Floating Bed System Research Articles

The Algicidal Potential of a Floating-Bed System against Microcystis aeruginosa in Laboratory Conditions

The Algicidal Potential of a Floating-Bed System against Microcystis aeruginosa in Laboratory Conditions

Potential of Cyperus alternifolius, Amaranthus retroflexus, Closia cristata and Bambusa vulgaris to phytoremediate emerging contaminants and phytodesalination; Insight to floating beds technology

The main aim of this study is to consider the potential of different aquatic and terrestrial plants (Cyperus alternifolius, Amaranthus retroflexus, Closia cristata and Bambusa vulgaris( for phytoremediation of pollutants and phytodesalination through floating bed system. In this study, when Cyperus alternifolius plants were exposed to atrazine) 20 mg L -1(, OPC-LD )20 mg L -1(, OPC-LD )50 mg L -1(, fluorine )3.5 mg L -1(, and 1-4 Dioxane )25 mg L -1(, in a mesocosm treatment floating bed system, the phytoremediation efficiencies were 91.28 ± 6.35%, 82.33 ± 2.51 %, 75.67 ± 3.05%, 62.28 ± 5.77% and 42.29 ± 2.27 % respectively. When Amaranthus retroflexus plants were exposed to metformin )20 and 50 mg L-1( and OCP-LD )20 and 50 mg L-1(, 63 ± 5.24 %, 58.4 ± 2.11%, 38 ± 1.73 %, and 29 ± 01 % of the pollutants were removed. In the case of Closia cristata, the most efficiency belonged to metformin with a concentration of 50 mg L-1 . The results showed that in water containing NaCl in a range of 1000 to 2000 mg L-1 , Bambusa vulgaris with an efficiency of about 32.62 ± 4.65 % is a good candidate for phytodesalination. Consequently, C. alternifolius, a fast-growing plant with a good ecological stability in polluted water, can absorb pollutants and remains healthy after the treatment period. It is a good candidate for phytoremediation in vegetated floating beds.

The biomass accumulation and nutrient storage of five plant species in an in-situ phytoremediation experiment in the Ningxia irrigation area

Phytoremediation has been widely used and is considered an environmentally friendly and efficient method for mitigating nitrogen (N) and phosphorus (P) loads. However, the technique is rarely employed in the Ningxia irrigation area, which suffers from serious N and P pollution. To investigate ways of protecting the aquatic environment in this region, we conducted in-situ experiments along an agricultural ditch in 2014 and 2015. During the pre-experiment in 2014, five single species floating-bed systems (Zizania latifolia, Oryza sativa, Ipomoea aquatica, Lactuca sativa and Typha latifolia) and one multi-species floating-bed system with three replicates were evaluated over about two months. I. aquatica performed best with respect to biomass accumulation and nutrient storage among all plant systems. Multi-species system was not superior to single species systems: 42% and 37% of the N and P storage in the multi-species system were achieved by I. aquatica. In the formal experiment during 2015, I. aquatica was tested again and performed excellently with respect to biomass production (1.06 kg/m2), N (27.58 g/m2) and P (2.34 g/m2) uptake. Thus, this study demonstrated that I. aquatica could be used to reduce N and P loads under saline and alkaline conditions in the Ningxia irrigation area.

Feasibility assessment: application of ecological floating beds for polluted tidal river remediation.

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 (2-31psu). 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.

Effect of a strengthened ecological floating bed on the purification of urban landscape water supplied with reclaimed water

A floating bed (FB) system vegetated with calamus, iris, lythrum, and Hydrocotyle vulgaris, and a strengthened FB (SFB) system with zeolite and sponge iron as fillers were simultaneously applied to purify urban landscape water in different zones. The urban landscape water, an artificial lake of approximately 326m2, was supplied with reclaimed water during a six-month experiment. Results indicated that the concentrations of nitrogen (N) and phosphorus (P) in the SFB zone (SFBZ) were significantly lower than those in the control zone (CZ) and the FB zone (FBZ) after six months of operation. The average removal efficiencies (AREs) in the SFBZ, FBZ and CZ were 89.98%, 77.39% and 56.37%, respectively, for ammonia nitrogen (NH4+-N); 92.49%, 79.55% and 47.85%, respectively, for phosphate (PO43−-P). Meanwhile, the average concentration of Chlorophyll a and the algae density in SFBZ during the experiment were 12.54μg/L and 1.31×104cells/mL, which were lower, obviously, than those in the FBZ and CZ. Moreover, the contribution rates analysis of nutrient removal exhibited that the plant absorption in the removal of N and P occupied 27.85% and 26.36%, whereas the filler adsorption occupied 7.93% and 11.93%, respectively, in the SFB. Thus, the water quality of the artificial lake was improved greatly by the SFB which hybridized fillers and FB together. Finally, it was found that the AREs of NH4+-N and PO43−-P in the SFBZ could reach 73.93% and 84.56%, approximately 1.39 and 1.41 times that of the FBZ during the winter. Therefore, the application of an SFB can keep a stable water quality in urban landscape water and avoid the lower removal rate of an FB at low-temperature. In summary, the SFB could effectively improve the water quality of urban landscape water supplied with reclaimed water even in winter.

