TREATMENT OF BAUXITE RESIDUE

Abstract

A method for treating bauxite residue contained in a storage facility comprising adding a mixture containing (a) a source of organic carbon, (b) a source of phosphorous or a source of phosphate, (c) a source of calcium, and a source of sulphur or sulphate to the bauxite residue, to thereby promote growth of microbes well adapted to highly saline and alkaline habitat, or to promote growth of marine microbes, or to promote growth of tolerant and marine origin haloalkaliphilic bacteria, or to promote growth of haloalkaliphilic organotrophic bacteria, preferably of marine origin. The method may comprise adding plant material or mulch and superphosphate fertilisers to the bauxite residue.

Claims

1. A method for treating bauxite residue contained in a storage facility comprising adding a mixture containing (a) a source of organic carbon, (b) a source of phosphorous or a source of phosphate and (c) a source of calcium, to the bauxite residue, wherein haloalkaliphilic bacteria are also present.

2. A method as claimed in claim 1 further comprising adding a source of S or a source of sulphate to the bauxite residue.

3. A method as claimed in claim 1: (a) the bauxite residue contains microbes well adapted to highly saline and alkaline habitat, or marine microbes, or tolerant and marine origin haloalkaliphilic bacteria or haloalkaliphilic organotrophic bacteria, preferably of marine origin, and adding the mixture promotes growth of the microbes; or (b) further comprising adding a source of microbes well adapted to highly saline and alkaline habitat, or marine microbes, or tolerant and marine origin haloalkaliphilic bacteria or haloalkaliphilic organotrophic bacteria, preferably of marine origin of microbes well adapted to highly saline and alkaline habitat, or marine microbes, to the bauxite residues.

4. (canceled)

5. (canceled)

6. A method as claimed in claim 1 wherein the mixture is applied to the bauxite residue by spreading the mixture on top of the bauxite residue in the storage facility and ploughing or otherwise mixing the mixture into the bauxite residue.

7. A method as claimed in 1 wherein the source of organic carbon comprises plant biomass residues or plant mulch: (a) having relatively high levels of total carbohydrates and an N:C ratio suitable for intensive organic acid production; or (b) having a carbon:nitrogen ratio no higher than 80:1, or from 10:1 to 60:1, or from 20:1 to 40:1.

8. (canceled)

9. A method as claimed in claim 1 wherein the method comprises adding a mixture containing green plant litter and/or green plant biomass and superphosphate fertiliser to the bauxite residue.

10. A method as claimed in 1 wherein the source of organic carbon, such as plant litter or plant mulch, is added in an amount of from 10% to 60% volume/volume of the amount of bauxite residue to be treated.

11. A method as claimed in claim 1 wherein the method comprises ploughing or tilling the mixture into the bauxite residue and irrigating the bauxite residue.

12. A method as claimed in claim 1 wherein phosphorous-rich calcium-minerals, such as superphosphate, are added to the bauxite residue and the phosphate-rich calcium-minerals are added to the bauxite residue in an amount of from 1 to 30% weight/weight ratio to the bauxite residue.

13. A method as claimed in claim 1 wherein the source of P and the source of Ca comprises phosphorous rich calcium minerals, such as superphosphate, and the phosphorus rich calcium minerals contain from 5 to 10% P, by weight (calculated on the basis of P present), and the phosphorous rich calcium minerals, such as superphosphate, has a phosphorous solubility of greater than 50%, or greater than 60%, or greater than 70%, or greater than 80%.

14. A method as claimed in claim 1 wherein the source of organic carbon, the source of phosphorous or phosphate and the source of calcium and the source of sulphur or sulphate are mixed with the bauxite residue to a depth of from about 20 cm to about 5 m, or from about 50 cm to about 2 m, or from about 50 cm to about 1.5 m, or from about 50 cm to about 1 m.

15. A method as claimed in claim 1 wherein the method comprises preparing a mixture comprising the source of organic carbon, the source of phosphorous or phosphate and the source of calcium and applying that mixture to the bauxite residue, or the source of organic carbon is applied to the bauxite residue separately to the source of phosphorous or phosphate and source of calcium, or the source of organic carbon is applied to the bauxite residue and then the source of phosphorous or phosphate and the source of calcium is applied, or the source of phosphorous or phosphate and the source of calcium is applied and the source organic carbon is subsequently applied.

16. A method as claimed in claim 1 further including the step of inoculating plant material with tolerant and marine origin haloalkaliphilic bacteria and allowing the tolerant and marine origin haloalkaliphilic bacteria to build up in the plant material to form an inoculum or composted plant mulch and subsequently adding the inoculum or composted plant mulch to the bauxite residue.

