Bioaugmentation Approaches Research Articles

Bioaugmentation to degrade the organic de-icers acetate and monopropylene glycol at low temperatures

Two de-icers, potassium acetate and monopropylene glycol (MPG), used widespread as a runway and wing de-icer respectively, can exert high BOD in the surrounding waters. A bioaugmentation approach to degrade these de-icer compounds in the drainage water prior to discharge has been tested. A microbial consortium originating from soil was enriched at low temperatures (4 degrees C) in order to adapt to wintertime conditions. With 0.05 g CDW/L of biocatalyst, maximum specific removal rates up to 1.46 and 3.33 g acetate/g CDW d at 4 degrees C were achieved with and without biostimulation respectively. An acetate:MPG mixture of 1:3 at a total COD concentration of 0.80 and 1.20 g/L was degraded in 12 days by 83 and 70% respectively. Bioaugmentation in the field over a period of 25 days showed a removal of 88% MPG compared to 46% in the control. These results demonstrate that bioaugmentation of airport runoff water can be successfully applied to prevent organic de-icer compounds from entering the receiving surface waters.

Verification of necessity for bioaugmentation—lessons from two batch case studies for bioremediation of diesel‐contaminated soils

AbstractBACKGROUND: Two bio‐pile studies undertaken in a controlled laboratory were aimed at deciding optimal strategies to remediate two different artificial diesel‐contaminated soils. Bioaugmentation with various inoculations, biostimulation with various levels of biosurfactant rhamnolipid, and nutrient enhancement were the proposed remediation courses.RESULTS: In Case I, the average of the first‐order kinetic degradation rate constants during the first degradation stage for the bioaugmentation/biostimulation treatments was 0.0195 ± 0.0056 d−1, which was about 2.6‐fold higher than that of the control batch (0.0075 d−1). Conversely, in Case II, the rate constants for treatments with amendments and those for the control batch were found to be comparable, 0.0172 ± 0.0015 d−1 and 0.0158 d−1, respectively. Microarray results indicated a less diverse indigenous bacterial community in Case I and an abundant indigenous community in Case II, both from the control batches on Day 0. The dynamics of the two microbial communities, revealed by NMS plots, emphasized the similarity among the different treatments during the first degradation stage.CONCLUSIONS: Prior to a remediation project, the usefulness of a bioaugmentation approach can be investigated using an ITS oligonucliotide microarray. Results from the microarray answered why the bioaugmentation approach was useful in Case I, but not in Case II. The abundance of the diesel‐degrading community determined the usefulness of bioaugmentation. Relatively quantified TRFLP results analyzed via the NMS plots demonstrated comparable microbial communities during the first degradation stage, regardless of differences between the two batches. The bacterial community structure might shift with the availability of hydrocarbons. Copyright © 2009 Society of Chemical Industry

Bioaugmentation of activated sludge towards 3-chloroaniline removal with a mixed bacterial population carrying a degradative plasmid

A bioaugmentation approach combining several strategies was applied to achieve degradation of 3-chloroaniline (3CA) in semicontinuous activated sludge reactors. In a first step, a 3CA-degrading Comamonas testosteroni strain carrying the degradative plasmid pNB2 was added to a biofilm reactor, and complete 3CA degradation together with spread of the plasmid within the indigenous biofilm population was achieved. A second set of reactors was then bioaugmented with either a suspension of biofilm cells removed from the carrier material or with biofilm-containing carrier material. 3CA degradation was established rapidly in all bioaugmented reactors, followed by a slow adaptation of the non-bioaugmented control reactors. In response to variations in 3CA concentration, all reactors exhibited temporary performance breakdowns. Whereas duplicates of the control reactors deviated in their behaviour, the bioaugmented reactors appeared more reproducible in their performance and population dynamics. Finally, the carrier-bioaugmented reactors showed an improved performance in the presence of high 3CA influent concentrations over the suspension-bioaugmented reactors. In contrast, degradation in one control reactor failed completely, but was rapidly established in the remaining control reactor.

