Road dust mitigation using soya bean urease enzyme induced calcite precipitation technique

Abstract

Uganda as a developing country roads play a role of transporting cargo and passengers from one geographical region to another. However, only 18 % of the total network is paved and the remaining 82% is unpaved, dusty and impassable when wet. Mechanical and chemical methods have been employed to mitigate dust. Biotechnology technique for stabilisation of earth soils, however, provides a sustainable dust mitigation method. Enzyme induces calcite precipitate (EICP) and microbial induced calcite precipitate (MICP) techniques are the two most studied bio-technical processes. EICP is a bio-inspired process employing enzymes and MICP is a bio-mediated process involving use of micro-organisms which secrete enzymes to catalyze urea hydrolysis to ammonium ions and carbonate ions. Carbonate ions combine with soils combine with soluble calcium ions to form a precipitate which acts as a natural binder. The purpose of this report is to give an overview of the various activities conducted in the study of road dust mitigation using soya bean urease, urea and steel blast furnace sludge.120g of concentrated soya bean urease were extracted from crude extraction using 500g ammonium sulphate salting at 40% of the crude urease solution. 2M nitric acid leaching BSF activated soluble calcium ions using a ratio of 10ml: 1g 120 minutes. 2M urea solution was obtained by dissolving directly 120g into tap water. Minitab17 was employed in the design of experiment and optimisation process. UCS load and water absorption was the DEO response surfaces. Urease concentration molar concentrations of urea and soluble calcium were the input factors. FTIR qualitative analysis was identified functional groups present BFS, urease and soils us the KBr mid-range wavelength. Ph 0f 6.8 and a 7.17% value of dust were obtained from sieve and ph analysis of the soils. The maximum UCS load and minimum absorption values were 2376.6n from run 20 and 6.5% from run 18 respectively (table 10). ANOVA determined the significance of factors statistically. The model predicted optimal biocementing formulation responses were verified by applying the model; hence, the model was applicable. Comparative studies revealed EICP process using soya bean urease and activated BFS improved soil properties of road soils. Formation of calcite at the surfaces formed a coating which implied soil fines where binder together. Hence, dust mitigation. However, more research is needed to attain targets of less than 2% for water absorption, 4 MPa the unconfined compressive strength and sustainable sources with high enzymatic activity.