Microbially induced carbonate precipitation (MICP) is a process that hydrolysis urea by microbial urease to fill the pore spaces of soil with induced calcium carbonate (CaCO3 ) precipitates, which eventually results in improved or solidified soil. This research explored the possibility of using dairy manure pellets (DMP) and palm oil mill effluent (POME) as alternative nutrient sources for Sporosarcina pasteurii cultivation and CaCO3 bioprecipitation. Different concentrations (20-80 g l-1 ) of DMP and POME were used to propagate the cells of S. pasteurii under laboratory conditions. The measured CaCO3 contents for MICP soil specimens that were treated with bacterial cultures grown in DMP medium (60%, w/v) was 15·30 ± 0·04 g ml-1 and POME medium (40%, v/v) was 15·49 ± 0·05 g ml-1 after 21 days curing. The scanning electron microscopy showed that soil treated with DMP had rhombohedral structure-like crystals with smooth surfaces, whilst that of POME entailed ring-like cubical formation with rough surfaces Electron dispersive X-ray analysis was able to identify a high mass percentage of chemical element compositions (Ca, C and O), whilst spectrum from Fourier-transform infrared spectroscopy confirmed the vibration peak intensities for CaCO3 . Atomic force microscopy further showed clear topographical differences on the crystal surface structures that were formed around the MICP treated soil samples. These nutrient sources (DMP and POME) showed encouraging potential cultivation mediums to address high costs related to bacterial cultivation and biocementation treatment.
Biocalcification through the use of ureolytic bacteria and biochemical activities has evolved in recent decades into a fervent resourceful effective technology suitable for soil stabilization, crack repair and bioremediation. Extensive studies have been carried out on numerous ureolytic bacterial species isolated from soils and sewage samples. However, very limited attention has been given to limestone caves with natural calcite formations as a possible source for isolation of ureolytic bacteria. In this study, bacterial isolates were recovered from limestone cave samples to determine their suitability for biocalcification. Twenty-seven morphologically distinct bacterial isolates were identified by partial 16S rRNA gene sequencing and their various genetic diversity was characterized according to their phylogenetic affiliations. Based on the molecular identification, Sporosarcina was the most abundant genus among all the ureolytic isolates, while the rest belonged to Pseudogracilibacillus and Bacillus genera. Analytical analysis on urease measurement showed that urease activities for the isolates ranged from 1·130 to 21·513 mol urea hydrolysed per minute, with isolate NB33 achieving the highest value and TSB4 achieving the lowest value. The estimated CaCO3 precipitates for the isolates ranged from 4·04 to 17·26 mg ml-1 , with isolate NB30 achieving the highest value and TSB20 achieving the lowest value. The findings in this study demonstrated that the ureolytic bacteria from limestone caves are promising bio-calcifying agents. SIGNIFICANCE AND IMPACT OF THE STUDY: Ureolytic bacteria continues to play an important role as microbial tools used in geotechnical engineering for soil biocalcification. Microbial strains with the ability to produce urease enzyme and induce calcium carbonate mineral are often isolated from soil, water and sludge samples. However, screening for these essential microbes from extreme regions such as caves are rarely investigated. In this study, native bacteria which were isolated from limestone cave samples are identified and characterized. The findings suggested that these ureolytic bacterial isolates have the potential to serve as suitable alternative microbial agents for soil strengthening and stabilization.
Biogranulation has emerged as a viable alternative biological wastewater treatment approach because of its strong biodegradability potential, toxicity tolerance, and biomass retention features. However, this process requires a long duration for biogranules formation to occur. In this study, magnetic powder activated carbon (MPAC) was used as support material in a sequencing batch reactor to enhance biogranules development for wastewater treatment. Two parallel SBRs (designated R1 and R2) were used, with R1 serving as a control without the presence of MPAC while R2 was operated with MPAC. The biodegradability capacity and biomass properties of MPAC biogranules were compared with a control system. The measured diameter of biogranules for R1 and R2 after 8 weeks of maturation were 2.2 mm and 3.4 mm, respectively. The integrity coefficient of the biogranules in R2 was higher (8.3%) than that of R1 (13.4%), indicating that the addition of MPAC improved the structure of the biogranules in R2. The components of extracellular polymeric substances were also higher in R2 than in R1. Scanning electronic microscopy was able to examine the morphological structures of the biogranules which showed there were irregular formations compacted together. However, there were more cavities situated in R1 biogranules (without MPAC) when compared to R2 biogranules (with MPAC). Dye removal reached 65% and 83% in R1 and R2 in the post-development stage. This study demonstrates that the addition of MPAC could shorten and improve biogranules formation. MPAC acted as the support media for microbial growth during the biogranulation developmental process.
Microbially induced carbonate precipitation (MICP) is a remarkable method that creates sustainable cementitious binding material for use in geotechnical/structural engineering and environmental engineering. This is due to the increasing demand for alternative environmentally friendly technologies and materials that result in minimal or zero carbon footprint. In contrast to the previously published literature, through bibliometric analysis, this review paper focuses on the current prospects and future research trends of MICP technology via the Scopus database and VOSviewer analysis. The objective of the study was to determine the annual publications and citations trend, most contributing countries, the leading journals, prolific authors, productive institutions, funding sponsors, trending author keywords, and research directions of MICP. There were a total of 1058 articles published from 2001 to 2021 on MICP. The result demonstrated that the volume of publications is increasing. China, Construction and Building Materials, Satoru Kawasaki, Nanyang Technological University, and the National Natural Science Foundation of China are the leading country, journal, author, institution, and funding sponsor in terms of total publications. Through the co-occurrence analysis of the author keywords, MICP was revealed to be the most frequently used author keyword with 121 occurrences, a total link strength of 213, and 152 links to other author keywords. Furthermore, co-occurrence analysis of text data revealed that researchers are concentrating on four important research areas: precipitation, MICP, compressive strength, and biomineralization. This review can provide information to researchers that can lead to novel ideas and research collaboration or engagement on MICP technology.
This paper presents an assessment of the start-up performance of aerobic granular sludge (AGS) for the treatment of low-strength (chemical oxygen demand, COD