Differences in the treatment efficiency of a cold-resistant floating bed plant receiving two types of low-pollution wastewater.

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.

Nitrate removal from polluted water by using a vegetated floating system

Nitrate (NO3−) 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 NO3−.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 NO3− applied. Regarding to the water cleaning experiments, the vegetated floating beds permitted to remove almost completely all the NO3− added from the hydroponic solutions with an initial concentration of 50, 100 and 150mgL−1. Furthermore, the calculation of the bioconcentration factor (BCF) indicated this species as successfully applicable for the remediation of solutions polluted by NO3−. 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 NO3−.

Effect of eco-remediation using planted floating bed system on nutrients and heavy metals in urban river water and sediment: A field study in China

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.

Study on Purification of Black-Odors River Water by Floating-Bed-Grown Lythrum Salicaria with Root Regulation

The potential of Lythrum salicaria with root regulation to improve black-odors water quality in Wenzhou city was evaluated using a constructed ecological floating bed system. The roots of plants were regulated by three varieties of regulating materials which had same dimension but different pore sizes. The results showed that root regulation by materials with pores on the surface could enhance the growth of plants and create a favorable rhizosphere providing a large root surface-area for biofilm development. The material of smallest pore size had the best regulating effect. The floating beds planted with Lythrum salicaria at a static state all had a promising removal potential. Compared with plants without root regulation, the regulated plants achieved higher biomass yield, removal efficiencies and uptake of N and P. The results indicated that root regulation could promote the growth of plants and elevated the nutrient removal.

Ecological Restoration by a Multistage Floating-Bed System in a Eutrophic Urban River, China

By constructing a multistage floating-bed system by combination of macrophytes, aquatic animals and aquamats ecobase for ecolgical restoration in a eutrophic urban river, the improvement of water quality and the dynamic variation of phytoplankton was investigated. The results showed that the average removal rates were 9.85%, 15.86%, 24.47% and 12.75%, respectively. phytoplankton quantity was decreased by 22.82×104ind./L and Shannon-Weiner Index was increased by 0.11 averagely, after the restoration work in the demonstration area comparing to control area. The negative correlation between Shannon-Weiner Index of phytoplankton and TN(-0.77, P<0.01) showed that multistage system might effect phytoplankton indirectly through removing nutrients from river, which indicated that the employment of ecological restoration technology of multistage floating-bed system was effective in raising the ecological recovery efficiency of polluted water bodies.

浮床空心菜对氮循环细菌数量与分布和氮素净化效果的影响

The effect of Ipomoea aquatica floating-bed on the quantity and distribution of nitrogen cycling bacteria and nitrogen removal was investigated in plastic tanks using I.aquatica as floating-bed plant.The results showed that the number of total nitrogen cycling bacteria,ammonifying bacteria,nitrosobacteria,nitrobacteria in the I.aquatica floating-bed system was significantly higher than that in the control(P0.01).No significant difference was found for the number of denitrifying bacteria between I.aquatica floating-bed system and the control(P0.05).The number of total nitrogen cycling bacteria in I.aquatica floating-bed(7×105—3×108 MPN/g) was 2 to 5 orders of magnitude higher than that in the control(3×102—5×106MPN/g).The dominant group in the I.aquatica floating-bed system was ammonifying bacteria throughout the test period(P0.01).But the dominant group in the control had changed during the test period.The dominant bacteria group in the control was ammonifying bacteria at the sixth and twelfth day of sampling(P0.05),while ammonifying bacteria and denitrifying bacteria were dominant at the nineteenth and thirty-third day of sampling(P0.05).The dominant group in the control was denitrifying bacteria at the twenty-sixth day of sampling(P0.05).The difference in the distribution of ammonifying bacteria was not significant among endo-rhizosphere,rhizoplane and water.Nitrosobacteria was mainly distributed in the endo-rhizosphere and rhizoplane.Nitrobacteria was mainly distributed in the rhizoplane and denitrifying bacteria was mainly distributed in the water.The removal rate of NH+4-N was 91.8% in the I.aquatica floating-bed system and 88.5% in the control,respectively.NH3 volatilization could be the main way of NH+4-N removal in the control.Microbial nitrification could be the main way of NH+4-N removal in the I.aquatica floating-bed system.Since I.aquatica covered only 10% of the water surface in the floating-bed system,NH+4-N removal rates in the two systems were not significantly different.The removal rate of total nitrogen was 48.2% in the I.aquatica floating-bed system and 62.1% in the control,respectively.Due to the decay of I.aquatica induced by insects after the 19th day,the removal rate of total nitrogen in the I.aquatica floating-bed system was lower than that in the control.But the interference of insects offered a possibility to have a thorough knowledge of purification mechanism of nitrogen with ecological floating-beds.Based on the correlation analysis between the number and distribution of the nitrogen cycling bacteria and the nitrogen concentration,we found that the contribution of ammonifying bacteria and nitrosobacteria in the rhizoplane is higher than that in the endo-rhizosphere and water.The contribution of nitrobacteria and denitrifying bacteria in the water is higher than that in the endo-rhizosphere and rhizoplane.Nitrogen removal is the combined effect of plant absorption,ammoniation in the rhizoplane,nitrification and denitrification in the water in the I.aquatica floating-bed system.But the main way of nitrogen removal is microbial nitrification,denitrification and NH3 volatilization in the control.The results provide sound basis for further understanding about the purification mechanism of nitrogen with ecological floating-beds.

