TOPAS S treatment plants are manufactured for a variable inflow depth up to 1.2 m below ground. They are available in sizes 5 – 8 PE as circular tanks and for capacities of 10 – 400 PE as rectangular steel-plastic tanks.

The steel-plastic construction of larger treatment plant tanks is patented. The principle of the patent is that the structure’s stability is provided by profiled galvanized sheet metal. The plastic ensures the tank’s watertightness and protects the galvanized sheet metal from corrosion. The result is stability and rigidity of the structure, which cannot be created from plastic alone at an acceptable cost.

Both types have similar technology, but the TOPAS R-BASIC type does not include a control unit. The TOPAS R-BASIC technology includes an inflow tank, activation tank (bioreactor), and sludge tank, with the inflow tank connected at the bottom to the activation tank, forming a “connected vessels” system. In contrast, in the TOPAS S system, the inflow and activation tanks are watertight separated, and wastewater is pumped from the inflow tank to the activation tank. This makes the inflow tank also function as a pumping station and simultaneously serves to accumulate surge inflows.
Generally, TOPAS R-BASIC treatment plants are suitable for installations where the inflow sewage line is buried up to 0.7 m below the ground. TOPAS S are suitable for greater inflow depths, up to 1.2 m, where in other types of domestic WWTPs, it is necessary to precede with a pumping station or the treatment plant needs to be expensively concreted.
TOPAS R-BASIC treatment plants are designed only for permanently inhabited buildings, while TOPAS S treatment plants can be installed for both family homes and for cottages, i.e., recreational facilities with intermittent operation.


The TOPAS S WWTP is the first treatment plant with independent testing of functionality after 3 and 6 months without sewage inflow. The testing institute SZÚ in Brno conducted tests on 2 TOPAS S WWTPs with sewage inflow interruption for 3 months and 6 months. Upon resumption of inflow, both treatment plants achieved a 97% treating efficiency. Serially produced and certified TOPAS S WWTPs (CE product) were used for the testing.

Certification of testing TopolWater, s.r.o. received the GRAND Prix award for this product at the international fair For Arch 2018 in Prague.


A  Inflow Tank (Accumulation)
Activation Tank (Bioreactor)
Sludge Tank
Technology Box
E  Sand filter
F  Chemical Dosing

A  Inflow Tank – serves to capture and grind coarse impurities, to homogenize sewage, and for denitrification (removal of nitrates from wastewater).

B  Activation Tank (Bioreactor) – this is where the biological treatment of wastewater occurs by microorganisms contained in the “activated sludge”. Aeration provides the energy for this process. Further, it involves the oxidation of ammonia to nitrates and the separation of treated water from activated sludge.

C  Sludge Tank – used for storing excess sludge as a product of biological treatment. The principle is that the better the treatment plant works, the more excess sludge is generated for storage. If the treatment plant does not have a separate sludge tank and automatic desludging of the activation tank, sludge can leak into the clean water outflow even with minor maintenance neglect.

D Technology Box – the box is used to store the blower, control unit, electrovalves, and other electrical accessories.

Sand Filter – used for mechanical polishing of biologically treated wastewater. It is ideal for use with an automatic irrigation system.

F Chemical Dosing – a device for phosphorus removal or pH adjustment. It operates depending on the measured amount of wastewater and doses chemicals according to the set concentration of chemical per 1 m³ of treated water, preventing overdosing of the treatment plant with chemicals.


All types of TOPAS S treatment plants are fully self-supporting in their basic design and can be placed above or below the groundwater level. Treatment plants up to 8 PE can be installed on a sand base in stable substrates. Treatment plants over 8 PE require a concrete base. An inflow pipe is supplied with the treatment plant, which is installed during assembly according to the actual depth of the inflow sewage line. The inflow is led to the accumulation chamber of the treatment plant, which also functions as a pumping station. Therefore, the inflow can be installed at various depths below ground level as needed, ranging from 0.5 to 1.3 m below ground. If requested by the customer, the inflow can be made during the manufacturing of the WWTP. The outlet is always firmly built-in and is part of the product.


A Depth of inflow below ground level 0.5 – 1.2 m
B Total height 2.4 m
C Height of outlet above the bottom 1.4 m


After installation, the treatment plant is filled with water to a depth of about 1.0 m and then backfilled with sand or the original “reversed” soil, provided it does not contain stones (especially with sharp edges) larger than about 10 mm, which could damage the plastic shell of the tank. The shell of the treatment plant can also be protected from damage with dimpled membrane. The backfill under the connecting and outlet pipes must always be made with compacted gravel sand (preferably stabilized with cement) to prevent later settling of the backfill, which could damage the stability of the pipes.



The TOPAS S 5 treatment plant is equipped with a blower with a power input of 80 W and a voltage of 230V. The electrical installation of the treatment plant is complete, and it is not permissible to interfere with it under warranty. Each treatment plant is equipped with a 230V plug, connected to an acidur supply box. This plug is used for provisional connection and testing of the treatment plant with an extension cord. The connection from the property is made with a cable of at least CYKY 3J x 2.5 to the acidur electrical supply box – see wiring . If an electrician or installer with the appropriate professional qualification for the installation of electrical equipment is present during the installation, the supply cable will be connected directly to the treatment plant, and the provisional connection will be discontinued. The connection in the property and the electrical connection are carried out individually and are not part of the treatment plant delivery. It is essential that the power supply to the treatment plant is protected by a current circuit breaker.



The treatment plant can be manufactured in a single block with a tank for treated water (or possibly for storing excess sludge). The WWTP and the treated water tank with a volume of 2m³ are produced as one compact product. This achieves significant savings on transportation, earthworks, installation, assembly, and interconnection, which are completely eliminated compared to the installation of a separate WWTP and a separate tank for treated water. The treated water can be used as utility water or for garden irrigation.


Need advice on choosing a WWTP? Contact us, we will be happy to help you.