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Chilli (Capsicum annuum) is an important spice crop in Bangladesh. This crop is very sensitive to waterlogging. Floating agriculture is an innovative system led by the local people of the southern region of Bangladesh, in which seedlings of vegetables are produced in low-lying areas using different aquatic macrophytes. An experiment was carried out to evaluate the viability of chilli cultivation in waterlogged areas, based on physiological and biochemical responses using floating agriculture. Eight different chilli varieties were subjected to floating agriculture in two different agronomic seasons. A soil-based chilli cultivation system was also trialled, to compare the utility of this method. To evaluate the performance of chilli in floating beds, plant water status, photosynthetic parameters, and leaf tissue concentrations of Na+, K+, NO3− and PO43−, chlorophyll, ascorbic acid and proline were assessed. This study shows that macrophytes utilised in floating beds provide favourable conditions for chilli cultivation under waterlogged conditions. Among the different varieties, Sakata 653 in summer and Jhilik in winter responded better than others. As the performance of chilli in the floating agriculture system was satisfactory in comparison with soil-based cultivation, floating agriculture can be an alternative agronomic method for chilli cultivation in waterlogged areas of Bangladesh. Floating agriculture is a promising way of crop cultivation under submergence. Production of chilli (Capsicum annuum), an important spice crop, is greatly affected by waterlogging. In submerged conditions, floating agriculture serves an alternative agronomic means of chilli cultivation. [ABSTRACT FROM AUTHOR]

Various physico-chemical methods have been employed in remediating heavy metals from wastewater, but most of them are expensive. While phytoremediation, is one cost-effective and eco-friendly technology, proves to be an alternate amongst which Vetiver, a unique tropical plant, is recognized for its large biomass and dense root system and has been proven for various remediation studies. The current research was conducted to assess the potential for Vetiver rhizofiltration of chromium. A pilot study was conducted in rhizobox wherein Vetiver was grown using sand as a medium and samples were collected from rhizobox port 1 and rhizobox port 2. Subsequently, the study was upscaled to a floating bed experiment. In both studies, Vetiver were grown under 500 mg L-1 Cr (III) solution and tannery effluent had a chromium concentration of 379 mg L-1 and the results were compared to control. Between the samples collected from port 1 and 2, the removal of chromium in port 1 was recorded to be higher than that of port 2. Moreover, the removal of chromium ions from the tannery effluent was relatively higher than the spiked solution. In both the ports, the highest removal of chromium concentration was recorded in T5 (Sand + Vetiver + Cr (III) @ 500 mg kg-1) with a removal percent of 12.59 and 10.38% in port 1 and 2, respectively. Hence, Vetiver grass has a great potential in removing pollutants like chromium from the wastewater. [ABSTRACT FROM AUTHOR]

The adverse effects of climate change, including rising sea levels and frequent floods, pose significant challenges to agricultural systems, particularly in low-lying countries like Bangladesh. To address these challenges, floating agriculture systems have emerged as a climate-resilient alternative for crop cultivation. Floating agriculture is a traditional agricultural system where aquatic free-floating macrophytes are used as the medium for the growth of plants. This cultivation system is traditionally used for seedling development in the south and south-western regions (Barishal, Pirojpur, and Gopalganj) of Bangladesh. However, very little scientific attention has been given to using macrophytes in crop production and preparing floating beds. Therefore, the present investigation has been carried out to select suitable macrophytes for preparing a floating bed by assaying the condition of the floating bed and the morphological and yield-related factors of cultivated crops during the Robi season in 2021. Five different macrophytes, namely, Salvinia molesta, Pistia stratiotes, Lemna minor, Salvinia cucullate, and Azolla pinnata , have been used as mulching material, which has been conducted in a Completely Randomized Block Design (RCBD). The plant material BARI tomato-14 has been transplanted on the floating beds to assess the effect of macrophytes on crop production. The results of the present investigation reveal that different macrophytes have distinct effects on tomato plants' growth and yield-related parameters in floating agriculture systems. Salvinia cucullata shows a better response in the stability of the floating bed, whereas Salvinia molesta exhibits better responses as mulching material on yield-related parameters of cultivated crops. • Floating agriculture is an alternative cropping system for waterlogged condition. • Macrophytes used in floating bed preparation have differential effect on tomato growth. • Salvinia molesta possess better response on tomato growth rather than other mulching materials. [ABSTRACT FROM AUTHOR]