Atrazine biodegradation in the lab and in the field: enzymatic activities and gene regulation

SummaryAtrazine is an herbicide of the s‐triazine family that is used primarily as a nitrogen source by degrading microorganisms. While many catabolic pathways for xenobiotics are subjected to catabolic repression by preferential carbon sources, atrazine utilization is repressed in the presence of preferential nitrogen sources. This phenomenon appears to restrict atrazine elimination in nitrogen‐fertilized soils by indigenous organisms or in bioaugmentation approaches. The mechanisms of nitrogen control have been investigated in the model strain Pseudomonas sp. ADP. Expression of atzA, atzB ad atzC, involved in the conversion of atrazine in cyanuric acid, is constitutive. The atzDEF operon, encoding the enzymes responsible for cyanuric acid mineralization, is a target for general nitrogen control. Regulation of atzDEF involves a complex interplay between the global regulatory elements of general nitrogen control and the pathway‐specific LysR‐type regulator AtzR. In addition, indirect evidence suggests that atrazine transport may also be a target for nitrogen regulation in this strain. The knowledge about regulatory mechanisms may allow the design of rational bioremediation strategies such as biostimulation using carbon sources or the use of mutant strains impaired in the assimilation of nitrogen sources for bioaugmentation.

Bioremediation of diesel oil in a co-contaminated soil by bioaugmentation with a microbial formula tailored with native strains selected for heavy metals resistance

The aim of the work is to assess the feasibility of bioremediation of a soil, containing heavy metals and spiked with diesel oil (DO), through a bioaugmentation strategy based on the use of a microbial formula tailored with selected native strains. The soil originated from the metallurgic area of Bagnoli (Naples, Italy). The formula, named ENEA-LAM, combines ten bacterial strains selected for multiple resistance to heavy metals among the native microbial community. The biodegradation process of diesel oil was assessed in biometer flasks by monitoring the following parameters: DO composition by GC-MS, CO 2 evolution rate, microbial load and composition of the community by T-RFLP, physiological profile in Biolog® ECOplates and ecotoxicity of the system. The application of this microbial formula allowed to obtain, in the presence of heavy metals, the complete degradation of n-C 12–20, the total disappearance of phenantrene, a 60% reduction of isoprenoids and an overall reduction of about 75% of the total diesel hydrocarbons in 42 days. Concurrently with the increase of metabolic activity at community level and the microbial load, the gradual abatement of the ecotoxicity was observed. The T-RFLP analysis highlighted that most of the ENEA-LAM strains survived and some minor native strains, undetectable in the soil at the beginning of the experiment, developed. Such a bioaugmentation approach allows the newly established microbial community to strike a balance between the introduced and the naturally present microorganisms. The results indicate that the use of a tailored microbial formula may efficiently facilitate and speed up the bioremediation of matrices co-contaminated with hydrocarbons and heavy metals. The study represents the first step for the scale up of the system and should be verified at a larger scale. In this view, this bioaugmentation strategy may contribute to overcome a critical bottleneck of the bioremediation technology.

Auto- and heterotrophic acidophilic bacteria enhance the bioremediation efficiency of sediments contaminated by heavy metals

This study deals with bioremediation treatments of dredged sediments contaminated by heavy metals based on the bioaugmentation of different bacterial strains. The efficiency of the following bacterial consortia was compared: (i) acidophilic chemoautotrophic, Fe/S-oxidising bacteria, (ii) acidophilic heterotrophic bacteria able to reduce Fe/Mn fraction, co-respiring oxygen and ferric iron and (iii) the chemoautotrophic and heterotrophic bacteria reported above, pooled together, as it was hypothesised that the two strains could cooperate through a mutual substrate supply. The effect of the bioremediation treatment based on the bioaugmentation of Fe/S-oxidising strains alone was similar to the one based only on Fe-reducing bacteria, and resulted in heavy-metal extraction yields typically ranging from 40% to 50%. The efficiency of the process based only upon autotrophic bacteria was limited by sulphur availability. However, when the treatment was based on the addition of Fe-reducing bacteria and the Fe/S oxidizing bacteria together, their growth rates and efficiency in mobilising heavy metals increased significantly, reaching extraction yields >90% for Cu, Cd, Hg and Zn. The additional advantage of the new bioaugmentation approach proposed here is that it is independent from the availability of sulphur. These results open new perspectives for the bioremediation technology for the removal of heavy metals from highly contaminated sediments.

