Summary
Contaminated water must be treated before it can be re-used as drinking or service water. This is also the case in remote complexes, e.g. holiday resorts or hotels, that are not connected to a central sewerage system. Apart from wastewater, large amounts of waste are also generated at these sites, which are very expensive to transport to central facilities. Since both waste streams comprise a large organic component, it is practical to treat them together. The objective of the project was therefore to develop an overall concept for the combined decentralized treatment of waste and wastewater. The treated material waste streams were to be recycled for further utilization and the concentrates subjected to microbial metabolism. The concept is based on anaerobic bioreactors that can treat biowastes along with the wastewater concentrate.
The process involves using membrane technology to treat the wastewater, followed by anaerobic digestion of the resulting concentrate together with biowastes. After completing bench scale tests, the process was implemented in a pilot plant.
Results:
- The highest rate of biogas production achieved by the mixture of biowastes and wastewater concentrate was 573 mL/h. This confirms the significant improvement in biogas production by anaerobic digestion, enhancing both process stability and gas yield.
- Without pH regulation the specific rate of methane formation is about 34% higher.
- The minimum requirements for BOD5 (≤ 40 mg/l) and COD (≤ 150 mg/l) can be maintained in a membrane tank, depending on the membrane and operating conditions.
- The membrane remained operational during the entire process and retained about 95% of contaminants in the wastewater concentrate.
- Irrigation with the permeate largely promotes plant growth and has no negative impacts. It thus presents a suitable avenue of re-use.
