Extraction of volatile fatty acids (VFAs) from water hyacinth using inexpensive contraptions, and the use of the VFAs as feed supplement in conventional biogas digesters with concomitant final disposal of water hyacinth as vermicompost

Genome of the most noxious weed water hyacinth (Eichhornia crassipes) provides insights into plant invasiveness and its translational potential

The invasive character of Eichhornia crassipes (water hyacinth) is a major threat to global biodiversity and ecosystems. To investigate the genomic basis of invasiveness, we performed the genome and transcriptome sequencing of E. crassipes and reported the genome of 1.11 Gbp size with 63,299 coding genes and N50 of 1.98 Mb. We confirmed a recent whole genome duplication event in E. crassipes that resulted in high intraspecific collinearity and significant expansion in gene families. Further, the orthologs gene clustering analysis and comparative evolutionary analysis with 14 other aquatic invasive and non-invasive angiosperm species revealed adaptive evolution in genes associated with plant-pathogen interaction, hormone signaling, abiotic stress tolerance, heavy metals sequestration, photosynthesis, and cell wall biosynthesis with highly expanded gene families, which contributes toward invasive characteristics of the water hyacinth. However, these characteristics also make water hyacinth an excellent candidate for biofuel production, phytoremediation, and other translational applications.

Ability of Indian pennywort Bacopa monnieri (L.) Pennell in the phytoremediation of sewage (greywater)

The freely and abundantly available amphibious plant Indian pennywort Bacopa monnieri (L.) Pennell was able to phytoremediate sewage (greywater) quickly and substantially in SHEFROL® ("sheet flow root level") bioreactors, achieving reductions in the levels of several indicator parameters: suspended solids, chemical oxygen demand, biological oxygen demand, nitrogen, phosphorus, zinc, copper, nickel, and manganese to the extents of about 90%, 76-77%, 80%, 65%, 55%, 56%, 42%, and 41%, respectively at hydraulic retention times of just 6 h. As these indicators of primary, secondary, and tertiary treatments were achieved simultaneously in a single reactor compartment, the system presented in this paper promises to be simple, rapid, and economical, in achieving significant treatment of greywater.

A Model to Forecast Methane Emissions from Topical and Subtropical Reservoirs on the Basis of Artificial Neural Networks

In view of the great paucity of information on the exact contributions of different causes which lead to different extents of emission of the greenhouse gas methane (CH4) form reservoirs, it is tremendously challenging to develop statistical or analytical models for forecasting such emissions. Artificial neural networks (ANNs) have the ability to discern linear or non-linear relationships despite very limited data inputs and can recognize even complex patterns in a data set without a priori understating of the underlying mechanism. Hence, we have used ANNs to develop a model linking CH4 emissions to five of the reservoir parameters about which data is most commonly available in the prior art. Using a compendium of all available data on these parameters, of which a small part was kept aside for use in model validation, it has been possible to develop a model which is able to forecast CH4 emissions with a root mean square error of 37. It indicates a precision significantly better than the ones achieved in previous reports. The model provides a means to estimate CH4 emissions from reservoirs of which age, mean depth, surface area, latitude and longitude are known.

Use of the terrestrial weed Alternanthera ficoidea in treating greywater in soil-less SHEFROL® bioreactors

The ornamental plant Alternanthera ficoidea (also named A. tenella), which is common and widespread throughout the tropics and is being increasingly regarded as an invasive, problematic weed, has been explored as a bioagent in greywater treatment. In the recently developed SHEFROL^® bioreactor, it was seen to treat greywater of varying strengths (250-1,300 mg/L chemical oxygen demand, COD) quickly and substantially to the extent of 75-77%. Biological oxygen demand (BOD), nitrogen, phosphorus, suspended solids, and heavy metals copper, nickel, manganese, and zinc were also removed to the extents of 83.5, 94.9, 33.1, 27.0, 44.8, 27.5, 38.2, and 43.2%, respectively. As all this was achieved in a single pot, single step, and in a simple reactor operation, at hydraulic retention times of a mere 6 h, it shows the process to be several times more efficient as well as potentially less expensive than the conventional treatment systems which utilize macrophytes in tanks or constructed wetlands.

