1. Kasese Cobalt Company Limited (KCCL)
Kasese Cobalt Company Limited (KCCL) was looking for a process, which could treat its water effluent to standards required by the National Environmental Management Authority (NEMA).
KCCL’s parent company was informed by Environmental consultants of the World Bank/IFC of the possibility of cleaning mine waters with the use of biological treatment system i.e. Reed Bed Filter (RBF).
This way TransForm Aps (Denmark) got to know about the existence of the KCCL project through a World Bank publication. TransForm forwarded brochures to the World Bank, informing them about the existence of the rootzone technology suitable to treat mining effluent.
Then, discussions started between the two companies and a first visit was initiated in 1997. A feasibility study, investigating the technological aspects of the project, was later on carried out funded by the Danish Cooperation in Uganda. The conclusion of the study was that rootzone technology could be relevant for the treatment of the wastewater. Based on the study it was concluded that a pilot project should be initiated in order to clarify whether the technique in practice could be used for the treatment of wastewater from the KCCL Processing Plant.
Phase 1. Detailed Engineering and Construction. Preparation and adaptation of pilot project to local materials and products. Instruction concerning construction of pilot project including:
Phase 2. Instruction in construction of wetland and rootzone filter.
Phase 3. Training and instruction in operation and maintenance.
Phase 4. Evaluation and management training.
The result of know-how and technology transfer will enable KCCL to: Decide about full-scale project. Decide other treatment projects. Follow the standards of NEMA. Estimate final construction cost. Estimate operating cost. Secure environment protection.
Water purification by rootzone technology is well known, however conditions for the optimum purification require a combination of processes, methods and plant layout.
Water purification by natural methods activates the processes, which are particularly required. Conditions necessary for optimum purification processes require a combination of processes method and plant layout.
For polishing the effluent from the Kasese Cobalt Recovery Plant, a two step process flow ensures that the water goes through the required processes for optimum treatment. The first process is a wetland sedimentation plant with limestone and a second part containing a rootzone with active soil. An estimated precipitation of approx. 5.000 MT per annum should be included in the dimensioning.
Thereafter the treated effluent may be infiltrated, evaporated, led to a surface recipient or be utilised for irrigation of a timber production scheme, or other cultivation purpose. In connection with such schemes, environmental restoration of the areas below the KCCL lands should be carried out (on the border to and within the Queen Elisabeth Nat. Park Area). Wetland sedimentation with limestone.
Sedimentation wastewater, which has not completed flocculation, or which is still chemically reactive, will pass through a shallow planted wetland lagoon. The wastewater in this wetland sedimentation lagoon will be aerated via atmosphere oxygen.
Due to surface tension forces between the liquid and the plant stems, a more marked precipitation will occur in the proximity of the stems, thus, the surface tension forces of the plants, which will catalyse molecular formation and flocculation.Sulphate contaminate will react with organic compounds and precipitated as elemental and organic sulphur.
The retention time is determined on the basis of turnover rates. Current activities in the lagoons should be avoided as this may reduce the reactivity effect. The lagoon is constructed over a limestone filter, from where water is drained, thereby activating precipitation. This limestone layer will eventually clog, so requiring replacement of the limestone layer every second year.
The root zone/filter plant is a biological filter, where biological treatment of wastewater takes place in a soil volume, which is penetrated by the roots of Phragmites Australis. This root structure implies that the wastewater flows horizontally through the soil mass.
2. Lessor Ltd. – ecological office building
A better work environment and self-sufficiency in water, heating, wastewater treatment etc.
Newly planted rootzone filter plant for treating the waste water from the building. The water is recycled for landscape irrigation.
This construction was realized from an age old wish on behalf of the management to have a self contained building for the company. The company supplies salary administration systems for Danish business firms. The main idea has been to get a better working environment, independence from other tenants (reduced noise level), freedom in the indoor architectural arrangements, assurance of the capital of the company, improved expansion opportunities, more aesthetic qualities in the work environment. In the final project, a long line of indoor climate factors have been considered while a high degree of self sufficiency was obtained, especially in terms of water and heating.
Problems common to conventional office buildings such as radon radiation have been eliminated by using bricks rather than concrete, excessive heating avoided due to the geometry of the building, in particular the roof, static electricity was avoided by not using synthetic materials, especially carpets, high air humidity was obtained by establishing an irrigated lavacolumn in the nucleus of the building.
Rainwater is being collected from the roof and purified in the building’s own “water works”. while waste water is treated via septic tank in a rootzone filter and eventually utilized for landscape irrigation. Heating is done by the geothermal system, from where heat is distributed to floor heating system. Unsuitable materials have been avoided, whereby toxic gas emissions have been kept to a minimum.Significant electricity savings have been obtained through the ‘Intelligent House Control’ – system for all plugs, contacts, PTO’s for lighting, sensors , heat systems etc.
This building is also impressive by the fact that construction economy as well as o & m economy meets high standards and performs well in a life cycle analysis. During wastewater flow, water-contaminating compounds are bound to the soil colloids and other constituents of the rootzone are released to the atmosphere, through respiration, nitrification and denitrification and other processes. The turnover of organic substances occurs as a result of a diverse complex of aerobic and anaerobic microbial activity in the soil.
The aerobic activity is supplied with oxygen from the plant roots, as well as via the surface of the system. Thus aerobic activity is concentrated near the plant roots, and at same distance from the roots, anaerobic activity prevails. This mosaic of aerobic and anaerobic pockets provides optimum conditions for a wide range of active microbial organisms. Aerobic as well as anaerobic groups of organisms is necessary for a complete breakdown of the waste water constituents, and may be compared with the anaerobic and aerobic steps in a biological waste water treatment system.
3. Toarp ecological village.
Integrated rootzone-filter and sandfilter.
Through the development of this building project, it was sought to encourage a social and environmentally sound lifestyle. To design the buildings out from local cultural and local climate conditions, to select building materials from a environmentally and health considerate point of view, to use low technology for the establishment of a sound re-circulation system in the aspect of energy, resources and wastewater, to support a social atmosphere and activities by the construction of common houses and areas, and also an easy connection to official transport system. Wastewater treatment was designed for HSB Malmoe in 1992 and included rootzone / sandfilter treatment plant, aeration and water reservoir. The treated water, is re-used for irrigation of crops.
Toarp village consists of 37 family houses and common houses and areas for auto-sufficient ecological vegetables. There were, in 1995, 110 habitants.The following reductions has been achieved:
COD: 88% BOD7 > 97,6%
Total – N 91% Total – P 80%