TechInfo: Sludge Treatment Options

The question on how the access sludge will be treated arises in every project. There are several methods for sludge treatment for which the basics have been stated in sludge treatment options in our Products & Services section. Here you find a more technical description of the individual options. If you would like even more details, please contact us .

Sludge drying beds

BIO-4 sludge drying beds normally consist of two separate tanks, which are located directly next to the BIOCOS® lines. The walls of these tanks are lined with draining plastic sheets, covered with fleece. Fleece is a synthetic material and works like a classical coffee filter. It holds back the excess sludge. The supernatant water (water between the bacteria flocks), however, drains through the filter and the draining plastic sheets back to the plant's pumping station and from there back into the BIOCOS® lines.

Some excess sludge is removed from the process and pumped into one of the drying beds after each BIOCOS® cycle. The storage capacity in one sludge drying bed is sufficient for the one to three months drying time. While one bed receives the wet excess sludge from the BIOCOS® lines, the other bed has enough time for drying.

The excess sludge drying beds are covered and constructed air and water proof. To speed up the sludge's natural drying process, the air blowers of the BIOCOS® lines will suck fresh air through the plant and ventilate the surface and the side areas of the drying excess sludge. The sludge starts first drying up its surface, which cracks open. This allows fresh air to get into deeper excess sludge drying zones. Because of that drying surplus sludge does not get anaerobic and almost does not smell. For a last hygienization, the dried excess sludge can be mixed with quick lime and bark mulch and be used as a carbon, nitrate and phosphorus enriched fertilizer.

Sludge thickening process

We offer BIO-4 sludge thickening as an alternative to BIO-4 sludge drying. BIO-4 sludge thickening is a simpler process with lower investment costs.

Some excess sludge is removed from the process and pumped into sludge thickening tanks after each BIOCOS® cycle. The wet excess sludge is accumulated inside the tanks, and supernatant water flows back via a scum board into one of the aeration tanks of the BIOCOS® lines.

Periodically, the accumulated wet excess sludge can be sucked out by a tank truck and can be brought to a larger municipal waste water treatment plant, which normally has some kind of sludge stabilization process. Alternatively, the accumulated sludge can be used as a carbon, nitrate, and phosphorus enriched fertilizer for reclamation areas.

Sludge dewatering units

First, analogue to BIO-4 sludge thickening, the aerobically stabilized excess sludge is thickened. Periodically, the thickened excess sludge from the bottom of the tanks is pumped into an electro mechanical excess sludge dewatering device to reduce the water content to a concentration of approximately 15-20% DR with the support of additional flocculent. The supernatant water of the dewatering process is pumped back into the BIOCOS® lines. The dewatered, “paste like” excess sludge is discharged into a storage container and can be used in four different ways:

•  The partly dewatered and stabilized excess sludge can be used as carbon, nitrate and phosphorus enriched fertilizer for reclamation areas.

•  For final hygienization, the partly dewatered excess sludge can be mixed with quick lime and bark mulch and then be stored at a covered (rain water proof) composting site. After a minimum of one month retention time, the sludge can be used as a carbon, nitrate, and phosphorus enriched fertilizer for reclamation areas.

•  For plants with at least 50.000 PE, the partly dewatered and stabilized excess sludge can be periodically fed into biogas digesters to produce biogas. Biogas can be used to produce electricity and heat. The retention time of the excess sludge inside the biogas digesters is approximately 20 days. For final hygienization, the fouled and dewatered excess sludge from the fermentation process can be mixed with quick lime and bark mulch and then be stored at a covered (rain water proof) composting site. After a minimum of one month retention time, the sludge can be used as a carbon, nitrate, and phosphorus enriched fertilizer for reclamation areas.

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learn more about what we can do for you, please get in contact with us and we will put you in touch with one of our experts.

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