Generation of highly potent organic fertilizer from pernicious aquatic weed Salvinia molesta

Utilization of Salvinia molesta, an aquatic weed which is notorious for its allelopathy and invasiveness, has been explored by its vermicomposting. Fourier transform infrared spectroscopy (FT-IR) and plant bioassay tests were conducted to analyze the composition and fertilizer value of S .molesta vermicompost. Germination and seedling growth tests were performed in soil supplemented with vermicompost at levels ranging from 0.75 to 40% by weight of the soil on three common food plants, ladies finger (Abelmoschus esculentus), cucumber (Cucumis sativus), and green gram (Vigna radiata). The influence of S. molesta's vermicompost on some of the physicochemical and biological attributes of the soil was also studied. FT-IR analysis revealed that S. molesta loses its allelopathy, as the chemical compounds that are responsible for it are largely destroyed, in the course of its vermicomposting. There is also an indication that a portion of lignin content of S. molesta is degraded. Vermicompost enhanced the germination success and promoted the morphological growth and biochemical content of the plant species studied. It also bestowed plant friendly physicochemical and biological attributes to the soil. The findings raise the prospect that billions of tons of S. molesta biomass-which not only goes to waste at present but is also a cause of serious harm to the environment-may become utilizable in organic agriculture.

The efficiency of Eichhornia crassipes in the removal of organic and inorganic pollutants from wastewater: a review

Water is a basic necessity of life, but due to overextraction and heavy input of nutrients from domestic and industrial sources, the contamination level of water bodies increase. In the last few decades, a potential interest has been aroused to treat wastewater by biological methodologies before discharge into the natural water bodies. Phytoremediation using water hyacinth is found to be an effective biological wastewater treatment method. Water hyacinth (Eichhornia crassipes), a notorious weed, being the most promising plant for removal of contaminants from wastewater is studied extensively in this regard. It has been successfully used to accumulate heavy metals, dyes, radionuclides, and other organic and inorganic contaminants from water at laboratory, pilot, and large scale. The plant materials are also being used as sorbent to separate the contaminant from water. Other than phytoremediation, the plant has been explored for various other purposes like ethanol production and generation of biogases and green manures. Such applications of this have been good support for the technocrats in controlling the growth of the plant. The present paper reviews the phytoremedial application of water hyacinth and its capability to remove contaminants in produced water and wastewater from domestic and isndustrial sources either used as a whole live plant grown in water or use of plant body parts as sorbent has been discussed.

Energy production through organic fraction of municipal solid waste-A multiple regression modeling approach

In the 21st century, people migrated from rural to urban areas for several reasons. As a result, the populations of Indian cities are increasing day by day. On one hand, the country is developing in the field of science and technology and on the other hand, it is encountering a serious problem called 'Environmental degradation'. Due to increase in population, the generation of solid waste is also increased and is being disposed in open dumps and landfills which lead to air and land pollution. This study is attempted to generate energy out of organic solid waste by the bio- fermentation process. The study was conducted for a period of 7 months at Erode, Tamilnadu and the reading on various parameters like Hydraulic retention time, organic loading rate, sludge loading rate, influent pH, effluent pH, inlet volatile acids, out let volatile fatty acids, inlet VSS/TS ratio, outlet VSS/TS ratio, influent COD, effluent COD and % of COD removal are recorded for every 10 days. The aim of the present study is to develop a model through multiple linear regression analysis with COD as dependent variable and various parameters like HRT, OLR, SLR, influent, effluent, VSS/TS ratio, influent COD, effluent COD, etc as independent variables and to analyze the impact of these parameters on COD. The results of the model developed through step-wise regression method revealed that only four parameters Influent COD, effluent COD, VSS/TS and Influent/pH were main influencers of COD removal. The parameters influent COD and VSS/TS have positive impact on COD removal and the parameters effluent COD and Influent/pH have negative impact. The parameter Influent COD has the highest order of impact, followed by effluent COD, VSS/TS and influent pH. The other parameters HRT, OLR, SLR, INLET VFA and OUTLET VFA were not significantly contributing to the removal of COD. The implementation of the process suggested through this study might bring in dual benefit to the community, viz treatment of solid waste and creation of energy.

