installation and maintenance

utilisation of sewage treatment plants

Sewage treatment plants are used as the second step of cleaning placed beyond the adjusted cesspool or a septic tank. There it is possible to clean only wastewater and water of similar kinds. The plants may not be used to clean industrial water, water from healthcare facilities, and water containing oil products. No wastewater containing any harmful substances may enter the plants (larger amounts of disinfection agents, acid or alkaline substances) of any concentration. Water from restaurants, guesthouses, etc. must be rid of fat and grease in the efficient grease catcher prior to entering a septic tank.

installation

The STP must be placed on a horizontal platform (optimally made of concrete) provided with a hole measuring of 500 x 500 mm, for the STP’s scooping mechanism, a feed cable and a passage for the hose (e.g. a heavy duty plastic pipe set into cement) for summer operation, if applicable. After the installation of the STP, part of the opening will be covered with a tin sheet. There is not limit on the width or the height of the platform. Generally it is about 10 cm high, made of gravel sand cement or crude brick work.

installation over a septic tank

The STP is to be installed over biozone 2 ("the last compartment") of the septic tank.

installation over a wastewater sump (cesspool)

In order to meet the condition stating that a STP should be used only as a second-step purification method, i.e. after a mechanical pre-purification process, we recommend to put a partition in the wastewater sump as to a separator, trap, allow to putrefy, and thereby sanitate insolvable particles in wastewater. Optimally, the partition should divide the sump at a ratio of 2:1, but no less than 1:1. The partition must be at least 1,300 cm high; ideally, it should reach the upper edge of the feeding drain and feature 3 elbows of at least 150 mm in diameter, where their lower edge should be about halfway between the bottom of the tank and the feeding drain, but no less than 600 mm high. This triple-elbow

device in the wastewater sump prevents the sludge from overflowing from the first part of the tank to the other. Between the upper edge of the partition and the top of the sump, there must be a space of at least 300 mm.
In case the STP has to be installed over a sump where the placement of a partition would be extremely difficult of impossible, the STP must be emptied and cleaned more frequently.
In such a case, we recommend to place the scooping mechanism opposite the feeding drain or to install a filter basket (not included in the price).

Minimum sump lid load (cesspool, septic tank) where the sewage treatment plant is to be installed must be constructed in respect of the plant’s load in full operation (filled with water, service operations) of the total weight of the plant / lid load, i.e. UH-0,5 model 780 kg / from 8000 N, UH-1 model 880kg / from 9000 N, and the UH-1,5 model 990 kg / from 10000 N. This applies to shallow placing of the sump. In case of deep placing, it is necessary to consult this with the entity involved in the construction of the sump or its installation based on the total amount of filled soil.
Before the installation of the HERVA sewage treatment plant itself, it is always absolutely necessary to secure the discharge of the sump (cesspool, septic tank) up to approx. 1/3 of the total depth.

summer and winter operation

During the operation of the STP in summer, if the septic tank or the existing sump is shallow (i.e. with its upper edge almost on the same level as the ground), the existing drain should be provided by a hose into a concrete rim. With deep-set septic tanks/sumps, a brick wall has to be built around the well upward from the ceiling of the tank/sump in order to install the scooping mechanism (over biozone 2) and the sludge drain (under biozone 1).
The brick-walled well is then filled out with earth up to ground level. In this case, the draining of purified water can be effected through an underground frost-proof pipe, provided the above conditions are satisfied.
In existing septic tanks, the drainage uses the existing opening.

During the operation in winter, the width of the hose should range from 1" to 5/4". It should be attached to the drain situated underground in the frost-proof depth in the wall of the septic tank/sump. Suitable material for the drain is, for example, ceramic clay, cast iron or heavy-duty plastic. The inner diameter of the pipe should not be less than 100 mm: optimally 150 to 200 mm. Where the purified water is allowed to seep into the ground, the drain pipe must be long enough to ensure the necessary capacity required for winter operation. If the ground is clayey, the drain passage should be filled with gravel sand (and complemented with a soak-away) for greater capacity. This type of drainage or winter filtering requires adherence to the respective norms.
Hoses for summer and winter operation may be left in place, because if the summer hose happens to freeze up, the water is drained automatically through the winter hose/pipe - and vice versa.
It is recommended to attach one 1" extension to the 5/4" drain opening to enable the attachment of a hose.

electrical energy input

Power engine - Siemens electrical single-phase motor, type 1LF7060 - 120W (or equivalent) uses 230 V current. Motor and the heating elements have their own switch, encased in a waterproof box. STP’s are also equipped with a meter of “hours of operation” in order to check if the particular STP works continuously.
For standard models, a 3 x 1 mm2 to 3 x 1.5 mm2 CYKY conductor is used; automatic models require a 5 x 1 mm2 to 5 x 1.5 mm2 CYKY conductor. The circuit is secured by an independent circuit breaker.
It is recommended to provide the front-end protection using a circuit-breaker with a C2 earth-leakage circuit-breaker (with standard version), or B6 (with automatic de-slurring version) 230V, Iv 0.03 mA
Power supply for the sewage treatment plant is to be provided is accordance with a corresponding norm and it will be checked before putting into operation.

A custom-made version – a plant with a thermostat securing the automatic switch-on of the heating system when the temperature drops in winter to secure optimum function of cleaning

basic conditions for installation:

additional conditions

Maintenance of the STP consists mainly of frequent checking of the operation and regular draining of the sludge through the opening in the front wall of the tank. It is recommended to clean the entire unit at least once a year.
Detailed directions concerning the operation and maintenance of the STP are contained in the Operating Manual.
When stabilized, the sludge can be taken to compost or used for supplementary fertilization. In septic tank installations (if they are large enough), it is possible to reverse the operation by draining sludge back into biozone 1. If this is done, it becomes necessary to empty and clean biozone 1 regularly about once or twice a year. The purified water may be drained into a surface water stream or into the sewage system or it can be used for fertilization or garden watering.

When ordering or before installing the STP, we require the information on the depth of the hole intended for the STP.

Guaranty: 12 months from putting into operation; maximum 15 months from taking over the sewage treatment plant and putting it into operation.