had stimulated the wastewater treatment. The highest removal efficiency of nitrate (70.23%), phosphate (63.64%), and sulphate (61.16%) were observed in water hyacinth due to its thick roots, and fibrous tissues reported effective treatment. The study hypothesized that these processes could be an effective strategy to restore the lakes and regulate the environmental flow. The study infers that an ecological engineering system symbiotically enables to self-organize the ecosystem within the boundary.

An experimental investigation on phytoremediation performance of water lettuce (Pistia stratiotes L.) for pollutants removal from paper mill effluent.

The present study describes the phytoremediation performance of water lettuce (Pistia stratiotes L.) for physicochemical pollutants elimination from paper mill effluent (PME). For this, pot (glass aquarium) experiments were conducted using 0% (BWW: borewell water), 25%, 50%, 75%, and 100% treatments of PME under natural day/light regime. Results of the experiments showed that the highest removal of pH (10.75%), electrical conductivity (EC: 63.82%), total dissolved solids (TDS: 71.20%) biological oxygen demand (BOD: 85.03%), chemical oxygen demand (COD: 80.46%), total Kjeldahl's nitrogen (TKN: 93.03%), phosphorus (P: 85.56%), sodium (Na: 91.89%), potassium (K: 84.04%), calcium (Ca: 84.75%), and magnesium (Mg: 83.62%), most probable number (MPN: 77.63%), and standard plate count (SPC: 74.43%) was noted in 75% treatment of PME after treatment by P.stratiotes. PCA showed the best vector length for TKN, Na, and Ca. The maximum plant growth parameters including, total fresh biomass (81.30±0.28g), chlorophyll content (3.67±0.05mgg-1 f.wt), and relative growth rate (0.0051gg-1 d-1 ) was also measured in 75% PME treatment after phytoremediation experiments. The findings of this study make useful insight into the biological management of PME through plant-based pollutant eradication while leftover biomass may be used as a feedstock for low-cost bioenergy production. PRACTITIONER POINTS: Biological treatment of paper mill effluent using water lettuce is presented. Best reduction of physicochemical and microbiological pollutants was attained in 75% treatment. Maximum production of chlorophyll, plant biomass, and highest growth rate was also observed in 75% treatment.

Utilisation potentials of invasive plants in the Owabi dam in the Ashanti region of Ghana

This paper provides a compendium of the utilisation potential of aquatic invasive plants found in the Owabi Dam in the Ashanti Region of Ghana. In total, seven aquatic invasive plants were identified in the Owabi Dam, which included Ceratophyllum demersum, Nymphaea odorata, Polygonum lanigerum, Arthropteris orientalis, Typha domingensis, Pistia stratiotes, and Cyprus papyrus. Some of the identified invasive plants were found to be highly nutritious and suitable for human consumption or use as feed for livestock, fish, and poultry. Other plants had high medicinal potential and aesthetic value. Several of the invasive plants were suitable for bio-industrial usages as feedstock to produce biofuels, insecticides, and biofertilizer, among other products. Therefore, if an effective utilization method of these currently unutilized aquatic invasive plants is established, it can provide a source of livelihood and income generation for individuals and households and contribute to controlling the impact of invasive plants on the Owabi Dam.

Different scales determine the occurrence of aquatic macrophyte species in a tropical stream

Distributions of aquatic macrophyte species are commonly associated with water chemistry characteristics. However, other environmental factors that can lead to the occurrence of aquatic plants in lotic ecosystems, such as dynamic habitats linked to the surrounding landscape, have been underestimated. This study aims to evaluate landscape features that may influence the occurrence of species of euhydrophyte aquatic macrophytes in a tropical river basin. We assessed the occurrence of the following seven species: Egeria densa, Cabomba furcata, Potamogeton pusillus, Potamogeton polygonus, Utricularia foliosa, Pistia stratiotes and Salvinia molesta. We also measured environmental variables related to three spatial scales, local (limnological), channel and riparian landscape, along 25.5 Km of the Itanhaém River basin (São Paulo, Brazil). We found that local (limnological) and channel characteristics were important variables in determining the occurrence of aquatic macrophyte species while the landscape scale had little influence on species composition. Channel depth and margin slope were especially relevant abiotic variables in explaining the occurrence of four of the species but not P. pusillus, P. polygonus and U. foliosa. Our results highlight the importance of channel morphology for understanding aquatic plant occurrence and community composition in tropical rivers.

