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With vermireactors designed on the basis of the concept of high-rate vermicomposting recently introduced by S.A. Abbasi and co-workers, it has become possible to directly vermicompost phytomass, including pernicious weeds. It has also been shown that upon vermicomposting, even toxic and allelopathic weeds get transformed into highly plant-friendly and soil-friendly organic fertilizers. Pre-existing vemireactors were not able to achieve direct vermicomposting of weeds or other plant biomass, for reasons explained in the main text. But it is necessary to ascertain whether vermireactors can be operated indefinitely with problematic weeds and whether earthworms born in such vermireactors have adequate health and reproductive ability to sustain the vermireactors interminably. Hence the present work has been undertaken to assess the performance of three successive generations of four earthworm species in terms of their ability to vermicompost the highly ligninous aquatic weed salvinia and reproduce in the vermireactors solely fed by it. It was seen that in all cases the first generation of animals, which had been born and grown to adulthood in cow-dung fed vermiculture systems, took time to adapt to the weed-feed, but did so and remained healthy. The next generation which was born and raised in salvinia-fed vermireactor was significantly more efficient in vermicomposting salvinia while the third generation was still more efficient in comparison to the second generation. The trend of third generation being superior to the second and the second being superior to the first was manifest in the production of offspring (juveniles and cocoons) as well. All-in-all the findings, covering 16 months of uninterrupted vermireactor operation, reveal that earthworms tend to get acclimated to have salvinia as their exclusive feed and the successive generations of earthworms that are born and grown in the weed-feed reactors manifest not only greater vermicomposting efficiency but also superior reproductive ability than the earthworms which had been raised on animal manure.

As reported recently by the present authors, vermicomposting by the epigeic earthworm Eisenia fetida transforms the highly ligninous and allelopathic aquatic weed salvinia (Salvinia molesta) into a benign organic fertilizer. The present study was carried out with four other earthworm species, including three epigeic species of different sizes and phytophagic habits: Eisenia andrei, Lumbricus rubillus, and Perionyx sansibaricus. One anecic species, with geophytophagous habits, was also explored for comparison: Drawida willsi. The objective was to see whether the type of salvinia transformation caused by E. fetida is a general phenomenon or whether there are significant differences in the nature of biocomposts generated by different earthworm species. Accordingly, the characteristics of the biocomposts separately generated by each of the six species mentioned above were assessed with UV-visible spectrophotometry, Fourier-transform infrared spectrometry, differential scanning calorimetry, thermogravimetry, and scanning electron microscopy. The studies reveal that, with minor variations, the biocomposting by all four species was able to remove the intransigence of salvinia and impart plant/soil-friendly attributes to it in substantial measures. All the findings obtained with different techniques corroborated each other in arriving at this conclusion. Hence, it can be said that, in general, biocomposting by earthworms takes away the toxicity of pernicious weeds such as salvinia, converting them into plant-friendly and soil-friendly biofertilizers.

A circular (close-loop) biorefinery, which integrates wastewater treatment with the generation of an energy precursor and organic fertilizer, tested at the level of a pilot plant treating 54,000 L per day (LPD) of sewage, is described. In the biorefinery’s first stage, sewage was treated in a novel SHEFROL® (sheet-flow-root-level) bioreactor at a very rapid rate, indicated by a hydraulic retention time of a mere 6 h, to a level that met the prevailing national standards for the discharge of treated sewage. The main bioagent of the reactor—water hyacinth—was then processed for the generation of energy precursors. For this, volatile fatty acids (VFA) were extracted in a simple batch reactor operating at ambient temperature and pressure. The ‘spent’ weeds were then converted into organic fertilizer, also at ambient temperature and pressure, by the high-rate vermicomposting process earlier reported by the authors. In this manner, wastewater treatment, energy production, and the generation of a fertilizer were achieved rapidly and efficiently, creating a circular close-loop system that required very little energy and materials and generated almost zero net waste.

Licorice processing industry produces a characteristic wastewater with a high chemical oxygen demand (COD), high turbidity, and intense color. Direct disposal of untreated licorice processing wastewater into water bodies can pose a serious risk to the human health and environment. The main objective of this study is to evaluate the performance of a novel laboratory scale continuous electrocoagulation (EC) reactor using iron (Fe) rod electrodes (anode and cathode) for treating a real licorice processing wastewater. Response surface methodology (RSM) was employed to investigate the effects of important parameters such as: current density (CD), electrolysis time, mixing intensity, and NaCl concentration for Fe rod electrodes on the removal efficiency of color, soluble COD (sCOD), and turbidity. In order to evaluate the effect of reactor design on the overall process performance, the results were compared with our previous study in which Fe plate electrodes were employed in an identical system. The process exhibited better performance in terms of turbidity removal for Fe rod electrodes with an average value of 59.35% in contrast to Fe plate electrodes (47.88%). Color and sCOD removal efficiencies of 94.6% and 90.1% were achieved, respectively for the EC system using Fe rod electrodes under optimum conditions: electrolysis time (71.8 min), CD (28 mA/cm2), mixing intensity (45 rpm). While in the EC reactor using Fe plate electrodes, the optimum (electrolysis time of 81.8 min, current density of 35 A/cm2, and mixing intensity of 45 rpm) color and sCOD removal were obtained 90.1% and 89.4%, respectively. Analysis and comparison of the data revealed that Fe rod electrodes delivered a better treatment performance than Fe plate electrodes, taking into account that the optimum electrolysis time and applied current density were considerably lower for the Fe rod electrodes. Overall, these results confirmed that the novel EC reactor using Fe rod electrodes can reduce the operating cost and be proposed as a pragmatic approach to remove high amount of color, COD, and suspended solids from licorice processing wastewater.