For sewage water liquidation design comes-out of local conditions and of requests of investors and operators. The design of a suitable liquidation solution of sewage water due to the type of a development from the centralized system for de-sewerage of more objects or individually at each object. The variant of technoeconomic study processing according to the given locality, which considers and evaluates some variants with the recommendation of the best one.

The construction of a new refinery of sewage water or a reconstruction of a current refinery of sewage water must come up from the territorial configuration, development character, pollution character, possibility of draining the clear wastewater into the watercourse e.g. soakage object, demands for removal of sewage water, geological and hydro-geological conditions etc.

Domestic or small refinery of wastewater, at present exist a  line of industrially produced refineries of wastewater, which are produced by various producers in needed sizes  (from some EO to 500 EO) and designs (carbonaceous material removal by nitrification, denitrification or by supplemented micro-filtration). The choice of a concrete type depends on local conditions and demands of a quality of clear wastewater draining.

Septic tanks work as a sewage setting chamber, in addition the anaerobic removal of organic substance happens there and at the bottom comes to a gradual anaerobic stabilization of sediments. The most common septic tanks are with three or more chambers, divided by bars. Permeances and drains are protected by floating barrages. The optimal cleaning effects are at a hold-up period of 3 days and a specific effective range of a septic tank is for 1 connected inhabitant tentatively 0,6m3, but the total effective range cannot be less than 3m3. It is necessary to carry out the sediments from the septic tank at least once a year. In consideration of its cleaning effects the septic tank is acceptable only as a mechanic degree and then comes a biological cleaning, e.g. earth filter.

Earth filter is an equipment put in an isolated hole in which there is a filter cartridge laid next to an incoming and a colletive drainage system, where can exist purification organisms. The character of a cartridge designates the main processes, which participate on the purification  - the tank is used in a range from sand to gravel. To  1 inhabitant is a specific surface of an earth filter 0,75 to 1,0 m2. The earth filter with the connection of a septic tank presents a suitable purification of wastewater from isolated objects or their groups.

Root (vegetative) refinera of wastewater is in part a natural way of wastewater purification, based on a mechanical, physical-chemical and biological processes, ongoing in porous soil environment, in the water and by the help of wetland plants (reed). In our conditions it is recommended to count tentatively with an area needed for 1 inhabitant in the range from 7,1 to 9,6 m2.