Onsite sewage facility | EPFL Graph Search

Onsite sewage facilities (OSSF), also called septic systems, are wastewater systems designed to treat and dispose of effluent on the same property that produces the wastewater, in areas not served by public sewage infrastructure. A septic tank and drainfield combination is a fairly common type of on-site sewage facility in the Western world. OSSFs account for approximately 25% of all domestic wastewater treatment in the US. Onsite sewage facilities may also be based on small-scale aerobic and biofilter units, membrane bioreactors or sequencing batch reactors. These can be thought of as scaled down versions of municipal sewage treatment plants, and are also known as "package plants." The primary mechanism of biological waste recycling in the natural environment is performed by other organisms such as animals, insects, soil microorganisms, plants, and fungi, which consume all available nutrients in the waste, leaving behind fully decomposed solids that become part of topsoil, and pure drinking water that has been stripped of everything that can possibly be consumed and utilized. This natural biological purification requires time and space to process wastes. In virtually all engineered onsite sewage facilities, recycling and decomposition by natural organisms is still the primary mechanism of sewage disposal. Giving the organisms the time they need to decompose wastes is accomplished by establishing minimum sewage retention and settling times, and minimum liquid flow distances between sewage disposal sites and surface water or water wells. It is normal for animals such as mice, rats, flies, and parasites to participate in the fully natural biological waste recycling process. Engineered facilities typically attempt to exclude them to prevent out of control population explosions and infestation, and prevent spread of vermin and disease.

Performance and User Acceptance of GDM Filters for HWTS in a Rural Community of the Occupied Palestinian Territories

Alexis Baron

As everybody knows, access to safe water is vital for human beings. It is also considered as a human right to have access to safe drinking water, free from pathogens that can cause illness and death. According to the World Health Organization (WHO), unsafe water is still a part of the daily life of millions of people on Earth. As it is not always possible to build centralized treatment facilities, household water treatment and safe storage (HWTS) is a promising alternative for many remote areas in developing countries. It is in this perspective that the Italian NGO named Cesvi targets unserved communities of South Hebron in Palestine. It has the goal to provide HWTS units to households. These HWTS units are composed of a gravity-driven membrane (GDM) filter. The water is pushed through the membranes by the pressure of the water column. It can allow high bacterial removal and requires no energy and low maintenance. That’s why it is a very interesting technology for household scale. An valuation of the technical performance and the user acceptance of 9 HWTS units set up in the community of Khirbet Ghuwein was the main focus of the present study. The results have shown that most of the filters have a log-removal value (LRV) equal to 2 or more, while LRVs of at least 4 are obtained in the laboratory. However, this corresponds to a comprehensive protection according to the WHO international scheme to evaluate household water treatment technologies. The calculated removal efficiency of the filter can be influenced by the concentration of bacteria in the raw water, how the system is operated and the quality of the internal connections of the system. Nevertheless, it allows to observe the removal of total coliforms but also of E. coli, even if the latter were not very present in water. In contrast, GDM filters allow a high removal of suspended particles. Finally, the data do not allow to judge the safety of the water produced, as the HWTS unit seems to be sensitive and favorable to recontamination and regrowth of coliforms. The HWTS units are globally used by the households even if their use tends to decrease over time. Most of the users seem satisfied even if they are bored by cleaning the HWTS unit and think that it takes too many operational efforts. In addition, most of them would not be willing to buy one if it was not provided by the NGO. It seems that they used the filters without realizing the real purpose of them. It is very important in this kind of projects to accompany the delivery of filters with a workshop explaining the interest of such HWTS units and the proper way to use and maintain them. Despite the results that are not as conclusive as expected, the application of GDM filters in easy-to-use HWTS units is very promising but it still needs studies, applications, and improvements to allow a significant impact on the field.

2019

Performance and User Acceptance of GDM Filters for HWTS in a Rural Community of the Occupied Palestinian Territories

Alexis Baron

2019