17. A method as claimed in claim 16 wherein: (a) the tolerant and marine origin haloalkaliphilic bacteria are added to plant material and the plant material allowed to sit for from 1 week to 4 weeks, or from 2 weeks to 4 weeks, or for about 2 weeks, to allow for the build-up the tolerant and marine origin haloalkaliphilic bacteria in the plant material; or (b) the inoculum or composted plant mulch containing the inoculum is added to the other organic material added to the bauxite residue, or applied separately to the bauxite residue to other components added by the method; or (c) the inoculum or composted plant mulch comprises from 0.1 to 10% volume/volume of the source of organic material or plant mulch added to the bauxite residue.

18. (canceled)

19. (canceled)

20. A method as claimed in claim 1 further including adding elemental sulphur to the bauxite residue.

21. A method as claimed in claim 20 wherein the elemental sulphur is added from 12 to 18 months after the original treatment and/or the elemental sulphur is added in an amount of from 1-10% S weight/weight of the bauxite residue, or from 100-2000 kg S/hectare.

22. A method as claimed in claim 1 wherein the step of adding a mixture containing (a) a source of organic carbon, (b) a source of phosphorous or a source of phosphate, (c) a source of calcium, and a source of sulphur or sulphate to the bauxite residue is repeated one or more times.

23. A method for treating bauxite residue contained in a storage facility comprising adding a mixture containing (a) a source of organic carbon, (b) a source of phosphorous or a source of phosphate, (c) a source of calcium, and a source of sulphur or sulphate to the bauxite residue, to thereby promote growth of microbes well adapted to highly saline and alkaline habitat, or to promote growth of marine microbes, or to promote growth of tolerant and marine origin haloalkaliphilic bacteria, or to promote growth of haloalkaliphilic organotrophic bacteria, preferably of marine origin.

24. (canceled)

25. A soil amendment for amending bauxite residue in a storage facility, the soil amendment comprising a source of phosphorous or phosphate and a source of calcium, and haloalkaliphilic organotrophic bacteria.

26. The soil amendment of claim 25, the soil amendment further comprising a source of organic carbon and a source of sulphur or sulphate.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0061] FIG. 1 shows one-dimensional ATR-FTIR spectra in the 800-2000cm-1 region of representative biofilms of the bauxite residues from the CK (dotted) and Grass+P (bold line) treatments;

[0062] FIG. 2 shows a boxplot of total nucleic acids in the biofilms from CK and Grass+P;

[0063] FIG. 3 shows a box plot of protein levels in the biofilms from CK and Grass+P;

[0064] FIG. 4 shows species richness and evenness (Shannon index) and FIG. 5 shows beta diversity using unconstrained principal coordinates analysis PcoA) based on Bray-Curtis distance of virtual communities. Relative abundance of bacterial communities was square root transformed before calculating the Bray-Curtis distance. Colours presenting different treatments with 95% confidence ellipses;

[0065] FIG. 6 shows the phylum distribution of bacterial communities in the biofilm from

[0066] the CK and Grass+P treatments.

[0067] FIG. 7 shows bauxite residues attached to biofilm in the treatment of Grass+P have lower desilicated alkaline buffering minerals (e.g., sodalite), and

[0068] FIG. 8 shows interface between bauxite residues and biofilm and their impacts on mineral liberation and associated element distribution in biofilm layers.

DESCRIPTION OF EMBODIMENTS

Example 1

[0069] A field trial using lysimeters (1×1×1 m) was established at a decommissioned Rio Tinto Aluminium bauxite residues dam (S12.20, E136.73) located in Gove Peninsula (North East Arnhem land, Northern Territory, Australia), to demonstrate the effectiveness of organic biomass and phosphate amendments in concert with marine organisms for bauxite residue dealkalization, pH neutralisation and soil formation. The bauxite residues were admixed with Rhodes grass mulch and super-phosphate fertiliser, and it is expected that marine-origin bacteria would have naturally inoculated in the amended residues due to the trial site's proximity to the coastal shore (<1 km).

[0070] After several months of field incubation under irrigated conditions, the alkaline pH condition was irreversibly neutralized to pH 8.1 in the residues amended with grass mulch and P fertilizer (containing 19% Ca, 11% S and 8.8% P, applied at 7% w/w rate), where Rhodes grass naturally emerged, but not in those without any amendment. The amended bauxite residues also exhibited formation of thick surface biofilms, which have never been reported elsewhere before. The rate and extend of pH neutralization of the grass mulch and P fertilizer amended residues were significantly higher than those amended with gypsum (containing 19% Ca and 15% S, applied at 10% w/w rate) (pH 9.3).

