Development of effective wastewater treatment has always been highly important in environmental protection. There are various ways of wastewater treating which are based on different criteria. Conventional wastewater treatment consists of preliminary, primary, secondary and tertiary treatments that are based on biological, physical and chemical processes. The most common biological process of wastewater treatment is a treatment with actived sludge. Bacteria, protozoa and microscopic metazoa use organic matter from wastewater as food and enhancement of biomass. Biological treatment offers high quality removal of suspended solids, BOD5 and nutrients and waste sludge can be used in composting. Conventional biological treatment is highly efficient, uses less space compared to non-conventional treatments and their functioning is not dependent on outdoor conditions. Some of the disadvantages of these treatments are the constant high electrical energy requirements and the design, supervision, maintenance, and the general cost of construction that would require highly skilled workers. There is also the issue of ecological disposal of the sludge waste. Prominent non-conventional wastewater treatments are ones with free surface and subsurface (horizontal and vertical) flow. Non-conventional treatments, compared to conventional treatments, are easier to use, cost less and are less complex in operation and design. Plants used in these treatments have higher efficiency of nutrient and heavy metal removal, raise biological diversity, don't distort the aesthetics of the landscape and can be used for composting. The disadvantage of that treatment is huge occupied area, sensitivity to nutrients increase, toxic and heavy metal levels and the requirements for constant water supply. Considering an increase of awareness in the use of energy resources, it is assumed that non-conventional wastewater treatment will be more applied in the future.