Implications of global climate change for the development and ecological interactions between two key Amazonian aquatic macrophytes

ABSTRACT Amazon wetlands are among the most vulnerable ecosystem to be impacted by climate change, which may increase the frequency of extreme droughts and floods. We used Eichhornia crassipes and Pistia stratiotes, two abundant aquatic plants in the Amazon floodplains, to evaluate the effects of combined temperature and [CO2] increase on growth, physiology and ecological interactions. Individual and paired plants were deposited for three weeks in a microcosm under four IPCC scenarios: control (current temperature/CO2), mild (control + 1.5 oC, 200 ppm CO2), intermediate (control + 2.5 oC, 450 ppm CO2) and extreme (control + 3.5 oC, 850 ppm CO2). P. stratiotes died after three weeks in the intermediate and extreme treatments; E. crassipes experienced no mortality or change in any of the measured variables during the same period. P. stratiotes reduced root length in the mild treatment and reduced total dry biomass in intermediate and extreme treatments, revealing less tolerance to climate change. Ecological interactions between the two species changed with increasing [CO2] and temperature neutral interaction changed to facilitation for E. crassipes, while competitive interaction changed to neutral for P. stratiotes. Global climate change may alter the composition, biomass and ecological interactions of Amazonian aquatic plant species.

Comparative analysis of fresh and dry free-floating aquatic plant Pistia stratiotes via chemical pretreatment for second-generation (2G) bioethanol production

In the effort to manage global warming and fossil carbon emissions, many countries are suggesting brand-new policies to make their energy matrix much more renewable. The boost share of bioethanol as a transportation fuel becomes a short-term option since its production technology is fully grown and combined with gasoline. The 2nd generation ethanol still has involvement on the planet biofuels circumstance. In this study, water lettuce (Pistia stratiotes) fresh and dry biomass applied with alkalis (NaOH) and acid (H2SO4) were combined to pretreat the abundant free-floating aquatic plant water lettuce biomass. Naturally, the water lettuce accumulates food in the form of starch, suitable for bioethanol production. The results showed that the highest total sugar (11.350 ± 0.09%), reducing sugar (4.773 ± 0.15%), and ethanol (15. 385 g/L) were obtained after pretreatment of dried water lettuce with cellulase. Consequently, water lettuce was high feasible for sustainable bioethanol production.

Performance and efficiency services for the removal of hexavalent chromium from water by common macrophytes

Water contamination by hexavalent chromium(Cr) is an emerging issue. The removal of Cr(VI) using phytoremediation via different macrophytes was investigated in this study. To reduce Cr(VI) to the permissible level in irrigation water, the ability of four common macrophytes, viz. Pistia stratiotes (PS), Salvinia minima (SM), Ipomoea aquatica (IA) and Eichhornia crassipes (EC), to remove from 0.5 to 2.0 mg Cr(VI)/L was analyzed. The overall growth of PS was enhanced by 11 to 24%, SM by 36 to 53%, EC by 65 to 101% and IA by 4 to 13% by reducing Cr from 48 to 87% within 29 days of the experiment. In successive experiments, chromium uptake by SM surpassed ∼11.86-, ∼17.17- and ∼94-fold that of PS, EC and IA, respectively, after 15 days of growth in 0.35 to 1.75 mg Cr(VI)/L. The bioconcentration factor of SM surpassed that of PS, IA and EC by 0.64 to 1.73, 1.09 to 4.07 and 0.71 to 1.85 times, while PS exceeded IA and EC by1.71 to 2.35 and 1.07 to 1.11 times, respectively. SM was thus shown to offer efficient removal of Cr(VI), from a level ≅2.0 mg/L, while a suitable combination of SM and PS was efficient at ≤1.0 mg/L. Novelty It unravels the appropriate macrophytes in terms of biomass production and Cr- uptake pattern under natural condition for phytoremediation of aqueous Cr(VI) and in turn offer services to clean the environment.