Ex-situ bioremediation of polycyclic aromatic hydrocarbons in sewage sludge

Polycyclic aromatic hydrocarbons (PAH) are regarded as environmental pollutants. A promising approach to reduce PAH pollution is based on the implementation of the natural potential of some microorganisms to utilize hydrocarbons. In this study Proteiniphilum acetatigenes was used for bioaugmentation of sewage sludge to improve the PAH removal. Bioaugmentation experiments were performed in parallel semi-continuously fed reactors started up with digested primary and secondary sludge. Three bioaugmentation approaches were investigated: A1, addition of bacteria once during starting up; A2, addition of bacteria at the beginning and then every 2nd day and A3, addition of encapsulated bacteria once during starting up. Removal of PAH was found to be both biotic and abiotic. All three approaches had a positive effect of the biological removal of PAH. Highest biological removal of individual PAH (up to 80%) was observed using continuous addition (approach A2) of the bacteria to the reactors. In general, the effect of bioaugmentation was higher in the reactors fed with primary sludge compared to the reactors fed with mixed sludge. Bioaugmentation resulted in biological removal of low molecular weight PAH in the reactors fed with primary sludge using all three approaches while clear biological removal of the medium- and high molecular weight PAH only was observed if the bacteria were added continuously (approach A2).

Bioaugmentation of cyanide-degrading microorganisms in a full-scale cokes wastewater treatment facility

To enhance biological removal efficiency of total cyanides, bioaugmentation was applied to a full-scale cokes wastewaters treatment process. After a laboratorial-scale cultivation (up to 1.2 m 3) of a cyanide-degrading yeast ( Cryptococcus humicolus) and unidentified cyanide-degrading microorganisms, the microbial consortium was inoculated into a fluidized-bed type process (1280 m 3), and then enriched for two months with a huge supply of glucose, KCN and other nutrients. Target wastewater was effluent of a biological pre-denitrification process for treating cokes wastewater, and contained about 14 mg/L of total cyanides in the form of ferric cyanide. This may be a first or rare report on the full-scale bioaugmentation of specialized-microorganisms. However, continuous operation of the full-scale cyanides-degrading bioprocess showed poor removal efficiency than expected owing to poor settling performance of microbial flocs, slow biodegradation rate of ferric cyanide and lack of organic carbon sources within the wastewater. Therefore, there is a need for further studies on how to solve these operating problems in full-scale bioaugmentation approach.

Enhancing biological nitrogen removal from tannery effluent by using the efficient Brachymonas denitrificans in pilot plant operations

Laboratory scale and pilot plant reactors were inoculated with an efficient denitrifier, Brachymonas denitrificans (CCUG 45880), in order to evaluate whether a bio-augmentation approach can be used ...

Electrokinetic transport of bacteria

The remediation field is in need of a simple, safe, and cost-effective technology that directly treats contaminants sorbed to aquifer solids. In the absence of an indigenous microbial population competent to degrade the contaminants of concern, bioaugmentation, or injecting competent degradative bacteria into the subsurface has been investigated. A major problem encountered with bioaugmentation is the limited dispersion of bacteria injected into contaminated aquifers: bacteria often adhere strongly to solid surfaces. In the absence of a strong hydrogeological gradient the organisms remain localized at the origin of injection, resulting in fouling of wells and inadequate dispersion of degradative bacteria. The ability to directionally transport bacteria away from injection sites and into zones of contamination would be advantageous to bioaugmentation approaches used for in-situ remediation. Bench-scale model aquifers were used to test electrophoresis as a tool for bacterial dispersion in situ. Preliminary studies with several strains demonstrated that the net negative surface charge of bacteria in a solution at neutral pH caused electrokinetic transport of the cells through sand towards the anode in a dc electric field. Subsequent experiments were conducted in a variety of porous media with a trichloroethylene (TCE) degrading, adhesion-deficient variant of Burkholderia cepacia G4 (1CB). 1CB was directionally transported through sand, soil, and aquifer sediment at rates ranging from 1.6 to 6 cm h depending upon the porous media tested, over distances up to 0.4 m. Transport of the wild-type G4 through sand and sediment in response to a hydraulic gradient is severely retarded in relation to the adhesion-deficient 1CB, whereas electrokinetic transport rates are identical for the two strains. Experiments performed with TCE-contaminated sediment suggest that 1CB retains its ability to degrade TCE during electrokinetic transport.