Methodology

[0071] Both bauxite residue and biofilm samples were collected from above field trial from the treatment, with the following treatments being applied: 1) CK (control): Bauxite residue without any amendment; and 2) Grass+P (20% v/v grass mulch and 7% w/w super-P), after 12-month of field incubation and regular irrigation. The bauxite residue used to set up this field trial was sourced from newly deposited pond 5 of RTA Gove refinery, which mainly consisted of iron (Fe) and aluminium (Al) minerals including, hematite (11.8%), quartz (9.1%), sodalite (6.8%), and boehmite (4.7%). Initial bauxite residue porewater pH was 11.7 and electrical conductivity (EC) 9.4 mS cm.sup.−1, with a high level of potential alkalinity (≈1M H+ kg.sup.−1) in the solid residue, and low levels of inorganic carbon (C) (0.4%), organic C (<0.1%), mineral nitrogen (N) (20 mg N kg.sup.−1), and inorganic phosphorous (P) (0.8 mg kg.sup.−1 water extractable P).

[0072] Naturally formed biofilms were gently scraped from the surface layer (0-1 cm) of bauxite residue across three separate areas of 10×10 cm, from the two contrasting treatments (i.e., CK and Grass+P), at least 20 cm away from any grass canopy. The bauxite residues attached to each biofilm sample were carefully removed for mineralogical, microstructural and geochemical analysis. Biofilms and bauxite residue samples were stored at approximately 4° C. in the dark during transport to the laboratory, then further sub sampled for geochemical analysis. Biofilm subsamples were frozen at −80° C. prior to DNA and protein extraction.

Results

[0073] Bauxite residue particles adhered to each of the two treatment biofilms had distinctly different geochemical characteristics. After field incubation for 12-months (including 6 month of simulated wet season using irrigation), the pH in the surface residues of the Grass+P treatment significantly decreased to 8.1 (i.e., moderately alkaline) from the initial pH 12. Bauxite residue particles attached to biofilms in the CK treatment also had a lowered pH of 10.1 after field incubation and irrigation. The strong pH neutralization in the Grass+P treatment resulted in much reduced Al solubility compared to both the CK treatment and the initial bauxite residue material.

[0074] The initial bauxite residue was extremely saline with EC of 9.4 mS cm.sup.−1 (EC1:5 water), attributable in large part to high concentrations of water-soluble Na (7405 mg kg.sup.−1). The irrigation induced leaching removal of large amounts of water-soluble Na from the surface residues in both CK and Grass+P treatments. Therefore, at the time of sampling, the bauxite residues attached to biofilms from Grass+P treatment had a much-lowered EC of 2.3 mS cm.sup.−1 and contained of 1236 mg water-soluble Na kg.sup.−1 air-dry wt. In contrast, EC and water-soluble Na of the surface residues in the CK treatment were reduced to 0.4 mS cm.sup.−1 and 658 mg kg.sup.−1, respectively. While water-soluble Na in the Grass+P residues was higher than those of the CK residues, the amount of exchangeable Na was less than half. This is consistent with the expected differences in de-alkalization effects between the two treatments. The qXRD analysis revealed that the bauxite residue from the Grass+P treatment contained 3.9% sodalite, in contrast to 7.5% in the CK and 7.8% in the original bauxite residue.

[0075] The biofilms from the CK and Grass+P treatments exhibited contrasting visual appearance in colour, thickness, and morphology. Biofilms from CK treatment showed a very smooth and moist surface with a thin, reddish layer (20-40 μm) adhering loosely to bauxite residue minerals. In the Grass+P treatment, the biofilms were greenish in colour and presented rough surfaces with many microscale bumps and protrusions, and tightly adhered to a thick layer of BR matrix. This composite layer of BR minerals and biofilms was as thick as 200-500 μm with a dense matrix profile.

[0076] The elemental mapping of biofilm-bauxite residue composites confirmed biofilm layers were enriched with Ca and P in the bacterial cells. Grass+P treatment significantly elevated the levels of available P in the bauxite residue presumably contributing to the enhanced biofilm growth and total biomass. There are induced Al/Si containing mineral in the interface between biofilm and bauxite residues, which is consistent with the elevated conductivity and reduced sodalite in treatment of Grass+P with better growth of biofilm.