The remediation of polluted coastal rivers is a global challenge in the environmental field. The objective of this study was to investigate the remediation feasibility of a high-salinity river using water spinach (WS) and sticky rice (SR) in hydroponic floating-bed systems. In this study, the total nitrogen (TN) removal rates were 89.7, 92.3, 85.1, and 75.2% in the WS floating-bed system and 81.2 and 78.9% in the SR floating-bed system under different salinities (2-31 psu). Additionally, the total phosphorus (TP) removal rates were 94.4, 96.4, 93.5, and 75.2% in the WS floating-bed system and 75.7 and 80.0% in the SR floating-bed system under different salinities. The results indicate that WS and SR significantly contributed to the remediation of a polluted tidal river. Additionally, increased salinity suppressed the removal of ammonium and phosphate by WS and SR. The salt tolerance of WS was greater than that of SR, which indicated that WS was a more appropriate choice for treating river contamination. [ABSTRACT FROM AUTHOR]

Previous experiences demonstrated the efficiency of the floating system for growing lisianthus (Eustoma grandiflorum L.) seedlings. Using this system, root growth usually expands through the plug cell drainage hole into the solution originating some difficulties at transplant. Pruning roots could facilitate transplant as seedlings could be taken out of the tray more easily. However, root damages at the cutting point are a possible access for pathogens. The use of Cu(OH)2 in the nutrient solution as a chemical pruning method was evaluated. Lisianthus seeds were sown in floating trays and placed in nutrient solutions containing 0, 12, 23, 46, 92 and 138 g L-1 Cu(OH)2. After 30, 40, 47 and 54 days, fresh and dry weights of seedlings were recorded. When seedlings reached four expanded leaves they were transplanted to soil in a greenhouse. At flowering, shoots were harvested to evaluate flower stem quality. Total root and shoot fresh and dry weights were higher for seedlings cultivated with 0.023 or higher doses of Cu(OH)2. However, roots mass inside the tray cell were higher in all treatments compared to the control. The use of Cu(OH)2 during plug stage improved transplant size and no effect on further plant growth and development was observed.

The planted floating bed is an innovative technology which consists of aquatic or terrestrial plants growing in a hydroponic manner with buoyant frames floating on the surface of waters. It is regarded as a low-cost, solar-energy-based and eco-friendly technology for in situ purification of surface water, and has been used all over the world as an important ecological remediation to control water eutrophication. At present, the conventional planted ecological floating bed body is generally made of natural materials and artificially synthesized materials. However, natural materials such as natural wood and bamboo are easy to rot and artificially synthesized materials such as synthetic polystyrene foam may easily cause secondary contamination if being long-term immersed in water. Porous ceramsite has high porosity and specific surface area which is in favor of absorbing microorganisms and is an ideal filtration material widely used in wastewater treatment. Biolog-ECO method has advantages over both classic cell culture techniques and molecular-level RNA (ribonucleic acid) amplification which has been widely used and shown to be a useful tool to detect differences in functional diversity of microbial populations in aquatic environments. In the present study, a novel type of floating bed carrier, which was mainly made of ceramsite functioned as a medium for biofilm growth and buoyant frames, was developed to remedy the water environment in the fishpond. Rice was planted on the floating bed functioned as nutrients assimilation species because it has strong anti-pollution and fast-growing abilities. The objective of the present study was to combine the rice hydroponic planting floating bed system and new floating bed carrier to develop an appropriate approach for the recycling of nitrogen and phosphate in the fishpond, and use it for eutrophic water remediation by studying the water quality purification efficacy and its effect on the metabolic activity and diversity of bacterioplankton in fishpond. The field experiments were carried out in 6 intensive fishponds in Jingzhou City, Hubei Province, China during the growing season in 2014. The results showed that the concentrations of total nitrogen (TN), total phosphorus (TP) and nitrite nitrogen (NO2--N) in the ponds employing the novel floating bed were significantly lower than that in the control ponds in August, and the permanganate index (IMn) was significantly lower in August and October. The metabolic pattern and diversity of bacterioplankton in the fishpond were analyzed by Biolog-ECO technique. The metabolic activity, which was indicated by average well color development (AWCD), Shannon diversity index and richness index in August and Shannon evenness diversity index in October, was significantly higher in the test ponds applying floating bed than that in the control ponds. The results indicated that the application of the novel floating bed changed the carbon source utilization pattern of the bacterioplankton communities in the intensive culture pond, and increased the metabolic activity and functional diversity of the bacterioplankton while controlled nitrogen and phosphorus nutrition level in the pond water. In addition, the rice absorbed nutrition directly from the fishpond water and formed biomass and gained a yield of 5 900 kg/hm2, which could provide extra profit. The results can provide a new approach for the regulation of water environment in aquaculture ponds, and provide valuable insight and theoretical guidance for controlling and optimizing the structure of bacterioplankton by applying the ecological engineering measures such as floating bed. [ABSTRACT FROM AUTHOR]

