Improving small-scale wastewater treatment plant performance by using a filtering tertiary treatment unit

The demand for wastewater treatment plants purposed for a single household or groups of households continues to increase as the quality requirements for wastewater treatment become increasingly rigorous. Researchers are constantly searching for new methods to remove phosphorus compounds from wastewater that do not require the use of chemicals. This article describes a newly designed tertiary wastewater treatment unit that increases the effectiveness of the main small-scale (up to 1 m(3)/d) biological wastewater treatment unit. The tertiary treatment unit is filled with the sorbent material Filtralite P., after the main treatment wastewater flows through the filler without the use of electric power. A compact system consisting of a main (secondary) treatment unit and the newly designed tertiary wastewater treatment unit was tested in accordance with the harmonised European Standard EN 12566-3. During the testing period, no surplus sludge was discharged from the system, no reagents were dosed into it, the system only consumed 119 kW of electric power, and the treated wastewater contained < 1 mg/L of phosphorus. The total wastewater treatment efficiency can be explained as follows: COD - 95.2%, BOD5 - 99.2%, SS - 99.4%, NH4-N - 99.6%, N-t - 82.2%, and P-t - 91.8%. The system is efficient, the operational cost is relatively low, it does not use chemical reagents, and it is environment friendly.