[0077] The FTIR spectra of the EPS extracted from representative biofilms confirmed differences in EPS chemical composition between CK and Grass+P treatments (see FIGS. 1 to 3). Wide and intensive peaks in the region of 980-1200 cm-1 (vibrational stretching of O—H and C—O, the two most common functional groups in carbohydrates) was strongest for CK treatment EPS, whilst peaks at 1640 cm-1 and 1540 cm-1 (vibrations of the —CONH— group of Amide I and Amide II in proteins) were strongest for the Grass+P treatment EPS. A weaker peak at 1250 cm-1 (deformation vibration of C—O from carboxyl groups and stretching vibration of P—O groups) was also observed for the Grass+P treatment EPS. This suggests that the EPS of Grass+P biofilms were relatively enriched in N-containing organic compounds. Reinforcing this analysis, DNA and protein extractions found that the Grass+P biofilms were more abundant in these dominant N-containing biomolecules.

[0078] Phylogenetic profiling of bacterial communities in the biofilms revealed a total of 161,626 high quality sequences. Rarefaction analysis indicated that the sequencing depth well captured the diversity of the bacterial communities present in all biofilms. Between a relatively high levels of diversity of bacterial communities, ranging from 196 and 312 OTUs were detected across samples, without significant difference in the richness of OTU numbers or Shannon index between the CK and Grass+P treatments. Bacterial community composition differed significantly between the CK and Grass+P treatment biofilms, but both were dominated by a mixed of autotrophic bacteria (Cyanobacteria) and heterotrophic bacteria (Bacteroidetes, and heterotrophic Proteobacteria such as Rhizobacter and Sphingomonas spp.). Genus-level community compositions and the intimacy of ecological interactions also varied between CK and Grass+P biofilms. Co-occurrence network analysis revealed distinct clusters reflecting the unique community structures and ecological interactions between CK and Grass+P treatments. For example, many of the most abundant co-occurring OTUs in CK the biofilm community formed a highly condensed cluster, dominated by Flexibacter spp. (15.6%, best match with Flexibacter flexilis, organoheterotroph mainly from marine environment), Chloroflexi bacterium OLB13 (9.6%, uncultured anammox nitrite-oxidizing bacteria), and Nostoc spp. (5.5%, best match with Nostoc sp. AT703, cyanobacteria forms biocrust in hot and drylands with capability to fix atmosphere carbon and nitrogen). Bacteria in biofilm from CK treatment have abundant marine source organoheterotrophic genera, which forms highly clustered microbial module. Marine source organoheterotrophic OTUs (e.g., Pseudofulvirnonas spp., 5.2%) were also more abundant in the biofilms from treatment of Grass+P, as well as plant-root associated Proteobacteria (e.g., Rhizobacter spp. 3.4%) compared to those in CK treatment. The gene resource with application potential to survive and drive organic matter metabolisms has been summarized in Table 2. FIGS. 4 to 6 show the relevant results.

Discussion

[0079] Abundant and vigorous microbial biofilms were induced by grass mulch and phosphorus addition. The biofilms are clearly responsive to the combined amendments of grass mulch and P fertiliser under irrigated (simulating tropical wet season) and tropical climatic conditions. Vigorous biofilm establishment is highly correlated with improved soil-like conditions in the bauxite residues, and natural colonization by pioneer plant species occurred in less than 2 years under field conditions.

[0080] Microbial community beta-diversity, cell growth, and EPS production were substantially increased by the inputs of organic biomass (e.g., grass mulch rich in carbohydrates and some N) and macronutrients (particularly P). The observed high bacterial biodiversity was reflected in the diverse physiological functions represented by the Grass+P biofilm proteome. As revealed by network and proteomics analyses, Cyanobacteria were the key component in the bacterial network, active as the primary producer capable of photosynthesis and TCA carbon fixation pathway. Many are and also capable of fixing atmospheric N.sub.2 (e.g., in heterocyst) to drive biomass production. Therefore, they may competitively colonise N-limiting ecosystems, such as the N-deficient bauxite residue. However, the inputs of grass mulch and P fertilizer likely also contributed to the growth of Cyanobacteria in the Grass+P treatment, by elevating the supply of carbohydrates, organic N and available P. It is known that P deficiency limits the growth and functions of filamentous Cyanobacteria (e.g., Leptolynbgya spp. Nostoc spp.,), and many species have the ability to incorporate C and N from extracellular organic compounds.

