The second objective was to provide a basis for assessing potential improvements in the environmental performance of the system. The quantification of the environmental burdens for the provision of water and sanitation in the eThekwini Municipality first for the individual units and then for the system.
Abstraction and storage Appendix 2: Sludge disposal to sea
Inventory data
Emissions for the operating phase of the rest of the system are also shown. 3-19 Table 3 13: Mass inputs into the operating phase of the tertiary treatment plant per kiloliter of treated water 3-19.
Introduction
- Tools used
- Aims and objectives
- Thesis Structure
- References
The third, scenario analysis, looks at how changes to the system affect the environmental performance of the system. What are the environmental and social costs of providing extended water and sanitation services in the eThekwini Municipality.
System Boundaries and System Description
Inanda Dam
This design facilitates flocculation by accelerating the collision between flocs in the raw water and larger flocs that have already formed. Larger and heavier particles in the sludge settle to the bottom of the DAF unit.
Pumping and reticulation network
The sludge must be diluted to a solids concentration of 1% for disposal to the municipal sewer. The water recovered by centrifugation is pumped to the wash water recovery tanks and recycled.
Southern Wastewater Treatment Works
The efficiency of screw pumps increases from the minimum flow capacity to the rated capacity. Part of the sludge is recycled to the activated sludge unit and the balance is sent to a deep-sea outlet pipeline.
Durban Water Recycling Plant
Lime is dosed to the fast mixers at the inlet of the lamellar settlers to mainly precipitate phosphate as calcium phosphate and at the same time remove heavy metals. The lime is dosed to the water in the form of a slurry and prepared automatically.
Disposal to sea
Iron sulphate is used for phosphorus removal and can be dosed in the aeration tanks if necessary for decarbonisation in the slats. Oxygen is used for ozone production and can also be dosed to the aeration tanks and increase the aeration capacity of the secondary treatment plant.
Discussion
Life Cycle Assessment of Secondary Water Supplies, Report to the Water Research Commission, in press. Thompson P., (2000) Wiggins Waterworks Process Design Description, Umgeni water Internal report, Science Services Division, Umgeni Water, Pietermaritzburg, South Africa.
Environmental Life Cycle Assessment
Goal and scope
It was decided that the functional unit would be one kiloliter of the water produced from each subsystem at the set quality. It was decided that the functional unit would be one kiloliter of the water produced from each subsystem.
Life cycle inventory analysis
Again, the only input considered for the operation phase is the electrical energy associated with pumping. Thus, the inputs for construction of an activated sludge unit are shown in Table 3-10;.
Impact Assessment
This is due to the methane released from the decomposition of the log and pastures that have been submerged in the water. Production of concrete and transportation of materials used for concrete. As can be seen, most of the impacts are related to the production of steel used in construction.
Diesel, which is used to extract the raw materials used to make concrete, has a negligible contribution. The rest of the contributions come from the activated carbon filters (25%), the chlorinators (25%) and the chlorinators (9%). For the operating phase of the tertiary treatment plant, the impacts come from the chemical and electrical inputs to the processes.
The majority of the impacts are therefore due to the toxicity of the effluent from the pipeline during operation.
Interpretation
The top line of the graph shows the total operating load on the dam and the rest of the system. The impact of wastewater collection on the environment is solely the result of the energy used for pumping. As with the results of primary treatment, the performance level dominates the environmental profile of the secondary treatment plant, as can be seen in the table above.
This is because this unit is the tertiary facility's largest electricity consumer. It must be remembered that this is the ecotoxicity of the wastewater measured at the inlet to the outlet. From the graph it is clear that the environmental load of the system is largely due to the electrical input.
A second way to reduce the electrical load is to reduce the oxygen demand of the system.
COD IN COD OUT 1
This reduction in oxygen required for the process translates into major electrical savings through the aerators. It should be noted that these are preliminary results and will require further investigation to see if this change can be implemented at the plant. One of the factors to take into account is that the aerators have a dual function.
Therefore, it is necessary to investigate how reducing the air supply to the tanks will affect the mixing of the tanks.
