Abstract:To evaluate the effects of water velocity and artificial substratum characteristics on the growth rate and biomass accumulation of periphyton, an artificial stream mesocosm experiment was conducted using alternative water sources collected from the Mangwall Stream (MW), the Han River (HR), and bank filtration water (BFW) from the Han River in the Republic of Korea. The measured concentrations of organic matter and inorganic nutrients in the MW were higher than in the HR and BFW. The surface of tile is relatively smooth and nonporous, whereas the surfaces of concrete and pebble are rough with numerous isolated pores in which filamentous periphyton become immobilized against hydrodynamic shear stress and mat tensile strength. Compared with the periphyton biomass of the HR and BFW, the peak biomass in the MW was significantly higher due to higher nutrient concentrations in the MW. Reasonable linear relationships (R 2 ≥ 0.69) between water velocity and total periphyton biomass/growth rate were obtained, indicating that water velocities above critical values can cause a reduction in biomass accrual. In addition, reasonable relationships (R 2 ≥ 0.58) between specific surface area and total periphyton biomass were obtained for the HR and BFW, indicating that an increase in the specific
OPEN ACCESSWater 2013, 5 1724 surface area of the substratum can lead to an increase in periphyton biomass in a nutrient-poor water body. Principal components analysis (PCA) results indicate that nutrient concentrations were the first dominant limiting factor for the growth and accumulation of periphyton, and water velocity and the specific surface area of the substratum were determined to be potential limiting factors. Consequently, the growth rate and biomass accumulation of periphyton were considered to be a complex function of nutrient concentrations, water velocities, and substratum characteristics.
Surface characteristics, physicochemical properties, functional groups, and bioactive compounds of microalgal biomass (MB) samples harvested from various wastewater treatment facilities (WTFs) were investigated to evaluate the reuse feasibility of MB as a potential renewable source of plant biostimulation. Mixtures of the microalgae cells and fine particles (i.e., silt, clay, suspended solids, extracellular organic matter, humus substances, natural organic matter, etc.) were complexed inside MB samples. MB samples harvested and air-dried under natural conditions investigated in this study can have relatively well-preserved cellular morphology as well as chemical substances such as carbohydrates, proteins, and fatty acids based on SEM-EDS analysis. A broad form of the amorphous cellulose rather than a distinct crystalline was observed from FTIR analysis, indicating that the middle spectrum of glucose and starch hydrolysate exist in MB samples. A wide array of chemicals (i.e., Undecane; Heptadecane; Hexadecanoic acid, methyl ester; and Methyl stearate, phenolics, and fatty acids) extracted from MB samples were involved in signaling plant response to abiotic stress, plant growth and biomass with MB samples were greater than those without MB samples. Thus, mixtures of nutrients, minerals and algal biomass in wet and dried MB samples can be beneficially reused as biostimulants in agricultural area after simple processes such as composting, microbial fermentation, and extraction. Further study is warranted to elucidate the effect of useful ingredients in MB harvested from on-site coagulation/flocculation processes on the soil environment as bio-fertilizers.
Commercial 28 algae removal technologies that have been applied in domestic rivers and lakes with green tide were investigated, analyzed and classified. The classification of algae removal technologies was based on the three criteria (i.e., principle, flow rate of water body, and application period). Also, algae removal technologies were evaluated in terms of cost effectiveness, field applicability, effect durability, and eco friendliness. From the analysis results, technologies using physical, chemical, biological, and convergent controls were 32.2%, 25%, 21.4%, and 21.4%, respectively. The 75% of technologies have been applied to stagnant water body (≤0.2 m/s). Also, algae harvesting ship with dissolved air flotation, conveyor belt and filtration processes and natural floating coagulant were found to have better field applicability, compared to other technologies. However, proper algae removal technology in specific rivers and lakes should be chosen after the evaluation of long-term pilot scale field test. Also, development of energy and resource recovery technologies from algae biomass is warranted.
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