[0081] The amended Grass+P bauxite residue also provided other organoheterotrophs with increased substrate supply, both directly from the grass mulch and super-phosphate, and possibly indirectly, through symbiotic species interactions. The SE-SEM and FISH examination revealed that bacteria other than cyanobacteria (with smaller cell sizes, without green florescence) tended to aggregate around or attach to the walls of the filamentous cyanobacteria in the bauxite residue biofilms. In this partnered system, cyanobacterial carbon overflow could become substrates to be rapidly utilized by symbiotic organoheterotrophs in the biofilms. This commensalism between cyanobacteria and organoheterotrophs may have sustained the biofilm community as a “self-carbon-sufficient” system in the amended bauxite residue in the present case.

[0082] The EPS in the biofilms of Grass+P treatment was enriched with N-containing molecules and Ca and P derived from the added super-P. Moreover, in these biofilms, proteins participating in cell growth pathways were more diverse, than those of the CK. The Grass+P treatment stimulated the growth of organoheterotrophic soil-source Proteobacteria (e.g., Rhizobacter spp., Pseudofulvimonas spp.) and aerobic Bacteroidetes (e.g., Rhodocytophaga spp.,). Overall, the biofilms in the Grass+P amended bauxite residues showed an elevated metabolic capacity to decompose complex organic compounds, compared to the CK treatment. For instance, Bacteroidetes (known as degraders of complex biopolymers) were relatively more abundant in the biofilms of Grass+P treatment, and produced a more of types of proteins. Proteins associated with other presumed organoheterotrophs (e.g., Actinobacteria and Proteobacteria) in the Grass+P biofilms were also more diverse than those of the CK treatment. In addition, biofilms of the Grass+P treatment hosted a higher number of proteins involved in N metabolisms (e.g., Polynucleotide phosphorylase, Glutamine synthetase, Agmatinase, Glycine cleavage), P metabolism (e.g., Alkaline phosphatase), and respiration (e.g., 6-phosphogluconate dehydrogenase), than the control. These results suggest grass mulch and P-fertiliser amendment stimulates an improved functional capacity for complex carbohydrate decomposition and production of organic by-products such as organic acids. Organic acid production should then lead to complexation of Al—Si minerals and rapid de-alkalization of sodalities (i.e., the solid phase alkalinity) in the bauxite residues, and neutralisation of soluble alkali in porewater.

[0083] The multi-species cyanobacteria-organoheterotrophs in the biofilms may provide a sustainable mechanism for continuous supply of organic metabolites with functional ligands of high affinity towards Al—Si minerals. This organic ligand complexation with the Al—Si cage of alkaline minerals such as sodalite is a critical process to facilitate the hydrolysis of the alkali (Na.sup.+). In the present study, the alkaline and saline tolerant biofilms boosted by Grass+P inputs significantly stimulated the weathering of minerals in the bauxite residues, as indicated by the drastically elevated levels of soluble Na, K, Ca, and Mg compared with the control (Table 1). Among the prominent bauxite residue minerals attached to the biofilms, Fe/Ti-containing minerals (e.g., hematite, rutile, anatase) appeared stable, but not Al/Si/Na containing minerals (e.g., sodalites) and Ca-rich P fertiliser minerals (i.e., super-P). In particular, Grass+P treatment lowered the relative abundance of sodalites by 50%, with much reduced exchangeable Na in resultant mineral phase, compared to those in the CK without inputs (Table 1). Simultaneously, the pH in the CK treatment remained stable after 24 months incubation, while the pH in the Grass+P treatment dropped from 9.05 to 6.10 by the end of 24 months field incubation. Therefore, this treatment eliminated the resurgence of persistent solid-phase alkalinity in the bauxite residues, resulting in pH neutralization and allowing leaching removal of excess Na in porewater under intensive rainfalls and/or field irrigations. Most excitingly, the demonstrated biofilm response and associated microbial de-alkalization are so easily stimulated by local grass mulch and a common crop fertiliser superphosphate. The resultant engineered soil in the Grass+P treatment supported natural colonization of pioneer plant species (Rhodes grass) which completed full life cycle within 2 years under field conditions.

