Ecological Restoration of Wetland Polluted by Heavy Metals in Xiangtan Manganese Mine Area

Due to manganese mining and slag accumulation, the geological structure of the wetland polluted by heavy metals in Xiangtan Manganese Mine area was seriously damaged, hence biodiversity loss, severe soil, and water pollution, as well as serious heavy metal pollution to food, vegetables, and other natural sources. In order to restore the ecological environment of the mining area, in 2015, the ecological restoration test of heavy metal polluted wetlands in the mining area was carried out. The results showed that the Mn content of different parts of Koelreuteria paniculata root from high to low order: fine root > small root > medium root > large root. The Mn content of different parts of Elaeocarpus decipiens root from high to low order: large root > medium root > small root > fine root. The order of Mn content in plants of the wetland restoration from high to low is as follows: Canna warscewiezii > Thalia dealbata > Boehmeria > Pontederia cordata > Typha orientalis > Nerium oleander > Softstem bulrush > Iris germanica > Acorus calamus > Arundo donax > Phragmites australis; The order of Internal Cu content from high to low is as follows: Acorus calamus > Thalia dealbata > Softstem bulrush > Canna warscewiezii > Typha orientalis > Arundo donax > Boehmeria > Iris germanica > Pontederia cordata > Nerium oleander > Phragmites australis; Zn content from high to low order is as follows: Canna warscewiezii > Acorus calamus > Thalia dealbata > Typha orientalis > Pontederia cordata > Arundo donax > Softstem bulrush > Iris germanica > Boehmeria > Phragmites australis > Nerium oleander; Cd content from high to low order is as follows: Phragmites australis > Softstem bulrush > Thalia dealbata > Nerium oleander > Boehmeria > Canna warscewiezii > Acorus calamus > Iris germanica > Typha orientalis > Pontederia cordata > Arundo donax. The results of this study have provided a theoretical basis and decision-making reference for the evaluation of heavy metals polluted wetland restoration, protection, and reconstruction effects and the selection of ecological restoration modes.

Purification Efficiency of Eight Aquatic Plant Species in an Artificial Floating Island System in Relation to Extracellular Enzyme Activity and Microbial Community

An artificial floating island is an ecological restoration technology that aims to create sustainable ecosystems and improve biodiversity. Aquatic plants play an important role in wastewater purification. The floating island system exploits the combination of aquatic plants, microorganisms, and extracellular enzymes to purify wastewater. We investigated the purification efficiency of eight aquatic plant species (Ceratophyllum demersum, Elodea nuttallii, Eichhornia crassipes, lris pseudacorus, lris sibirica, Myriophyllum verticillatum, Thalia dealbata and Oenanthe javanica) cultured in wastewater. The relationships of plant purification capacity with extracellular enzyme activity and microbial community were analyzed to explore the crucial factors that affect the plant purification capacity and the mechanism of pollutants removal in different plant systems. Three plant species, namely Oenanthe javanica, Thalia dealbata, and lris pseudacorus, were the most effective for purification of ammonium-nitrogen (NH4+-N), total phosphate (TP), and chemical oxygen demand (COD) with maximum efficiencies of 76.09%, 85.87%, and 89.10%, respectively. Urease, alkaline phosphatase (AP), and β-glucosidase activities were significantly and positively correlated with root system development (P < 0.05). Activities of urease and AP were positively correlated with NH4+-N and TP removal, respectively. The magnitude of urease and AP activity was generally consistent with the plant’s capacity to remove NH4+-N and TP. β-Glucosidase activity and COD removal were not significantly correlated. The dominant microbial phylum in each species treatment was Proteobacteria. Alphaproteobacteria and Bacteroidia showed > 1% relative abundance and greater involvement in degradation of pollutants in the experimental system. The results provide a scientific and theoretical basis for improvement of the plant purification efficiency of artificial floating island systems.