Floating beds were used widely for improving water quality in aquaculture environments, but its effects on ammonia changes in aquaculture environments were still not clear. In this study, the Ipomoea aquatic floating beds were introduced into 2 intensive aquaculture ponds to investigate its effect on ammonia dynamics, and 2 similar ponds set as controls. Throughout the experiment, control ponds were higher than the corresponding floating bed ponds in ammonia concentration by 6.2 ~ 75.7%, and 12.4 ~ 43.2%, respectively. The unionized ammonia concentrations of the two control ponds were 2.58 ~ 8.86-fold higher than that of the corresponding experimental ponds. In the Ipomoea aquatica fibrous roots, the amoA copy numbers of ammonia-oxidizing bacteria (AOB) ranged from (1.16 ± 0.01) x 105 to (2.33 ± 0.24) x 106 copy g-1, and those of ammonia-oxidizing archaea (AOA) ranged from (5.41 ± 0.25) x 10³ to (3.82 ± 0.37) x 104 copy g-1. The Ipomoea aquatica floating bed can efficiently remove ammonia in intensive aquaculture pond, especially can decrease the unionized ammonia level and the unionized ammonia toxicity to fish. It was assumed that the decrease of the unionized ammonia level was resulted from the pH decrease, which was contributed by the floating bed through algal photosynthesis inhibition. High richness of AOB and AOA in the Ipomoea aquatica rhizosphere indicated that the rhizospheric ammonia-oxidizing microorganisms played a vital role in ammonia removal. [ABSTRACT FROM AUTHOR]

Previous experiences demonstrated the efficiency of the floating system for growing lisianthus (Eustoma grandiflorum L.) seedlings. Using this system, root growth usually expands through the plug cell drainage hole into the solution originating some difficulties at transplant. Pruning roots could facilitate transplant as seedlings could be taken out of the tray more easily. However, root damages at the cutting point are a possible access for pathogens. The use of Cu(OH)2 in the nutrient solution as a chemical pruning method was evaluated. Lisianthus seeds were sown in floating trays and placed in nutrient solutions containing 0, 12, 23, 46, 92 and 138 g L-1 Cu(OH)2. After 30, 40, 47 and 54 days, fresh and dry weights of seedlings were recorded. When seedlings reached four expanded leaves they were transplanted to soil in a greenhouse. At flowering, shoots were harvested to evaluate flower stem quality. Total root and shoot fresh and dry weights were higher for seedlings cultivated with 0.023 or higher doses of Cu(OH)2. However, roots mass inside the tray cell were higher in all treatments compared to the control. The use of Cu(OH)2 during plug stage improved transplant size and no effect on further plant growth and development was observed. [ABSTRACT FROM AUTHOR]

Floating beds with two different eutrophic Sphagnum mosses, Sphagnum fallax and Sphagnum squarossum, were used for heavy metal removal from fluctuating degraded riverine wetlands in Songhua River. Results indicated that Sphagnum moss was adapted to water quality fluctuation in the presence of toxic Cr. The increasing quantity or blue shift of the peak position in fulvic acid-like played a promoting role in the removal of heavy metals in degraded wetland water. The accumulation of five heavy metals in Sphagnum fallax was in order of Fe > Mn > Cr > Zn > Cu, with Sphagnum fallax retaining the greatest ability to accumulate Fe up to 1780.01 ug/g. While Sphagnum squarossum retained superior potential for Mn accumulation for a long time. This study could be useful for better understanding of heavy metals restoration in fluctuating degraded riverine wetlands by eutrophic Sphagnum mosses. [ABSTRACT FROM AUTHOR]

