Sludge Removal ProjectHorlachgraben, Basins 1-3

The Horlachgraben is part of a former arm of the Main River and serves as a receiving watercourse for stormwater from the sewer system. This channel has no natural inflow and is divided into 13 basins. In 2024, only the first three basins were treated. Basin 1 is 1,013 meters long and 25 meters wide. Basin 2 is divided into two sections, each approximately 180 meters long; one is 19 meters wide, the other 7 meters wide. Basin 3 is 1,020 meters long and also 25 meters wide. The total water volume of the channel is approximately 120,000 m³.

THE PROCESS - CONTROLLING NATURAL PROCESSES

Specially conditioned bacteria and oxygen are used to treat the Horlachgraben. A patented process induces the bacteria to form exoenzymes. These enzymes are needed to break down complex compounds, such as those found in sludge, into simple compounds, since bacteria can only take up dissolved substances. This process is precisely controlled.

In addition to the bacteria, oxygen is introduced into the water in the form of dissolved oxygen and nanobubbles. Nanobubbles are bubbles smaller than 100 nm and have no buoyancy. They distribute themselves throughout the entire water column. This makes oxygen available exactly where it is needed most: at the bottom of the water body.

The project is scientifically supported by Hochschule RheinMain.

Mechanisms of Action at the Water Surface

• At the water surface, the bacteria efficiently take up nutrients, thereby restoring the natural balance. This limits algae proliferation.

• Nitrogen compounds are converted by the bacteria into atmospheric nitrogen through nitrification and denitrification, thereby removing them from the water.

• The bacteria are consumed by zooplankton. This returns, for example, the absorbed phosphate back into the lake's food chain.

• Through the additional nutrients entering the food chain, the animals living in the water body also benefit from the treatment of the Horlachgraben.

Mechanisms of Action at the Water Bottom

• With the help of oxygen, the bacteria, together with the exoenzymes, rapidly break down the organic sludge components into non-toxic substances.

• Nitrogen compounds are converted into atmospheric nitrogen through nitrification and denitrification.

• Carbon compounds are converted into CO₂.

• Phosphate is taken up by the bacteria, returning it to the water body's food chain.

• Nanobubbles cause a long-term increase in the redox potential at the lake bottom, leading to the fixation of phosphate through binding to iron or sediment particles.

• As organic material is removed, oxygen demand at the water bottom decreases, thereby reducing the potential for putrefactive gas formation.

The Treatment

The project began on April 26, 2024, with intensive sampling and sludge level measurement carried out by Hochschule RheinMain. On May 2, 2024, the first application of 6,000 liters of bacterial product took place - a product consisting of 98% water, bacteria, and enzymes. The bacteria were cultivated and conditioned for their use in special brewing stations. Depending on the specific task, this process takes 48 or 72 hours, or up to 9 days, under intensive oxygen supply and a constant temperature of 27 °C.

The project was supported and accompanied by:

• BluePlanet Germany GmbH

• City of Rüsselsheim am Main

• Hochschule RheinMain (scientific support and analysis)

• Lower Water Authority of Groß-Gerau District

• Engineering firm BGS Wasserwirtschaft GmbH, Darmstadt

• Water Protection Officer, City of Rüsselsheim am Main

Project Log

Through our project diary, you can learn more about the work and progress at the Horlachgraben.

DATE	ACTIVITY / RESULT
23–26 Apr 2024	1st intensive sampling and sludge level measurement was carried out by Hochschule RheinMain; samples were taken for water and sludge analysis; the basins were surveyed using sonar
28 Apr 2024	The 1st BPG solar nanobubbler was installed in Basin 3
02 May 2024	1st treatment with 6,000 liters of bacterial product for sludge reduction
08 May 2024	2nd treatment with 6,000 liters of bacterial product for sludge reduction
17 May 2024	4 BPG solar nanobubblers were installed in Basins 1 and 2
18 May 2024	1st treatment with 6,000 liters of bacterial product for the reduction of excess nutrients
22 May 2024	3rd treatment with 6,000 liters of bacterial product for sludge reduction
27–28 May 2024	2nd sampling and sludge level measurement was carried out by Hochschule RheinMain; samples were taken for water and sludge analysis; the basins were surveyed using sonar; the BPG solar nanobubblers were serviced
28 May 2024	The remaining 2 BPG solar nanobubblers were installed in Basin 3
29 May 2024	4th treatment with 6,000 liters of bacterial product for sludge reduction
05 Jun 2024	5th treatment with 6,000 liters of bacterial product for sludge reduction
12 Jun 2024	6th treatment with 6,000 liters of bacterial product for sludge reduction
22 Jun 2024	2nd treatment with 6,000 liters of bacterial product for the reduction of excess nutrients
24–25 Jun 2024	3rd sampling and sludge level measurement was carried out by Hochschule RheinMain; samples were taken for water and sludge analysis; the basins were surveyed using sonar; the BPG solar nanobubblers were serviced
26 Jun 2024	7th treatment with 6,000 liters of bacterial product for sludge reduction
03 Jul 2024	8th treatment with 6,000 liters of bacterial product for sludge reduction
13 Jul 2024	Treatment with BacBags was carried out→ BacBags are a biological solution for reducing sludge and organic deposits in water bodies. Enclosed in linen bags, the bacteria are released slowly over an extended period. The bacterial activity decomposes organic material and reduces COD and BOD levels (chemical and biochemical oxygen demand). The breakdown of organic substances reduces sludge and water turbidity.

News from the Horlachgraben in Rüsselsheim

Things happened at the Horlachgraben in Rüsselsheim: the changes were clearly visible in the sonar images. The water column - adjusted for water level fluctuations within a one-month period - had become noticeably larger.

This means that a significant amount of sediment at the bottom of the water body was broken down. At one point, it amounts to 62 cm. The sonar images also showed how the compacted sludge at the bottom of the water body was dissolving.

Innovation at the Horlachgraben: The First Solar Nanobubbler Platform

It marks a milestone in the application of environmentally friendly technologies: the first solar nanobubbler platform has been floating on the Horlachgraben in Rüsselsheim since April 28, 2024. Six more units followed by the end of May.

This innovative technology was developed by BluePlanet Germany GmbH in cooperation with Moleaer Inc., the global market leader in nanobubble technology. Additional partners in this project are Wakeunion and master electrician Norbert Fabian from Neukirch, whose expertise and dedication contributed to its success.

The highly efficient solar nanobubbler systems represent a genuine innovation: they generate atmospheric oxygen in water at an impressive transfer rate of up to 85%. The technology enables water bodies to be enriched with oxygen in a particularly efficient and environmentally friendly way. No electricity is required for this.

Thanks to modern remote monitoring technology, we always have a precise overview of the systems' function and performance. This guarantees constant control and the safety of the technology.