Volute dehydrátor

The Volute dehydrator is used for the thickening and subsequent dewatering of sludge. The equipment is small and lightweight and can work in automatic operation with minimal maintenance requirements. The device guarantees the thickening of activated sludge to at least 18% of dry matter, for sludge from municipal WWTPs.

The device is produced in several lines, and thanks to its low investment as well as operating costs, it is suitable mainly for industrial treatment plants and municipal treatment plants from 1,000 to 10,000 PE. Another great benefit of this device is the ability to thicken secondary sludge directly from the activation, which may eliminate the cost of the construction of storage tanks within the design of a new WWTP.

Advantages

1. Reduction of construction costs
The dehydrator contains a thickening zone that eliminates the need of thickening the sludge before its inflow into the device. The dehydration drum forms a compact structure together with supplementary devices that allows you to minimize spatial requirements.

2. Reduction of operation costs
The dehydrator is designed in such a way that it is protected from clogging. This minimizes the requirements for rinsing water and operation. The energy consumption of the dehydrator is very low (0.3 - 2.15 kW).

3. Efficient dewatering
The device dehydrates sludge with low dry matter concentration directly from the activation part and produces a sludge cake with the dry matter content of about 20 – 25%.

4. 24-hour automatic operation without attendance
The dehydrator is able to work in continuous automatic mode, incl. dosing of chemicals. The time requirements for its maintenance and operation are minimal (approx. 5 min/day).

Process description

The dehydration drum consists of a volute rotating at a constant speed under a layer of fixed and movable lamellas. The volute pushes the edges of the movable lamellas that continuously move in the gaps between the fixed lamellas during the rotation of the volute. In this way the space inside is cleaned, thus preventing clogging. Sludge water is then drained through the gaps between the lamellas. The gaps between the lamellas get gradually smaller towards the place where the sludge cake is removed. The gap between the lamellas is first 0.5 mm in the thickening zone, 0.3 mm in the dewatering zone, and at the end the gap is 0.15 mm. The end compression plate increases pressure onto the sludge cake to achieve more efficient sludge dewatering.

Basic layout and operation of the VOLUTE DEHYDRATOR

1. Sludge is pumped to the operation tank with a sludge pump. To ensure a constant supply quantity of sludge, the operation tank contains a manually adjustable overflow from which sludge is routed back to the storage tank of thickened sludge.
2. Flocculant is dosed into the flocculation part of the operation tank and flocculated sludge is drained to the spiral of the dehydration drum.
3. Sludge routed into the dehydration drum is concentrated by means of gravity in the concentration zone and further moved to the dewatering zone with the use of the volute.

* DS - Absolute dry matter of sludge

Aerobic Thermophilic Stabilization (ATS)

Sludge stabilization is a process in which organic substances are degraded. When the ATS technology is used, this reaction is carried out with the use of aerobic microorganisms. In this process, energy is released from sludge, causing heating up to more than 50° C. In this way such high speeds of degradation of organic substances are achieved that 7 - 9 days of storage suffice for the process. The metabolism of aerobic organisms leads to the inactivation of pathogenic bacteria and viruses, i.e., to hygienisation, and therefore a valuable fertilizer can be obtained.

This technology is mainly suitable for biological wastewater treatment plants from 5,000 to 50,000 PE, i.e., where building a gas management facility would not be economical.

An advantage of ATS as compared to AD is a considerable saving of investment costs, as the reactor is several times smaller. The technology also solves the issue of sludge hygienisation, and it can be suitably deployed in food-processing WWTPs or for intensification, where the existing equipment does not meet the capacity and there is no room for its extension.

Advantages

• Saving 2/3 of the volume of sludge management
• Low investment costs
• The result is a valuable type A fertilizer
• Tested technology (more than 25 years)
• Stabilization and hygienization carried out at the same time
• Short storage times
• Low spatial requirements
• High process stability
• Process flexibility
• Possibility of operation expansion
• Use in industry and in the municipal sphere
• The ATS technology meets the requirements of international regulations, e.g., US EPA 503

Description

Suitable for aerobic thermophilic processing are excess sludge and a mixture of primary and secondary sludge, and also, e.g., liquid manure. If hygienization is required besides stabilization, storage for at least 23 hours at a temperature greater than 50° C must be achieved. Two-stage equipment of the ATS type, with discontinuous operation, meets these demands. Once a day, stabilized and hygienized sludge is removed from reactor 2 and transported to the balancing tank. After the removal of stabilized sludge from reactor 2, this reactor is refilled with partly stabilized sludge from the pre-heating reactor 1. Reactor 1 is then filled with raw sludge. In larger systems, individual stages may consist of more tanks. In the first stage, temperatures between 35° C and 50° C are achieved, and in the second stage between 50° C and 60° C.