Three floating treatment wetlands (FTWs), which consist of emergent macrophytes, were constructed and planted to investigate the influence of seasonal change on contaminant removal and harvesting strategy. The investigation was carried out by treating simulated urban stormwater runoff sewage through selected aquatic plants in Jiaxing, Yangtze River Delta, China. Samples collected from the influent and effluent water of three FTWs planted with Canna indica , Thalia dealbata , and Lythrum salicaria , respectively, were analyzed for contaminant concentration in different batches. Results demonstrated that T. dealbata outperformed C. indica and L. salicaria in nutrient removal. The FTWs of T. dealbata achieved average removal efficiencies (AREs) of 71.17% ± 2.01% for chemical oxygen demand (COD), 69.96% ± 2.11% for total nitrogen (TN), and 82.40% ± 2.34% for total phosphorus (TP) in nine stages. The COD and TN concentrations in effluent water were under 20 and 1.5 mg L −1 for 20 weeks. Based on the analyses of accumulated nutrient removal in vegetation over time, the strategy of harvesting the aboveground tissues of T. dealbata and C. indica in late October or early November is recommended. However, L. salicaria aboveground tissues should be harvested in September. In Jiaxing, the constructed FTWs of T. dealbata exhibited the best seasonal applicability. [ABSTRACT FROM AUTHOR]

A floating bed system vegetated with Oenanthe javanica was adopted in this study to treat two types of low-pollution wastewater (LPW): polluted river water (PRW) and treated domestic wastewater (DW). The water was treated for 111 days during the low-temperature season. The results indicated that the total nitrogen (TN) removal rates were higher in the DW groups than in the PRW groups during the initial 30 days. This difference may stem from the different C/N ratio of the influent. As the water temperature rose above 15.5 °C after March 12, the purification capability of nitrogen in the DW groups was enhanced, and the removal rates of TN were 89.8 and 76.8 % in DW and the control 2 at 111 days. Conversely, the performance of total phosphorus (TP) removal was robust during the initial stage of the experiment, despite receiving domestic wastewater with a relatively high N/P ratio (16:1). The TP removal rates in DW were as high as 91.5 % compared to 78.9 % in PRW at 30 days. At the same time, the N/P ratios of plant tissue were higher in the DW groups compared to that in the PRW groups. Plant uptake played a significant role in nutrient removal in the PRW groups (52.5 % for TN, 68.2 % for TP), followed by sedimentation. In contrast, plant uptake only accounted for 25.3 % of TN removal and 24.1 % of TP removal in DW. The results provide engineering parameters for the future design of an ecological remediation technology for LPW purification. [ABSTRACT FROM AUTHOR]

Nitrate (NO 3 − ) water pollution is one of the most prevailing and relevant ecological issues. For instance, the wide presence of this pollutant in the environment is dramatically altering the quality of superficial and underground waters. Therefore, we set up a floating bed vegetated with a terrestrial herbaceous species (Italian ryegrass) with the aim to remediate hydroponic solutions polluted with NO 3 − . The floating bed allowed the plants to grow and achieve an adequate development. Ryegrass was not affected by the treatments. On the contrary, plant biomass production and total nitrogen content (N-K) increased proportionally to the amount of NO 3 − applied. Regarding to the water cleaning experiments, the vegetated floating beds permitted to remove almost completely all the NO 3 − added from the hydroponic solutions with an initial concentration of 50, 100 and 150 mg L − 1 . Furthermore, the calculation of the bioconcentration factor (BCF) indicated this species as successfully applicable for the remediation of solutions polluted by NO 3 − . In conclusion, the results highlight that the combination of ryegrass and the floating bed system resulted to be effective in the remediation of aqueous solutions polluted by NO 3 − . [ABSTRACT FROM AUTHOR]