Role of dominant macrophytes to treat Nambul river, the main polluter of Loktak – a dying Ramsar site in the Indo Burma hot spot (Manipur, India)

As a part of the monitoring process of the main polluting tributary of Loktak, the paper analyzed the water characteristics of the main polluted stretch of Nambul river i.e. Imphal Urban region. The results showed low pH (6.23 ± 0.32), high electrical conductivity (1373 ± 50.33 µSm−1), high turbidity (25.40 ± 0.90 NTU), poor dissolved oxygen content (0.53 ± 0.24 mgL−1), high nitrate, and phosphate concentrations (9.27 ± 0.40 and 2.05 ± 0.10 mgL−1, respectively). The Water Quality Index values indicate that Nambul river is unfit for drinking. Moreover, the Sodium Percentage, Sodium Adsorption Ratio, and Kelly’s Ratio revealed the unsuitable nature of the river for irrigation. Therefore, in order to clean the river water, lab scale microcosm experimentation was carried out to highlight the potential of the dominant macrophytes viz. Eichhornia crassipes (Mart) Solms and Pistia stratiotes (L.) as phytofilters. The results showed increased pH (7.6 ± 0.11 and 7.5 ± 0.1), higher dissolved oxygen content (5.87 ± 0.30 and 3.28 ± 0.30 mgL−1), less turbidity (0.60 ± 0.25 and 0.40 ± 0.15 NTU) and reduced nitrate and phosphate concentrations (0.37 ± 0.03 and 0.52 ± 0.01 mgL−1, and 0.534 ± 0.025 and 0.346 ± 0.01 mgL−1, respectively). Novelty statement The present study showed the deteriorating water quality of Nambul river, the main polluting source of Loktak – a Ramsar site in the Montreux records. Water Quality Index calculated was above the unsuitable level for drinking at all the sampling locations in the Imphal Urban region. Sodium percentage, sodium adsorption ratio and Kelly’s ratio were above the desired limit, making the river water unfit for irrigation. Further, the microcosm experimentation showed that the dominant macrophytes viz. Eichhornia crassipes (Mart) Solms and Pistia stratiotes (L.) can control the pollution level of Nambul.

II- from ecological recycling of Pd to greener sonogashira cross-coupling reactions

Based on a new process derived from biosorption technology that uses roots from aquatic and wetland plants (Mentha aquatica, Eichhornia crassipes, Pistia stratiotes, Ludwigia peploides, Fallopia japonica), materials rich in lignin (pinecone, bark pine) and wastes rich in tannins (coffee grounds), we were able to prepare a new class of ecocatalyst, called Eco-Pd. The formed Eco-Pd are characterized via MP-AES and XRDP in the order to elucidate the chemical composition and the structure of the new formed materials. Interestingly, the presence of higher-oxidation-state palladium species, namely K2PdCl6, is observed. We describe the use of this new generation of Eco-Pd for a green and sustainable Sonogashira reaction. The absence of copper, ligands, additives, a lower Pd loading (0.05 mol% - 0.1 mol%), the use of green solvents (glycerol/n-BuOH), and the use of biosourced Pd and base (Eco-Ca), are significant advantages of this approach. The combination TON/TOF (103/250 h−1) can be advantageously compared with literature and demonstrates the remarkable practical utility of these new catalysts. Most importantly, the Eco-Pd can be easily recycled by biosorption and reused, that is another asset in terms of sustainable Chemistry.

POME Treatment Technology Using Biological and Physical Methods: A Review

Palm oil mills have been identified as one of the main sources of environmental pollution as they generate both solid (decanter cake) and liquid [palm oil mill effluent (pome)] wastes. It is vital for the palm oil industry to implement effective measures in order to mitigate its environmental impacts. The chemical oxygen demand (COD) and the biological oxygen demand (BOD), of the effluent daily analysed by the mill laboratory are important parameters related to the intensity of the environmental impacts on the wastewater. The organic content in the effluent contributes towards the BOD and its relevance lies in the oxygen content of the water courses (usually rivers) into which the effluent is discharged. At values in excess of 100 ppm in the effluent stream, the water source will face starvation of oxygen resulting in the destruction of their marine life. POME can be treated with algae or specific aquatic plants. Past researches were carried out on the potential of Chlamydomonas incerta, Pistia stratiotes, Ipomoea aquatica, Chrysopogon zizanioides and Eichhornia crassipes in combating environmental concerns. The result shows that Eichhornia crassipes is able to reduce COD, BOD, N and P by up to 50, 90, 88 and 64 per cent respectively. Meanwhile, palm oil mill effluent (POME) can be treated by composting, a physical method using the plant E. crassipes, which was found to be the most effective biological method for POME treatment because its effectiveness in reducing contaminants was higher than other aquatic plants and microalgae. This review discusses several potential methods that are accepted and observed in other related researches and how biological methods compare with physical method for POME treatment. Keywords: Palm oil mill effluent, aquatic plants, phytoremediation, biological method, physical method.

