This research initiative intends to promote biodiversity in quarry rehabilitation thereby introducing a Constructed Wetland (CW) system to treat onsite generated domestic wastewater and impounding rainwater while recovering treated water and nutrients for reuse in quarry restoration. CWs are ecologically based engineering facilities designed to employ wetland vegetation and microorganisms to treat wastewater thereby imitating the same processes taking place within the natural wetland systems. The research therefore, focuses on optimizing wastewater treatment processes to meet local and international discharge standards while reserving the nutrients necessary for vegetation growth in the quarry. This integration is necessary to supporting the physical, chemical and biological improvement of the quarry land with value-addition along nutrient cycling and materials chain. The project is implemented at the cement quarry based at Tanzania Portland Cement Company (TPCC), Wazo Hill, Dar Es Salaam, Tanzania. The project is implemented in three phases: (1) system design and establishment phase (2) system stabilization phase (3) performance monitoring and analysis phase
System design and establishment phase will commence by conducting a site reconnaissance to gather baseline data necessary for the design work. The phase will be accomplished by putting in the quarry a pilot scale experimental setup. A Horizontal Subsurface Flow type of CW will be designed and constructed to receive wastewater from the septic tank which receives raw sewage from the flushing toilets in the quarry. The CW unit will also be designed in such a manner to receive impounding rainwater free flowing in the quarry.
The system stabilization phase will meant to create desired wetland conditions for wastewater treatment in the CW unit. Specifically, the phase will enhance the generation, growth and stabilization of microorganisms and plant species necessary for pollution abatement from wastewater. The main operational activity in this phase will be the control of wastewater flow rate in the CW unit.
Performance monitoring and analysis phase will involve sampling of wastewater, onsite and laboratory analysis of wastewater samples, data analysis and discharge of treated water to the quarry vegetation for rehabilitation and restoration purposes. During data analysis, the performance of this integrated process will be evaluated based on reductions of pollutant parameters from treated water in the form of organic matter content (BOD/COD), suspended Solids (TSS) and Faecal Coliforms (FC) concentrations. The performance will also be evaluated based on recovery of Nitrogen and Phosphorus concentrations in treated water and their impacts to the increase of quantity and type of biological species of flora and fauna in the quarry.
Successful implementation of this research project is expected to enhance the diversity of flora and fauna species as well as creating their habitats. The project will also provide a platform for wider application CW technology for onsite wastewater treatment in quarries. This will not only cut off operational costs associated with waste management at present, but also create a positive linkage between waste management and quarry rehabilitation. The research will also add the recreational and educational values of the mining sites.