TABLE-US-00001 TABLE 1 comparison of selected geochemistry or residue biofilms set for the treatment of CK and Grass + P and the relationship with bacterial communities as revealed by Mantel test. Mantel- Mantel- Treat- Treat- Carol Carol ment .sup.a ment T-test.sup.b test.sup.c test.sup.c Parameter CK Grass + P p-value r p pH(.sub.1:5 water), 10.13 8.06 0.001*** 0.975 0.0222* Electrical 0.4 2.3 0.011* 0.978 0.0097** conductivity (mS/cm) NO.sub.3—N (mg/kg) 2.6 9.3 0.252 0.480 0.3083 NH.sub.4—N (mg/kg) 11.2 17.3 0.620 0.339 0.5753 Available P 7.2 273.2 0.007** 0.983 0.024* (mg/kg) Water soluble anions (mg/kg) Fluoride 27.6 36.8 0.505 0.157 0.7986 Chloride 49.7 16.0 0.044* 0.832 0.0528 Sulfate 30.2 670.0 0.186 0.557 0.2403 Water extractable elements (mg/kg) Na 658.4 1235.7 0.032* 0.896 0.0375* K 1.4 6.4 0.055 0.921 0.0181** Ca 12.9 2313.0 0.017* 0.953 0.0431* Mg 3.7 66.3 0.023* 0.938 0.0264* Al 36.7 2.7 0.123 0.585 0.2847 Fe 0.22 0.11 0.072 0.668 0.1986 Exchangeable cations (mg/kg) Na 5416.4 2498.2 0.047* 0.768 0.1194 K 49.1 54.5 0.528 0.709 0.2056 Ca 2659.7 2654.9 0.970 0.680 0.1833 Mg 82.8 70.6 0.562 0.138 0.7750 CEC (cmol/kg).sup.d 37.6 24.8 0.045* 0.766 0.1097 ESP (%).sup.e 65.5 47.2 0.007** 0.883 0.0778 .sup.a Values are means for chemical properties of bauxite residues from each treatment (n = 3) .sup.bChemical properties of bauxite residues varied significantly between CK and Grass + P treatments were labelled in bold ***, **, * means P < 0.001, P < 0.01 and P < 0.05, respectively; .sup.cChemical properties posing significant impacts on the bacterial communities in the bauxite residues were labelled in bold, ***, **, * means P < 0.001, P < 0.01 and P < 0.05, respectively using Monte Carol test with 999 permutations; .sup.dcation exchange capacity .sup.eexchange sodium percentage

Example 2

[0084] Bioneutralization of alkaline bauxite residues could be achieved through in situ organic acid production from anaerobic decomposition of carbohydrates-rich organic matters (e.g., plant biomass residues) under saline and alkaline conditions. However, the efficacy and sustainability of bioneutralization in bauxite residues are limited by non-resilient growth and functions of fermentative organoheterotrophic bacteria under the extremely alkaline and saline conditions. This example investigated if by pre-composting carbohydrate-rich plant residues with soil bacteria could enhance the resilience of fermentative bacteria and associated bioneutralization efficacy in strongly alkaline bauxite residues. In this regard, some tolerant bacteria of marine origin are present in soil, but in very minor quantities and largely not effective, until they are enriched and provided the alkaline and saline conditions to activate them. In a 2-week microcosm experiment with bauxite residues (pH˜10.5), it was found that the resilience of functional bacterial groups and bioneutralization efficacy were significantly boosted in plant residues (i.e., SM: sugarcane mulch, LH: Lucerne hay) pre-composted with soil bacteria inoculum. Pre-compositing plant residues with soil microbial inoculum not only recovered 10-20% of the soil bacterial features initially inoculated, but most importantly amplified a highly diverse microbial consortium (feature richness 220-321, dominated by bacteria) in the plant residues. Remediation with precomposted plant residues resulted in pH reduction of 0.8-2.0 units, despite countering effects caused by the alkalinity buffering capacity of alkaline minerals in bauxite residues amended with the pre-composted plant residues. In contrast, the growth medium-based soil bacterial inoculation resulted in pH reduction by only 0.2-0.7 unit in the bauxite residues, with the loss of >99% of the diverse prokaryotic features of the original soil inoculum. As a result, plant residues composted with soil bacteria would be a preferred method to remediate bauxite residues for effective bioneutralization.

[0085] In the present specification and claims (if any), the word ‘comprising’ and its derivatives including ‘comprises’ and ‘comprise’ include each of the stated integers but does not exclude the inclusion of one or more further integers.

[0086] Reference throughout this specification to ‘one embodiment’ or ‘an embodiment’ means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, the appearance of the phrases ‘in one embodiment’ or ‘in an embodiment’ in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more combinations.

[0087] In compliance with the statute, the invention has been described in language more or less specific to structural or methodical features. It is to be understood that the invention is not limited to specific features shown or described since the means herein described comprises preferred forms of putting the invention into effect. The invention is, therefore, claimed in any of its forms or modifications within the proper scope of the appended claims (if any) appropriately interpreted by those skilled in the art.