Controlled pesticide release of a novel superabsorbent by grafting citric acid onto water hyacinth powders with the assistance of dopamine

To treat the presence of abundant water hyacinth, increase biodegradability and reduce cost of water-absorbing material, CA–PD@WH composite was fabricated by chemical modification of dopamine-coated water hyacinth with citric acid.

Management of sewage sludge by composting using fermented water hyacinth

The goal of the present research work was to assess the management of sewage sludge (SS) by composting using fermented water hyacinth (WHferm) as an amendment. The water hyacinth was fermented, and a higher production of volatile fatty acids (VFAs) (782.67 mg L(-1)) and soluble organic carbon (CSOL) (4788.34 mg L(-1)) was obtained using a particle size of 7 mm compared to 50 mm. For composting, four treatments (10 kg fresh weight each) were evaluated: treatment A (100 % SS + 0 % WHferm), treatment B (75 % SS + 25 % WHferm), treatment C (50 % SS + 50 % WHferm), and treatment D (25 % SS + 75 % WHferm). The WHferm added to SS, especially in treatments C (50 %) and D (75 %), increased the initial contents of organic matter (OM), organic carbon (CORG), CSOL, the C/N ratio, and the germination index (GI). The heavy metal content (HMC) (As, Cd, Cr, Cu, Hg, Ni, Pb, and Zn) at the beginning was below the maximum allowed by USEPA regulations. All of the samples were free of Salmonella sp. from the beginning. The reduction of the CORG, CSOL, total Kjeldahl nitrogen (TKN), and C/N ratio indicated the degradation of the OM by day 198. The treatments with WHferm (B, C, and D) yielded higher values of electrical conductivity, cation exchange capacity, and GI than SS at day 198. No significant differences were observed in GI among the treatments with WHferm. The fecal coliforms were eliminated (<3 MPN g(-1)) and the helminths were reduced to ≤5 eggs/2 g during the process. The competition for nutrients and the presence of suppressive fungi of the genera Penicillium, Rhizopus, Paecilomyces (penicillin producers), and Fusariella isolated from the compost may have promoted the elimination of pathogens since no thermophile temperatures were obtained. WHferm as an amendment in the composting of SS improved the characteristics of the final product, especially when it was used in proportions of 25 and 50 %. An excellent product was obtained in terms of HMC, and the product was B class in terms of pathogens.

A Novel Biosorbent, Water-Hyacinth, Uptaking Methylene Blue from Aqueous Solution: Kinetics and Equilibrium Studies

The adsorption of MB dye from aqueous solution onto HCl acid treated water-hyacinth (H-WH) was investigated by carried out batch sorption experiments. The effect of process parameters such as pH, adsorbent dosage, concentrations and contact time, and ionic strength were studied. Adsorption of MB onto H-WH was found highly pH dependent and ionic strength shows negative impact on MB removal. To predict the biosorption isotherms and to determine the characteristic parameters for process design, Langmuir, Freundlich, Temkin, and Halsey isotherms models were utilized to equilibrium data. The adsorption kinetics was tested for pseudo-first-order (PFO), pseudo-second-order (PSO), intraparticle diffusion (IPD), and Bangham’s kinetic models. The Langmuir isotherm model showed the goodness-of-fit among the tested models for equilibrium adsorption of MB over H-WH and indicated the maximum adsorption capacity as 63.30 mg/g. Higher coefficient of determination (R2>0.99) and better agreement between the qe (experimental) andqe(calculated) values predicted that PSO kinetic model showed the goodness-of-fit for kinetic data along with rate constant1.66×10-3,4.42×10-3, and3.57×10-3 mg·g-1min⁡-1/2⁡, respectively, for the studied concentration range. At the initial stage of adsorption, the overall rate of dye uptake was found to be dominated by external mass transfer, and afterwards, it is controlled by IPD mechanism.

