A sewer system is proposed to ensure that sewage is collected and treated to hinder the water to pollute either the groundwater or the sourrounding reef. The sewer system consists of a sewage network and a waste water treatment plant. Residues of the waste water treatment plant can be used in a biogas plant. The sewage network is based on pipes and tunnels that transport sewage water from the households and other catch basins to the waste water treatment plant. The waste water treatment plant separates different leachables from the water and the residues can be used for the biogas plant or other use. Waste water treatment plants have a relatively high energy demand, it reaches up to twenty per cent of the energy consumption of a community. [1] Waste water treatment plants usually have different treatment steps. They are usually devided into mechanical treatment, biological treatment and chemical treatment steps. Also more advanced steps are available but seldom in practice because they are very cost intensive. [2] Sewer systems can fail due to different scenarios. On the one hand the can fail by hydraulic failure. Hydraulic failure means, that groundwater is leaking into the sewer system, because of leakage through the joints. On the other hand failure of the sewer system is based on structural failures of the pipesystem. [4]
Biogas plants are proposed as a part of the sewer system to make use of the accumulation of residues and to generate extra energy from it.
Currently five pump stations form the backbone of the sewer system on Bonair. Bonair plans to update the system with a 6th pump station soon. The waste water treatment plant on Bonair today treats around 4000 cubic meter a day. [3]
Interrelations between the sewer system and the other proposed systems exist in that sense, that the sewer system delivers a substantial progress in the prevention of environmental pollution, at the same time it consumes a reasonable amout of energy. By using the residues of the waste water treatment plant, which can be used in the biogas plant, a percentage of energy of the consumption can be compensated.
The other proposed engineering systems for the integrated energy system for Bonaire are solar rooftops and wind turbines. All of these products are incorporated in overall maintenance strategies and are beeing assessed by a mulit- objective optimization.
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[1] https://de.wikipedia.org/wiki/Kl%C3%A4ranlage#Biologische_Stufe
[2] https://en.wikipedia.org/wiki/Sewage_treatment
[3] https://www.webbonaire.com/en/wastewater/investing-in-sustainability/
[4] Abraham, D. M. et al. (1999): Development of prediction models for sewer deterioration, in: Durability of Building Materials and Components 8, S. 1257 – 126
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All sources last viewed 2018-02-12.