TABLE-US-00002 TABLE 2 List of genome resources of functional bacteria in bauxite residues (sourced from both bauxite residues and seawater neutralized bauxite residues) Tolerant Potential metabolic Habitat Phyla Families Closest genus Features capacity pathways distribution Actinobacteria Cellulomonadaceae Actinotalea sp. Heterotrophic, NaCl: Cellulose sludge biofilm Aerobic, 0-4 fermentation reactor Non-motile pH: iron mine, 6-8 rhizobium of halophytes in desert saline soil Actinomycetospora Heterotrophic, NaCl: Cellulose saline soil, sp. Aerobic, 1-15% fermentation tropical Filamentous motile pH rainforest 6.0-10.5 Nordiopsaceae Nocardioides sp. Mesophilic, NaCl: Carbohydrate soil including Heterotrophic, 0-5% decomposer supersaline Motile pH soil, biomass 7.0-9.0 waste; (up to 12.0) waste water, saline lake Promicromonosporaceae Xylanimicrobium Heterotrophic, pH Acid producer from Decay plant sp. Non-motile, 7.0-7.5 carbohydrate tissue Anaerobic fermentation, Xylan hydrolization Propionibacterium Slow growing, NaCl: Heterofermentative Soil sp. Aerotolerant 0-6.5% synthesize propionic Plants pH acid 5.1-8.5 Streptomycetaceae Streptomyces sp. Saprotrophic NaCl: Producer a variety of Soil, 0-3% secondary metabolites Waste water pH (antibiotics, enzymes) 5.0-9.0 for extracellular functions Nitriliruptoraceae Nitriliruptor sp. Haloalkaliphilic NaCl: Nitrile (important Soda lake 0.4-8% intermediates for sediment pH synthesis organic 8.4-10.6 compounds) degradation through nitrile hydratase and amidase pathways Bacteroidetes Cytophagaceae Algoriphagus sp. Heterotrophic, NaCl: positive for oxidase, Seawater, Non-motile, 0-6% catalase and b- Marine Aerobic, pH galactosidase activity, sediment, Saccharolytic 5.5-9.5 and utilization Mud core, of D-glucose and Saline lake lactose with organic cyanobacterial acid production mats capacity Cytophaga sp. Heterotrophic, NaCl: Cellulose decomposer Soil, Anaerobic 0-6% Decay plant pH 5-9 tissue Flavobacteriia Flavobacterium sp. Heterotrophic, NaCl: Cellulose Soil Non-motile, 0-5% decomposer, Marine Aerobic pH Acid produced sediment 6.5-8.5 aerobically from carbohydrates Salegentibacter sp. Heterotrophic, NaCl: hydrolysis of cellulose Ocean Motile, 0-8% urea and chitin; Aerobic (up to 18%) acid production; pH 5-10 utilization of inositol, mannitol, sorbitol, malonate and citrate; and production of indole and acetoin Cyanobacteria Nostocaceae Nostoc sp. Photoautotrophs, NaCl: Photosynthesis, Light exposure Anabaena sp. Heterocystous, 0.2-5% produce extracellular Nutrient-poor Motile, (up to 18%) polymer substrates, soil, pH: 5-10 Nitrogen fixation Rock surface Aquatic habitat (sea, freshwater) Pseudanabaenaceae Leptolyngya sp. Photoautotrophs, NaCl: Photosynthesis, Light exposure Motile with long 0.2-3% produce extracellular saline soil, filaments, pH: 4-11 polymer substrates Rock surface Non-heterocystous Aquatic habitat (sea, freshwater) Oscillatorium Phormidium sp. Photoautotrophs, NaCl: Photosynthesis, Soil, Motile with long 0.2-5% produce extracellular Pool sediment, filaments, (up to 15%) polymer substrates Soda lake, Non-heterocystous pH: 5-11 Marine, sediments Firmicutes Bacillaceae Bacillus sp. Heterotrophic NaCl: Highest capacity to Soda lake 0.2-8% degrade hydrocarbon, (up to 15%) Alkane pH: biodegradation and 8.5-11.5 fermentation Enterococcacea Enterococcus sp. Heterotrophic NaCl: Lactic acid bacteria, soil and 0.2-6.5% Wide range organic sediments, pH: compounds beach sand, 4.4-9.6 decomposition and aquatic and synthesis terrestrial vegetation, and ambient waters Gemmatimonadetes Gemm-3 Uncultured Heterotrophic Neutral more likely to be Compost, bacteria Adapt to low pH decomposing organic Neutral soil