Mesophilic and thermophilic anaerobic biodegradability of water hyacinth pre-treated at 80 degrees C

Water hyacinth (Eichornia crassipes) is a fast growing aquatic plant which causes environmental problems in continental water bodies. Harvesting and handling this plant becomes an issue, and focus has been put on the research of treatment alternatives. Amongst others, energy production through biomethanation has been proposed. The aim of this study was to assess the anaerobic biodegradability of water hyacinth under mesophilic and thermophilic conditions. The effect of a thermal sludge pre-treatment at 80 degrees C was also evaluated. To this end, anaerobic biodegradability tests were carried out at 35 degrees C and 55 degrees C, with raw and pre-treated water hyacinth. According to the results, the thermal pre-treatment enhanced the solubilisation of water hyacinth (i.e. increase in the soluble to total chemical oxygen demand (COD)) from 4% to 12% after 30 min. However, no significant effect was observed on the methane yields (150-190 L CH(4)/kg volatile solids). Initial methane production rates for thermophilic treatments were two fold those of mesophilic ones (6-6.5L vs. 3-3.5 L CH(4)/kg COD x day). Thus, higher methane production rates might be expected from thermophilic reactors working at short retention times. The study of longer low temperature pre-treatments or pre-treatments at elevated temperatures coupled to thermophilic reactors should be considered in the future.

Least-squares regression of adsorption equilibrium data: comparing the options

Experimental and simulated adsorption equilibrium data were analyzed by different methods of least-squares regression. The methods used were linear regression, nonlinear regression, and orthogonal distance regression. The results of the regression analysis of the experimental data showed that the different regression methods produced different estimates of the adsorption isotherm parameters, and consequently, different conclusions about the surface properties of the adsorbent and the mechanism of adsorption. A Langmuir-type simulated data set was calculated and several levels of random error were added to the data set. The results of regression analysis of the simulated data set showed that orthogonal distance regression gives the most accurate and efficient estimates of the isotherm parameters. Nonlinear regression and one form of the linearized Langmuir isotherm also gave accurate estimates, but only at low levels of random error.

Recovery of energy from Taro (Colocasia esculenta) with solid-feed anaerobic digesters (SOFADs)

We present studies on solid-feed anaerobic digesters (SOFADs) in which chopped Colocasia esculenta was fed without any other pretreatment, in an attempt to develop an efficient means of utilizing the semi-aquatic weed that is otherwise an environmental nuisance. Two types of SOFADs were studied. The first type had a single vessel with two compartments. The lower portion of the digester, 25% of the total volume, was separated from the upper by a perforated PVC disk. The weed was charged from the top and inoculated with anaerobically digested cow dung-water slurry. The fermentation of the weed in the digester led to the formation of volatile fatty acids (VFAs) plus some biogas. The bioleachate, rich in the VFAs, passed through the perforated PVC disk and was collected in the lower compartment of the digester. The other type of digesters, referred to as anaerobic multi-phase high-solids digesters (AMHDs), had the same type of compartmentalized digester unit as the first type and an additional methaniser unit. Up-flow anaerobic filters (UAFs) were used as methaniser units, which converted the bioleachate into combustible biogas consisting of approximately 60% methane. All SOFADs developed a consistent performance in terms of biogas yield within 20 weeks from the start. Among the two types of digesters studied, the AMHDs were found to perform better with a twofold increase in biogas yield compared to the first type of digesters.

Environmental challenge vis a vis opportunity: the case of water hyacinth

Water hyacinth (Eichhornia crassipes) is a noxious weed that has attracted worldwide attention due to its fast spread and congested growth, which lead to serious problems in navigation, irrigation, and power generation. On the other hand, when looked from a resource angle, it appears to be a valuable resource with several unique properties. As a result, research activity concerning control (especially biological control) and utilization (especially wastewater treatment or phytoremediation) of water hyacinth has boomed up in the last few decades. Investigations on biogas/compost production from water hyacinth have also come up very well mainly from few research groups in India. This review presents a comprehensive view of the research related to water hyacinth with special emphasis on the recent investigations on water hyacinth control and utilization technologies conducted in the last 2-3 decades. Based on these significant research achievements, now it is desirable to identify a management strategy so that the excessive growth can be controlled and the plant can be used in beneficial ways. In the rural areas, water hyacinth could be used in an integrated manner for decentralized wastewater treatment systems coupled to biogas and compost production from the resulting biomass. There is a need to work out the techno-economic viability of such integrated model systems.