Artificial propagation and larval breeding tests of the african sharptooth catfish, Clarias gariepinus conducted in captive conditions

The African catfish Clarias gariepinus is the second most cultured species in many African countries, including Senegal. Despite its economic importance in local aquaculture, artificial propagation of the species that would allow obtaining quality seed throughout the year has not yet been mastered adequately. This study aimed at producing C. gariepinus quality and mass supply seed to enhance local production. Three different types of incubation (Macdonald's bottle, water lettuce and wire mesh frame) were tested to identify the most efficient and accessible method for the producers at low cost and with a high hatching rate. The hatching rates obtained for the three different incubation methods were 26.9%, 10.0% and 6.3% for the Macdonald bottle (MB), wire frame (WF) and water lettuce (WL), respectively, while the corresponding survival rates were 91.6%, 70.4% and 77.8%.77.8%. The high hatching rate obtained with the MB could be due to the influence of permanent water circulation, which is absent in the other two hatching systems. The survival rates decreased 15 days after hatching and were 3.24%, 2.04% and 7.16%, respectively. The survival rates obtained three days after hatching were satisfactory, but the significant decrease at 15 days after hatching especially during the post- weaning phase seems to be due to the food quality, and unrelated to the hatching system. The daily individual growth, weight gain and body size of the larvae was significantly higher for larvae fed with natural food compared those that received artificial food. These results indicate that larvae preferred and fed the natural food which was permanently available in the rearing tanks. The artificial food deposited on the bottom of the tank changes appearance over time and may not be appreciated and efficiently consumed by the larvae, which may negatively impact their growth performance.

Evaluation of Biogas Production through Anaerobic Digestion of Aquatic Macrophytes in a Brazilian Reservoir

Aquatic macrophytes are important components of aquatic habitats. However, the overgrowth of aquatic plants can cause severe problems for the management of bodies of water. As a result, these plants must be removed and disposed of as waste. However, the usage of this biomass as a substrate in biogas plants would appear to be more beneficial. The present work deals with the anaerobic digestion (AD) of macrophytes species that cause inconvenience to power generation at hydroelectric plant in Minas Gerais - Brazil. The study examines the following macrophytes species; Salvinia molest Oxycarium cubense, Eichhornia crassipes, Pistia stratiotes and Brachiaria. The experiments were carried out as stainless steel reactor with temperature, agitation and pressure control. As pre-treatment of macrophytes was used heat treatment at 120°C and pressure of 1.6 atm. The maximum methane content was 60% during 40 days digestion time, for Brachiaria of higher lignin content. The result obtained, mainly with Brachiaria demonstrates the efficiency of pre-treatment for the lignocellulosic samples.

Combined treatment of synthetic textile effluent using mixed azo dye by phyto and phycoremediation

Phytoremediation is one of the biological approaches for remediating textile dyeing effluents. The objective of this study is the use of Pistia stratiotes, an aquatic macrophyte, which was found to degrade the maximum of 83% of mixed azo dye. A phytoreactor was designed and constructed to scale up the process of phytoremediation by P. stratiotes to treat 40 mg/l of synthetic textile effluent. Continuous flow phytoreactor fed with 40 mg/l (cycle 1) which showed maximum decolorization of 84%, COD removal was about 61%, BOD which was reduced up to 71.9%, and TDS removal was about 72% respectively. Further to remove the residual color and toxic effects of the dyes, Phycoremediation was followed for the mixed azo dyes using the microalgae Chlorella vulgaris which showed a maximum decolorization of 99% in the batch study and 74% in the scale-up study where the treated effluent was at the most minimal discharge. Phytotoxicity tests showed 80% of germination in treated effluent, and the plants in untreated wastewater had inhibited growth that indicates only 30% of germination. Such combined biological treatment techniques were put forward to be the most eco-friendly technology, which is cost-effective and attain zero discharge of the textile effluent.