PURIFICATION OF REFINERY WASTEWATER BY DIFFERENT PERENNIAL GRASSES GROWING IN A FLOATING BED

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.

Nutrient concentration variations during Oenanthe javanica growth and decay in the ecological floating bed system

The ecological floating bed system is a natural alternative to technical methods of wastewater treatment and involves complex processes induced by plants or microorganisms in the wastewater. This study aimed to identify nutrient concentration variations during Oenanthe javanica (Blume) DC growth and decay in the ecological floating bed system. Results showed that the third-order polynomial equation was suitable to describe pollutant concentration changes, showing that the effect of O. javanica ecological floating bed system on polluted water could be divided into the purification phase and decay phase. During the purification phase, nutrient concentrations rapidly decreased because O. javanica influenced water microbial communities and water physical parameters (i.e., dissolved oxygen, pH, and temperature), and had a direct uptake of nutrients. However, during the decay phase, nitrogen and phosphorus concentrations in the plant tissues decreased, and these lost nutrients ultimately transferred to water and led to water quality deterioration. Results also showed that the uptake and storage of O. javanica in nutrients were temporary and the plant served only as media of the nutrients removed from the water. Under these circumstances, harvesting was an appropriate intervention to improve the treatment efficiency of O. javanica ecological floating bed system.

Removal of nutrients and veterinary antibiotics from swine wastewater by a constructed macrophyte floating bed system

The potential of three varieties of Italian ryegrass ( Lolium multiflorum Lam.), Dryan, Tachimasari and Waseyutaka, to improve the water quality of swine wastewater was evaluated using a constructed macrophyte floating bed system. With respect to reductions in levels of nutrients, chemical oxygen demand (COD), and sulfonamide antimicrobials (SAs, including sulfadiazine, sulfamethazine, and sulfamethoxazole), Dryan performed better than Tachimasari and Waseyutaka. For Dryan, total N was reduced by 84.0%, total P by 90.4%, COD by 83.4% and sulfonamide antimicrobials by 91.8–99.5%. Similar results were observed for Tachimasari and Waseyutaka. The results indicated that the treatment of swine wastewater using the constructed macrophyte floating bed system was effective in the removal of nutrients and veterinary antibiotics.

Nitrogen removal from polluted river by enhanced floating bed grown canna

Floating beds of canna can remove nitrogen from polluted river water, but the removal efficiency is not very high in a short time, so some enhanced methods must be used to improve nitrogen removal efficiency by the system. Immobilized denitrifying bacteria and aeration were added into the canna floating bed. The experimental results showed that these enhancements substantially improved the nitrogen removal efficiency of the floating beds. With the enhancements, total nitrogen removal was 72.1%, ammonia nitrogen oxidation was 100%, nitrate nitrogen removal was 75.8%, nitrite nitrogen removal was 95.9%, and COD removal was 94.6% in 5 days. Without the enhancements, the canna floating bed system removed only 50.4% of the total nitrogen, 22.4% of the nitrate nitrogen, 5.3% of the nitrite nitrogen and 39.9% of the COD, respectively, in 5 days, but did accomplish 100% oxidation of the ammonia nitrogen. The experimental results provide an improved method for the treatment of polluted river water.

PANSIES: AN ALTERNATIVE CROP FOR THE TOBACCO FLOAT BED SYSTEM

A study was conducted with pansies (Viola wittrockiana) on a tobacco float bed system to determine if plugs could successfully be grown into transplants and to determine nutrient levels that wouldprovide the best transplants. Transplants were grown in a soilless media in 72-cell polystyrene float trays, floating on four different nutrient concentrations: 25, 50, 100, or 200 ppm. Length of time needed to produce regular-size transplants is reduced by half. Only 3 weeks are needed using the floating bed system, while 6 to 9 weeks are needed for the conventional method. Transplants displayed vigorous growth with normal morphology. Plant height and weight are significantly enhanced by increasing the nutrient concentration.