moisture, matter than fresh Aerobic biomass, polyphosphate accumulation Proteobacteria Caulobacteraceae Brevundimonas sp. Heterotrophic, NaCl: Denitrification Soil (alpha) Motile, 0-3% Oxidase and catalase Sea sediment, Aerobic pH: 6-10 positive sludge, sand and fresh water Caulobacter sp. Mesophilic and NaCl: Cellulose Aquatic cellulolytic, 0-2% decomposition habitats, both Adapt to redox- Optimal fresh water and fluctuating pH: marine, environments 7.5-8.5 Nutrient poor, Soil Bradyrhizobiaceae Balneimonas sp. Heterotrophic, NaCl: Hydrolyse Soil, Non-motile, 0-2% hypoxanthine, Roots, Aerobic pH: Cellulose-producing Hot spring 5.0-9.0 Hyphomicrobiaceae Devosia sp. Heterotrophic, NaCl: hydrolysis of cellulose Soil Motile, 0.5-2% and urea Aerobic pH: 6.5-7.5 Rhizobiaceae Agrobacterium sp. Heterotrophic, NaCl: horizontal gene Plant roots, Motile, 0-5% transfer to cause plant Soil Aerobic pH: tumors 6.0-10.0 hydrolysis of urea and starch catalase and oxidase activity Rhodobacteraceae Albirhodobacter Heterotrophic NaCl: oxidase and catalase Marine habitats sp. Non-motile, 1-9% activities Facultative anaerobic pH: 16.0-0 Phyllobacterium Mesorhizobium sp. Heterotrophic, NaCl: Form roots nodule Soil, Adapt to both acidic 0-2% P dissolution, Sandstone, and alkaline habitat pH: L-tryptophan Limestone 3.0-10.0 metabolism Acetobacteraceae Acetobacter Heterotrophic, NaCl: Acetic acid producing sugary, acidic Aerobic 0-1.5% Sugar fermentation and alcoholic pH: habitats 3.0-8.0 Sphingomonadaceae Kaistobacter sp. Heterotrophic na Organic matter Plant roots, decomposition, Soil, Methane enrichment Deep seawater Sphingomonas sp. Chemoheterotrophic, NaCl: metabolize a wide Soil, Aerobic 0-1% variety of carbon Water, pH: sources (including Plant roots, 4-12 pollutants) Nutrients poor Proteobacteria Alcaligenaceae Alcaligenes sp. Heterotrophic NaCl: Hydrolyse Saline soil (beta) Motile, 0-10%, carbohydrate catalse, Saline water Aerobic pH: nitrate reduction and 6-11 oxidase positive. Produce hydrogen sulfide Oxalobacteraceae Pseudoduganella Heterotrophic, NaCl: catalase and oxidase Lagoon sp. Motile, 0-3%, positive, sediment Aerobic pH: chitin degrader Soil 5-9 rhizosphere Proteobacteria Alteromonadacea Cellvibrio sp. Heterotrophic, NaCl: cellulose, xylan, Soil, (gamma) Aerobic 0-2.5%, starch, and chitin Fresh water pH: degraders, 6-10 Nitrate reduction Moraxellaceae Acinetobacter sp. Heterotrophic, NaCl: Aromatic compounds Soil, Non-motile 2-5%, decomposer, Water Aerobic pH: Catalase positive 4.5-9.5 Enterobacteriaceae Enterobacter sp. Heterotrophic, NaCl: Synthesize an enzyme Saline soil, Mobile, up to 7% known as ornithine Seawater, Facultatively pH: 5-9 decarboxylase, Halophytes anaerobic Some strains rhizosphere, symbiotic nitrogen Waste water fixation Klebsiella sp. Heterotrophic, NaCl: Carbonhydrate Soil, With polysaccharide up to 7.5% metabolisms, rhizosphere based capsule, pH: 4-10 Dissolve phosphate, Facultatively synthesized anaerobic sideropheres. Some strains symbiotic nitrogen fixation Citrobacteria sp. NaCl: Utilization of citrate, Soil, 0.1-4% Lactose fermentation Water, pH: 3-11 Accumulation Wastewater uranium Halomonadaceae Halomonas sp. Heterotrophic, NaCl: Nitrate reduction, Estuaries, Mobile, 15-25% Carbohydrate Oceans Facultatively aerobic pH: 3-11 fermentation Soda lakes Catalase positive Psedomonadaceae Pseudomonas sp. Heterotrophic, NaCl: Oxidase and catalase Soil, Mobile, up to 25% positive, Water, Aerobic pH: Decompose diverse Plant 4.5-9.5 organics, including aromatic carbon Xanthomonadaceae Aquimonas sp. Mesophilic, NaCl: Oxidase and catalase Warm spring Heterotrophic, up to 2% positive, water Mobile, pH: 6-11 Acid production from Aerobic cellulose