A review of biofuel production from floating aquatic plants: an emerging source of bio‐renewable energy

AbstractAquatic plants have been considered as a cause for concern because they impede aquatic flora and fauna. However, biofuel production from aquatic plants is an emerging energy source. As a consequence, this paper presents a detailed review of bio‐fuel production from floating aquatic plants with their physicochemical properties. The main focus of this study is to evaluate the biofuel production potential of some major aquatic plants. This paper also presents some methods for biofuel production from aquatic plants that are feasible for future energy generation. Five major types of floating aquatic plants are analyzed in this study,viz. Azolla,water hyacinth, water fern, water lettuce, and duckweed, with their related biofuel production methodologies such as transesterification, pyrolysis, hydrolysis, and torrefaction. This paper also evaluates optimum bio‐fuel production conditions for aquatic plants and their upgradation methodologies. Conventional fuel and aquatic bio‐fuel properties are also compared in this study. Findings suggest that, depending on calorific value and viscosity,Azollaand water fern (Salvania molesta) are better aquatic plants to generate high‐quality (similar to diesel) biofuels compared with other aquatic plants. Bio‐fuel production from water fern, water lettuce, and duckweed are also comparatively less focused sources of energy. The cost associated with cleaning invasive aquatic plants from water can be turned into an investment by producing biofuel from aquatic plants using sustainable techniques. © 2021 Society of Chemical Industry and John Wiley & Sons, Ltd

Phytoremediation of synthetic textile dyes: biosorption and enzymatic degradation involved in efficient dye decolorization by Eichhornia crassipes (Mart.) Solms and Pistia stratiotes L.

The effectiveness of four aquatic floating plants: Eichhornia crassipes, Pistia stratiotes, Lemna minor, Salvinia sp., and a submerged plant Hydrilla sp. on decolorization and detoxification of five structurally different textile dyes: CI Direct Blue 201 (DB 201), Cibacron Blue FR, Cibanone Gold Yellow RK, Vat Green FFB, and Moxilon Blue GRL were studied. The E. crassipes and P. stratiotes showed complete decolorization of all the dyes tested, while Salvinia sp. (79-86%), L. minor (16-24%), and Hydrilla sp. (6-13%) were recorded as the least tolerance for all the dyes even after 14 days of incubation. Therefore, E. crassipes and P. stratiotes were selected for further studies using DB 201 as the model dye. E. crassipes and P. stratiotes showed complete decolorization of DB 201 at 48 and 84 h of incubation, respectively, and decolorization was well effective in the pH range 6-9. The crude extract of intracellular enzymes obtained from the roots of E. crassipes (46%) and P. stratiotes (20%) showed significant involvement on decolorization of DB 201, compared with the activity of crude extracellular extract and isolated endophytic bacteria and fungi (p ≤ 0.05). Further, 18 and 22% of biosorption of DB 201 dye were recorded by E. crassipes and P. stratiotes, respectively, suggesting that decolorization mechanisms of DB 201 dye by E. crassipes and P. stratiotes were based on biosorption and intracellular enzyme activities. The FTIR spectra and seed germination assay confirmed biodegradation and detoxification of DB 201 dye by E. crassipes and P. stratiotes plants along with complete color removal. Thus, present study confers the potential applicability of E. crassipes and P. stratiotes plants for textile dye removal and release to the environment without further treatment.

Cadmium, Iron and Chromium Removal from Simulated Waste Water Using Algae, Water Hyacinth and Water Lettuce

Phytoremediation involves the use of some aquatic plants for soil and water cleanup. It involves the use of hyperaccumulator plant species that remove metals from contaminated environment. In the present study, the effectiveness of Algae, Water hyacinth and Water lettuce for the removal of Cd, Fe, and Cr from simulated wastewater was tested. The three aquatic plants were grown in aqueous medium and supplemented with 1.0, 3.0 and 5.0mg/l of multi-component metal solution for 15 consecutive days. The experiment showed that the plants were able to accumulate the metals at all concentrations. The respective concentration (mg/kg) ranges of the metals (Cd, Fe & Cr) are: in Algae; 37.38-268.74, 3.10-80.80, 66.78-671.20; water hycinth: 16.59-277.20, 0.56-235.32, 3.12-1661.94; water lettuce: 38.58-208, 0.35-538, 6.05-283.84. The accumulation of metals increased significantly, with increase in the initial concentration of the solution. At all levels, the plants accumulated the metals more in the root than in the shoot, except for Fe in water hyacinth which shows effective translocation from root to shoot. The result also showed that water hyacinth was able to concentrate Cd and Cr better than Fe, while water lettuce concentrated Fe better. All the plants can be used in remediating wastewater, with water hyacinth revealing the best potentiality.