A new integrated water remediation technology, including a floating bed, a buffer zone of floating plants, enclosed 'water hyacinth' purification, economic aquatic plants and near-shore aquatic plant purification, was used in Dishui Lake to improve its water quality. A channel of 1,000 m length and 30 m width was selected to implement pilot-scale experiments both in the static period and the continuous water diversion period. The results showed that the new integrated water remediation technology exhibited the highest removal rate for permanganate index in a static period, which achieved 40.6%. The average removal rates of total nitrogen (TN), ammonia nitrogen (NH3-N) and total phosphorus (TP) in a static period were 23.2, 21.6 and 19.1%, respectively. However, it did not exhibit an excellent removal rate for pollutants in the continuous water diversion period. The average removal rates for all pollutants were below 10%. In winter, the new integrated remediation technology showed efficient effects compared to others. The average removal rate for CODMn, TN, NH3-N and TP were 7, 5.3, 7.6 and 6.5%, respectively. Based on our results, the new integrated water remediation technology was highly efficient as a purification system, especially during the static period in winter. [ABSTRACT FROM AUTHOR]

Research progresses on growth characteristics, application effect and optimization technology of I. aquatica floating bed were reviewed; its application problems in eutrophication water were discussed, and its application prospect was forecasted. [ABSTRACT FROM AUTHOR]

Abstract: To investigate the effect of the eco-remediation on nutrients and heavy metals in river water and sediment, a field study was carried out in a site of a 2-year eco-remediation mainly using planted floating bed system in an urban river in China. Before remediation, the tested properties of water and sediment in the will-be remediated area were not different from the control area, except higher concentrations of chemical oxygen demand (COD) and total nitrogen (TN) in the river water. After remediation, the remediation area showed effective removal of in-stream nutrients and elevation of dissolved oxygen and transparency. Compared to the control area, the remediation area had higher concentration of nitrate and lower concentrations of COD, ammonium, Mn and hexavalent Cr in the river water after a 2-year remediation. The remediation area also showed higher concentrations of organic carbon, TN, nitrate, sulfate, Fe, Cu, Pb and Zn in the sediment than in the control area. Accordingly, special attention should be paid to the ecological risk of heavy metals in sediments and plants in river eco-remediation projects especially in rivers polluted by heavy metals, although the metals were lower than the level of considerable ecological risk in this study. [Copyright &y& Elsevier]

Numerous studies on eutrophication remediation have mainly focused on purifying water first, then restoring submerged macrophytes. A restoration-promoting integrated floating bed (RPIFB) was designed to combine the processes of water purification and macrophyte restoration simultaneously. Two outdoor experiments were conducted to evaluate the ecological functions of the RPIFB. Trial 1 was conducted to compare the eutrophication purification among floating bed, gradual-submerging bed (GSB) and RPIFB technologies. The results illustrated that RPIFB has the best purification capacity. Removal efficiencies of RPIFB for TN, TP, NH + 4 -N, NO − 3 -N, COD Cr , Chlorophyll- a and turbidity were 74.45%, 98.31%, 74.71%, 88.81%, 71.42%, 90.17% and 85%, respectively. In trial 2, influences of depth of GSB and photic area in RPIFB on biota were investigated. When the depth of GSB decreased and the photic area of RPIFB grew, the height of Potamogeton crispus Linn. increased, but the biomass of Canna indica Linn. was reduced. The mortalities of Misgurnus anguillicaudatus and Bellamya aeruginosa in each group were all less than 7%. All results indicated that when the RPIFB was embedded into the eutrophic water, the regime shift from phytoplankton-dominated to macrophyte-dominated state could be promoted. Thus, the RPIFB is a promising remediation technology for eutrophication and submerged macrophyte restoration. [ABSTRACT FROM AUTHOR]