Assessment of the Effects of Ornamental Wetland Polyculture Combinations on Urban Sewage Treatment

Previous studies have shown that wetland plants can treat wastewater in a cost-effective and sustainable way, however, the studies on the performance of ornamental wetland plant diversity in treating urban sewage were scarce. Therefore, this study was conducted to assess and select wetland polyculture combination that was effective in urban sewage treatment in subtropical areas. We formed five combinations out of six ornamental wetland plant species including Thalia dealbata, Cyperus alternifolius, Iris pseudacorus, Lythrum sastlicaria, Nymphaea tetragona, and Zantedeschia aethiopica. The growth state and removal effects of each plant combination were systematically measured and assessed. The results indicated all the combinations exhibited remarkable total nitrogen (TN), total phosphorus (TP), ammonium nitrogen (NH­4+-N), and chemical oxygen demand chromium (CODcr) removal rate of 70.75%-77.67%, 63.86%-73.71%, 69.73%-76.85%, and 57.28%-75.69%, respectively. Additionally, pH was reduced to 7.54-8.00 in the sewage. The purification effect reached the best during 30-36th day. The comprehensive assessment showed the mixture of Thalia dealbata + Cyperus alternifolius, closely followed by Thalia dealbata + Cyperus alternifolius+ Lythrum sastlicaria, was highly effective at extracting various pollutants, and both of them could be used as favorable combinations to convert eutrophication and purify municipal wastewater. Linear regression showed that TP, TP, NH­4+-N, and CODcr. were significantly related to plant biomass, indicating that plant biomass essential indicator for screening purification plants. Our study highlighted the importance of plant diversity in biological wastewater treatment, however the competition between plants was suggested to take into consideration in future studies.

Tratamento de efluente sanitário pela associação de tanque séptico e wetland construído aerado e não aerado

O objetivo deste trabalho foi avaliar o desempenho e o comportamento de um sistema de tratamento de esgoto sanitário de uma mineradora, localizada no município de Nova Lima – MG, composto por tanque séptico (TS) seguido de um wetland aerado horizontal de escoamento subsuperficial (WAHESS) e um wetland horizontal de escoamento subsuperficial (WHESS), em escala plena e o potencial de replicabilidade em outros sistemas e empresas. O sistema de tratamento de efluentes foi dimensionado para uma vazão média diária de 40 m³ dia⁻¹, cargas de DBO (Demanda bioquímica de oxigênio) de 13,5 kg dia⁻¹, de DQO (Demanda química de oxigênio) de 27,5 kg dia⁻¹, e carga de SST (Sólidos suspensos totais) de 15 kg dia⁻¹, sendo composto por dois TS de 18 m³ cada e TDH (Tempo de detenção hidráulica) de 0,5 dia, seguido de dois Wetlands construídos (WC), sendo o primeiro com TDH de 1,49 dia⁻¹ cultivado com Cyperus prolifer e o segundo com TDH de 0,64 dia⁻¹ cultivado com Thalia Dealbata, tendo a brita nº 1 como meio suporte nos wetlands. Foram avaliadas as variáveis DBO, DQO, SST, turbidez, pH e temperatura com periodicidade quinzenal, totalizando 10 amostras no período de 03/10/2019 a 18/02/2020, além dos dados de vazão. Observou-se que o sistema de WC foi essencial para o tratamento de efluentes, sendo o WAHESS o que apresentou maiores taxas de remoção dos poluentes (94% e 88% para DBO e DQO respectivamente, SST com 83% e turbidez com 94%), seguido do WHESS. O estudo permitiu concluir que o emprego de WC para o tratamento de esgoto doméstico após tratamento por TS, foi eficiente, atingindo os valores exigidos pela legislação estadual vigente para lançamento de efluentes.

Adsorption of phosphorus onto Fe-modified Thalia dealbataderived biochar

How to remove P effectively in eutrophic water is an urgent problem to be solved. In this study, a Fe-modified biochar was prepared by pyrolyzed wetland plant Thalia dealbata. The adsorption of P was investigated by using the prepared biochar (TBC-Fe) as an adsorbent. The effects of contact time, initial P concentration, temperature and initial solution pH on adsorption behavior of P on TBC-Fe were studied. The results showed that P adsorption process on TBC-Fe was controlled by internal and external diffusion of particles, due to the adsorption kinetic was better fitted by Intra-particle diffusion model. The adsorption isotherm on TBC-Fe was well performed by Langmuir model, with a maximum P adsorption capacity of 15.86 mg/g. The best adsorption performance was exhibited at 25°C with the initial pH of 10. Overall, the results indicate a promising option of utilizing Fe-modified biochar derived from wetland plants as an efficient remediation adsorbent for phosphorus in water.