Evaluation of water lettuce, giant salvinia and water hyacinth systems in phytoremediation of domestic wastewater

AbstractThe objective of this research was to ascertain the best conditions for efficient applications of water lettuce, giant salvinia and water hyacinth in improving the quality of low strength domestic wastewater. Water quality assessment of the wastewater samples before (influent) and after treatment (effluent) with effect to retention times (6, 12 and 24 h) was analysed. The outcome of the study at 6 h retention showed that water lettuce (6.8–7.0 pH, 50.5% colour, 46.7% biochemical oxygen demand (BOD) and 37.8% chemical oxygen demand (COD)), giant salvinia (6.9–7.1 pH, 40.5% colour, 60% BOD and 43.2% COD) and water hyacinth (6.7–6.9 pH, 45.5% colour, 53% BOD and 35.1% COD) reduction values were achieved. At 12 h retention, water lettuce (6.6–7.0 pH, 57.2% colour, 77.1% BOD and 74.6% COD), giant salvinia (6.4–6.8 pH, 81.1% colour, 66.7% BOD and 72.2% COD) and water hyacinth (6.4–6.7 pH, 61.9% colour, 70% BOD and 61.1% COD) reduction values were achieved. Similarly, for 24 h retention, water lettuce (6.6–7.0 pH, 76.7% colour, 53.2% BOD and 70.3% COD), giant salvinia (6.6–7.0 pH, 91.4% colour, 74.7% BOD and 81.0% COD) and water hyacinth (6.4–6.9 pH, 74% colour, 58% BOD and 67.2% COD) reduction values were achieved. These findings indicated that the retention times of 12 and 24 h provided suitable conditions to break down the organic contaminants present in the shallow ponds.

Isolation of pathogens from leaf, root and rhizosphere water samples of aquatic weeds, Eichhornia crassipes and Pistia stratiotes present in the backwaters of YMCA canal, Alappuzha, Kerala, India

The presence of pathogenic microorganisms in backwaters is of a great concern and the unsafe water is responsible for 1.2 million deaths each year. In the present study, water samples beneath the aquatic weeds, leaf and root samples of E. crassipes and P. stratiotes were collected from YMCA canal, Alappuzha, Kerala state, India, and subjected to physicochemical and microbiological analysis. The pH of the water samples were in the range of 6.6 to 6.9, salinity was nil, electrical conductivity was 5.327 mS for Eichhornia crassipes sample and 882.2 mS for Pistia stratiotes rhizosphere water sample. Total dissolved solids (TDS) were 2.777 ppm and 448 ppm for E. crassipes and P. stratiotes respectively. Heterophilic plate count of E. crassipes is 11 x 103 and 3 x 102 CFU/ml for bacteria and fungi respectively. Similarly the rhizosphere water sample of P. stratiotes showed a bacterial count of 75 × 103 CFU/ml and the fungal count was 8 x 102 CFU/ml. Human pathogens such as Klebsiella. pneumoniae, Salmonella typhi, Enterococcus faecalis, E. coli, Vibrio cholerae, Salmonella enteritidis, Enterobacter aerogenes, Vibrio vulnificus etc. were isolated from leaf, root and rhizosphere water samples. Antibiotic sensitivity studies revealed that Klebsiella pneumoniae was resistant to antibiotics like Azithromycin, Co-Trimoxazole, Cefuroxime and Cefalexin. Most of the pathogens were resistant to Cefalexin.

Energetic Valorization of <i>Eichhornia crassipes</i> and <i>Pistia stratiotes</i> by Methane Production in an Anaerobic Co-digestion Process

<i>Eichhornia crassipes and Pistia stratiotes</i> are often used in phytoremediation of wastewater. Nevertheless, these macrophytes must be renewed after use to avoid recontamination of treated wastewater by dead plants. This study aims to produce of energy from a mixture of these two macrophyte es by anaerobic co-digestion in the presence of the activated sludge which acts as an inoculum. The study was carried out using a 4 L digesters batch under mesophilic conditions (35°C). The scenarios 3/1; 2/1 ratios between substrate and inoculum as well as control were used to evaluate the quantity biogas produced over a 25-day period. The pH, NH₄⁺, BOD₅ and COD were monitored to verify the stability of the process. The results of this study show that the pH varies from 6.39 to 7.31 while the NH₄⁺, COD and BOD₅ concentrations vary from 39.6 to 86.4 mg L⁻¹, 1965.8 to 2940.4 mgO₂ L^-1 and 1200 to 1500 mgO₂/L^-1 respectively. The varying ranges of these parameters have no effect on methanogenesis. When the two macrophytes were mixed in a 3/1 ratio, a volume of 13797 mL of biogas was produced with a methane content of 70.53%, a value within the range of a good quality of biogas.