Treatment of engineering waste slurries by microbially induced struvite precipitation mechanisms

Abstract

With societal development, the growing scale of engineering construction, and the increase in environmental protection requirements, the necessity of engineering waste mud disposal is becoming increasingly prominent. In this study, microbially induced struvite precipitation (MISP) was introduced to treat engineering waste mud. The study mainly focused on: i) the optimal mineralization scheme for microbially induced struvite precipitation, ii) the feasibility of the process and the effect of reaction parameters on treating engineering waste mud with microbially induced struvite precipitation, and iii) the mechanism of microbially induced struvite precipitation in treating engineering waste mud. The results showed that the waste mud could be well treated with 8.36×106 cell⋅mL−1 bacteria, 10 mM urea, 20 mM phosphate buffer, and 25 mM MgCl2 at pH 7. The kaolin suspension could be effectively flocculated. The flocculation rate reached approximately 87.2% under the optimum mineralization conditions. The flocculation effect was mainly affected by the concentrations of reactants and heavy metals and the suspension pH. The X-ray diffraction (XRD) patterns showed a strong struvite (MAP) diffraction peak. Scanning electron microscopy (SEM) images indicated that under the optimal mineralization conditions, the crystals were large and showed prismatic shapes tilted at both ends with adhered kaolin particles. In summary, this manuscript provides an effective way to treat engineering waste mud, and the findings should have a positive effect on enhancing soil fertility and preventing secondary pollution.

Research on closed-loop utilization of engineering waste mud in engineering sites

“…The phenomenon of intensive abrasive wear is encountered in many branches of industry, most prominently the extractive, concrete, ceramic, and metallurgical industries [1,2]. Abrasion is also a very important consideration during the performance of machines and devices for earthworks, which applied in agriculture and construction [3,4]. Additionally, because of progress in the development of environmental protection, much research is conducted with the aim of prolonging the operation time of machines in direct contact with the materials used in waste recycling, e.g., metal shredder blades, transportation containers, and so forth.…”

“…According to statistics, the annual production of engineering waste mud in China is as high as 300 million cubic meters, accounting for over 60% of the nation's total construction waste [1,2]. This waste mud not only occupies land resources and pollutes the environment but can also easily lead to safety accidents due to the large volume of outward transportation and treatment [3,4]. Therefore, it is urgent to carry out the reduction and resource utilization treatment of engineering waste mud.…”