10 20 Time [d]
Discussion
The detailed LCAs of the water supply, primary, secondary and tertiary systems clearly showed that the construction and decommissioning phase made a small contribution to the overall impact of each subsystem. In a study on the application of the LCA methodology to water management from the pumping station to the wastewater treatment plant, Rihon (2002) showed a similar finding in that the main effects in his study could be attributed to the secondary and sludge treatment phases of the system studied. Energy consumption in this phase (both direct and indirect) accounted for 67.5% of total energy consumption.
Hunt (1991) showed that the impact of secondary inputs was small (less than 5% of the overall impact) and. that including it did not greatly improve the results of the LCA. For the life-cycle inventories, any missing data were imputed using a worst-case scenario; This assumption was mainly applicable to the dam where very little monitoring of the emissions takes place. What this LCA does is to identify, quantify, interpret and evaluate the environmental impacts of the studied water system.
Rihon A.C., Lassaux S., Germain A., (2002), Application of the LCA method for water management from the pumping station to the wastewater treatment plant.
Social Impact Analysis
- Historical back ground
- Methodology
- Results
- Conclusions
- References
In the particular case of Inanda Dam, the major health impacts can be attributed to the relocation of the residents living in the dam's floodplain. The health impacts have been mitigated by the community's small size and the favorable environmental conditions in the surrounding areas. The construction of the pump and grid network has a high job creation score due to the labor-intensive nature of the project.
The health impacts stem from the nature of the work and the impact of the processes on the environment, which affects human health. The construction of the pump and grid network is awarded a high score due to the labor-intensive nature of the process. When quantified in relation to the functional unit, the job creation score for the construction and operation of the pump and mains network has the highest score.
For the impacts associated with the other development, most health impacts are associated with the use of electricity.
The Impact of Electricity Generation in South Africa
- Electricity production in South Africa
- Impact model used
- Environmental impacts of Electricity Production in South Africa
- Social impact of electricity production
- Alternative technology scenarios
- Discussion
- Conclusions
- References
South Africa is also the largest producer of electricity on the continent and a large proportion of emissions can be attributed to the power generation industry. Coal mining is a major cause of environmental degradation in South Africa (Van Horen, 1996), so the environmental impacts of mining contribute significantly to the overall burden of electricity generation. The following table shows a less detailed breakdown of the environmental consequences of consuming one kilowatt hour of electricity, as presented by Eskom.
It has been argued that health problems are related to the poor air quality in the region of the power stations. It is useful to consider how the environmental and social impact of the system would change if the generation mix in South Africa were different. The most controversial point in the nuclear energy debate is the handling of the spent nuclear fuel.
A study of the environmental impacts of electricity generation (Devezeaux, 2000) also highlighted some of the social impacts of electricity generation.
Use of LCA in planning water and sanitation infrastructure
- Introduction to scenario analysis
- Base case
- Option 1: Maximise the use of existing assets
- Option 2 - Recycle water
- Option 3: Construct new infrastructure
- Discussion
- Conclusions
- References
The base case is representative of the existing water and sanitation supply system in Durban. The sources of the impact of the base case have already been investigated in the interpretation and improvement analysis of Chapter 3. The total environmental impact of providing 200,000 thousand additional households with water and sanitation per day by maximizing the use of the existing assets is presented in Table 6-4.
New households still bear the burden of primary sanitation (those with water sewers). The results clearly show that the addition of the recycling plant reduced the environmental impact of water and sanitation provision. It is an innovative solution to the problem of urban waste and greatly reduces the environmental burden of the city.
As mentioned in the introduction, this is one of the main objectives of this thesis. In this study, the distribution of the filled bottles to consumers was included in the calculation of the impact. More than 75% of the impact of global warming can be attributed to the production and distribution of plastic bottles.
Conclusions and Recommendations
- Conclusions
- Key questions revisited
- Recommendations
One of the unexpected findings was the low environmental impact of the dam for the LCA categories. The social impact of the provision of water and sanitation was investigated to create a more complete picture. The results of the social impact analysis differed from the environmental analysis in that the impact of the construction phase was found to be significant.
The application of the LCA technique resulted in a quantification of the environmental impacts of the dam. One of the most important results of this thesis is the development of a framework for the sustainable expansion of a water and sanitation system. What are the environmental antisocial costs of water and sanitation service delivery in eThekwini Municipality.
The results prove that the addition of the recycling plant has reduced the environmental impact of water supply and sanitation in eThekwini Municipality.
