A universal nutrient application strategy for the bioremediation of oil-polluted beaches

Biostimulation by nutrient application is a viable technology for restoring oil-contaminated beaches. Maximizing the nutrient residence time is key for achieving a rapid cost-effective cleanup. We considered the nutrient injection strategy through a perforated pipe at the high tide line and we simulated numerically beach hydraulics, which allowed us to estimate the optimal injection flow rate of nutrient solution. Our results indicate that the optimal application is one that starts following the falling high tide and lasts for half tidal cycle. The saturated wet-front of the nutrient solution on the beach surface would move seaward with the same speed of the falling tide keeping a constant distance with the tide line. The numerical results were generalized to beaches of wide ranges of hydraulic and tidal properties using a novel dimensionless formulation for water flow and solute transport in porous media. Nomographs were presented to provide the flow rate based on four parameters: The beach slope and hydraulic conductivity, and tidal amplitude and period.     

Bioremediation of Tannery Effluents Using a Consortium of Blue–Green Algal Species

Trivalent chromium in the form of basic chromium sulfate (BCS) is used for tanning hides/skins and is a strong pollutant of the soil and water bodies. Significant quantities of unutilized chemicals, such as sulfates, chlorides, are also discharged, contributing to high levels of total dissolved solids (TDS), biochemical oxygen demand (BOD), chemical oxygen demand (COD), etc. Though many treatment techniques are being practiced, biotechnological methods are gaining importance. Biosorption is recognized as a cost‐effective technology worldwide; one potential sorbent being blue–green algae (BGA), for treating metal‐bearing effluents. This work studies the feasibility of using a species each of Spirulina, Oscillatoria, and Synechocystis, individually and as a consortium, as sorbents to remove Cr³⁺ from a segregated stream, viz. exhaust chrome liquor (ECL) and synthetic BCS solution. The species studied were found to be effective in removing Cr³⁺ considerably at varying concentrations, besides reducing sulfates, BOD, COD, etc. The results of ECL experiments were more encouraging than those for BCS solution. The kinetic data on Cr³⁺ sorption onto algal biomass fit well into the pseudo‐second order model. The equilibrium data were analyzed using the classic Langmuir and Freundlich isotherm models, yielding good fits. The results of the experiments indicate that algal consortia could be good alternatives to the conventional treatment methods for leather and other industrial wastewaters containing chromium.     

Bioremediation and fodder potentials of two Sargassum spp. in coastal waters of Shenzhen,South China

In this study, the bioremediation potentials of two seaweeds (Sargassum hemiphyllum and S. henslowianum) against pollution in a coastal mariculture area of Shenzhen, South China, were investigated by comparing the growth, nutrient bioaccumulation capacity of plants from the seaweed bed (control site) with plants from the fish farm. Results indicated that both species are potential candidates for bioremediation in the fish farm areas in terms of their high growth rates and high bioaccumulation capacities on inorganic nutrients. Both Sargassum spp. contain high levels of crude protein (11.7–14.0%) and crude fat (2.2–2.7%), suggesting high nutritional values. The S. hemiphyllum may serve as a good aquaculture fodder with high nutritional compositions and low heavy metal contents. However, heavy metals (Cr, Pb and Cd) of S. henslowianum exceed the maximum allowable concentrations as aquatic feed, which restricts its fodder application. In general, the results of this study may contribute to the marine pollution bioremediation in the coastal areas of South China, especially in mariculture zones.     

对重金属和辐射污染的土壤和地下水的微生物修复

由重金属和辐射产生的环境污染在世界范围内产生了一系列问题.利用特殊的微生物如金属还原和耐金属细菌对环境中的金属和辐射污染进行处理具有非常好的前景.现场的生物修复的成功应用将对清除污染环境中的重金属和辐射提供潜在方法.最近的研究还关注于了解在微生物群体内重金属和辐射对微生物的作用.生物毯和生物膜是在生物修复中具有代表性的两种微生物群落的机能.金属的种类和价态变化、转移过程以及微生物代谢作用是对金属和辐射生物修复的三种重要的组成部分.结合以上三方面,可以更好的了解自然中的微生物和生物修复过程之间的关系.     

Analytical solutions for bacterial energy taxis (chemotaxis): Traveling bacterial bands

Motile bacteria may form bands that travel with a constant speed of propagation through a medium containing a dissolved substrate, to which they respond energy tactically. We generalize the analytical solution by Keller and Segel for such bands by accounting for (1) the presence of a porous medium, (2) substrate consumption described by a Monod kinetics model, and (3) an energy tactic response model derived by Rivero et al. Specifically, we determine the concentration profiles of the bacteria and the substrate. We also derive various expressions for the band velocity. The band velocity is also shown to equal the energy tactic velocity at the bacterial peak divided by tortuosity.     

Humic Substances as a Mediator for Microbially Catalyzed Metal Reduction

The potential for humic substances to serve as a terminal electron acceptor in microbial respiration and to function as an electron shuttle between Fe(III)-reducing microorganisms and insoluble Fe(III) oxides was investigated. The Fe(III)-reducing microorganism Geobacter metallireducens conserved energy to support growth from electron transport to humics as evidenced by continued oxidation of acetate to carbon dioxide after as many as nine transfers in a medium with acetate as the electron donor and soil humic acids as the electron acceptor. Growth of G. metallireducens with poorly crystalline Fe(III) oxide as the electron acceptor was greatly stimulated by the addition of as little as 100 μM of the humics analog, anthraquinone-2,6-disulfonate. Other quinones investigated, including lawsone, menadione, and anthraquinone-2-sulfonate, also stimulated Fe(III) oxide reduction. A wide phylogenetic diversity of microorganisms capable of Fe(III) reduction were also able to transfer electrons to humics. Microorganisms which can not reduce Fe(III) could not reduce humics. Humics stimulated the reduction of structural Fe(III) in clay and the crystalline Fe(III) forms, goethite and hematite. These results demonstrate that electron shuttling between Fe(III)-reducing microorganisms and Fe(III) via humics not only accelerates the microbial reduction of poorly crystalline Fe(III) oxide, but also can facilitate the reduction of Fe(III) forms that are not typically reduced by microorganisms in the absence of humics. Addition of humic substances to enhance electron shuttling between Fe(III)-reducing microorganisms and Fe(III) oxides may be a useful strategy to stimulate the remediation of soils and sediments contaminated with organic or metal pollutants.     

Biologische Aufbereitung eines BTEX-belasteten Grundwassers in einem Festbettreaktor

Biological Treatment of a BTEX-contaminated Groundwater in a Fixed-bed Reactor Conditions for the on-site operation of a fixed-bed bioreactor for remediation of contaminated groundwater were simulated and optimized in the laboratory. Two carrier materials, polypropylene rings and porous clay beads were compared. Laboratory experiments revealed that the originally planned aeration rate of 100 m³ h^–1 for the on-site-reactor (working volume 10.6 m³) had to be reduced to less than 0.7 m³ h^–1 to avoid complete stripping of BTEX-compounds and to allow biofilm formation on the carrier material. The high ground water flow rate of 5 m³ per square meter of reactor surface area and hour did not prevent biofilm formation. With a bubble-free aeration system in the fixed-bed reactor with clay beads that contained an active biofilm on the surface, 97% of benzene and 99% of the total BTEX-compounds were eliminated by respiration within one hour residence time. In the reactor with polypropylene rings, only 94% of the benzene and 83% of the total BTEX-compounds were degraded under similar conditions. Thus, for BTEX-elimination clay beads performed better in the fixed-bed reactor than the polypropylene rings.