Four species of perennial grasses [Geophila herbacea O Kumtze (GHK), Lolium perenn CV. Caddieshack (LCC), Lolium perenne Topone (LPT) and Lolium perenne L. (LPL)] were used to remove nutrients and pollutants from refinery wastewater, of which the average concentration of total nitrogen (TN), total phosphorus (TP), chemical oxygen demand (CODMn), total petroleum hydrocarbons (TPH) were 15.6 mg L−1, 0.6 mg L−1, 142.8 mg L−1 and 1720 mg L−1, respectively. These perennial grasses had performed extremely well in removing the nutrients and pollutants and were capable of removing up to 60% of TN and 56% of TP from the refinery wastewater during 35 days treatment period, to which plant uptake contributed only 5%–10% and 10%–20%. The removal rates of CODMn and TPH were fluctuating within 52% to 67% and 40% to 55%, respectively. The nutritional value of these perennial grasses as animal feeds such as crude protein, crude fat, crude fiber, crude ash and nitrogen-free extraction after growing in refinery wastewater for 35 days were analyzed and the results suggested that these indicators were superior to national animal feed thresholds, with its nitrites and several heavy metals including zinc (Zn), arsenic (As), cadmium (Cd), and lead (Pb) concentration far below the thresholds. We concluded that perennial grass floating-bed system was effective for purifying refinery wastewater during its growing season and harvested perennial grass had great value as animal feeds. [ABSTRACT FROM PUBLISHER]

Abstract: A novel photocatalysis floating bed reactor was prepared to study for the degradation of textile wastewater. The reactor was assembled by short quartz tube loaded TiO2 film, showing a good catalytic activity. The decolorization rate of methyl orange can reach 98.7% by the photocatalysis floating bed reactor under UV light irradiation for 8hours. Scanning electron microscopy and EDS were used to characterize the structure of the photocatalyst. The results indicate that the TiO2 films of 1μm were loaded on short quartz tube in the photocatalysis floating bed reactor. [Copyright &y& Elsevier]

Abstract: The treatment capacity of an integrated constructed treatment system (CTS) was explored which was designed to reduce phosphorus (P) from secondary effluents. The integrated CTS was combined with vertical-flow constructed wetland, floating bed and sand filter. The vertical wetland was filled from the bottom to the top with gravels, steel slag and peat. Vetiver zizanioides (L.) Nash was selected to grow in the vertical constructed wetland while Coix lacrymajobi L. was grown in floating bed. The results suggested that integrated CTS displayed excellent removal efficiency for chemical oxygen demand (COD), dissolved phosphorus (DP), and total phosphorus (TP). The average COD removal efficiency of the integrated CTS was 90.45% after 40days of operation, the average DP and TP removal efficiencies of the integrated CTS were 97.43% and 96.40%, respectively. The integrated CTS has good potential in removing COD as well as P from secondary effluents. [Copyright &y& Elsevier]

The process of the two sets of deionized water units was changed from fixed bed to floating bed in the power workshop of No. 1 chemical plant in 2008. Significant economic benefits have been attained after the transformation. The defects of the unit before the transformation are analyzed, and the process principles of the floating bed, the features of the unit and the economic benefits after transformation are discussed. It provides a reference and guiding significance to other unit using fixed bed process. [ABSTRACT FROM AUTHOR]

• Pistia stratiotes has been used in design of floating bed. • Initial COD, vegetation coverage ratio and wastewater depth have been considered in designing process. • RSM based BBD model was utilized to optimize COD removal. • At the optimized conditions, highest COD removal efficiency of 96 % was obtained. Pollution of fresh water bodies is a global threat today and its the right time to take necessary steps to restore those contaminated lakes without disturbing the food web. Floating Bed (FB) is a green and sustainable technology, which can be used in treatment process. The present study aims to design a floating bed and assessing its performance for the treatment of domestic wastewater. Pistia stratiotes is considered as the plant of interest as it contains a plenty of aerenchyma tissues, which keep it in floating condition without any supporting material. Box-Behnken Design (BBD) was applied to develop the system and to study the effect of various parameters and their interaction effect on performance. The system was able to remove 96 % COD at an optimum condition : initial COD of 321.3 mg L-1, vegetation coverage ratio of 0.43 and wastewater depth of 29.4 cm. The plant also uptake significant amount of nutrient as effluents of the most experimental runs were contained below 2 mg L-1 of NH 4 +-N and 4 mg L-1 of and PO 4 3--P. A maximum Relative Growth Rate (RGR) of 0.0847 g g-1day-1 was obtained for Pistia stratiotes, when the vegetation coverage ratio was 0.25. In the kinetic analysis study, it was concluded that biodegradation followed the zero-order and first-order model with R2 value of 0.9765 and 0.9171, respectively. Overall, the system was working well and since it is one of the most eco-friendly technology, can be used in treatment of polluted water body. [ABSTRACT FROM AUTHOR]