THE PROBLEM: Sludge formation, silting, blue algae growth — Located in Bavaria, the Quellitzsee is a natural body of water measuring 6 hectares (14.82 acres), and a popular destination for swimmers and anglers. In the past, these leisure activities were occasionally hampered by strong blue algae blooms and in 2013, the authorities of the city of Döhlau discovered another problem: So much sludge had formed in the lake that immediate action was needed. SchlixX Plus was chosen as the appropriate treatment and it resulted in 75 percent of organic materials broken down, allowing for their Regatta to take place.

Project Overview:

Treatment and Solutions:
Located southeast of Hof in the Tauperlitz region of Bavaria, Germany, the Quellitzsee is a natural body of water measuring 6 hectares (14.82 acres) and a popular destination for swimmers and anglers. In the past, these leisure activities were occasionally hampered by strong blue algae blooms and in 2013, the authorities of the city of Döhlau discovered another problem: So much sludge had formed in the lake that immediate action was needed.

Plan A: An island made of sludge
The conventional approach – dredging the lake – and especially the subsequent disposal of the organic sludge, turned out to be too expensive. Instead, a different plan was decided on: The lake would be drained, the sludge would be dried out and then heaped to create an island in the lake. However, this approach had two major drawbacks: Firstly, the organic material would have remained in the water and continued to have a damaging effect in the future. Secondly, this would have meant cancelling a sporting event that is incredibly important to the region: the annual Hof Regatta, a prestigious highlight of the international canoeing season in which over 1000 people participate.

Plan B: The “mayoral” solution
The mayor of the city of Döhlau wanted to find a way around this. When looking for alternatives, he came across OASE’s procedure. After just one meeting, during which our experts explained the environmentally friendly way in which the SchlixX Plus microorganisms work, he was convinced that this was the solution that would save the lake and the regatta for the city and its residents. He brought together all the relevant decision-makers and together with councilors, officials and OASE experts, it was decided that an initial test run would take place during the quiet winter season, when there would be no fish or bathing: The lake would be drained of half its water, then SchlixX Plus would be applied to part of the lake.

By April 2014 everything was ready: The authorities had carried out preliminary tests to determine the sludge height and the special OASE boat set off to spread the necessary 1.5 tonnes (1.65 US tons) of SchlixX Plus over half of the Quellitzsee. Everything went perfectly – except the weather conditions. When checks were carried out, it was discovered that, due to the low temperatures, the sludge had formed a solid, impermeable surface. As a result, the applied material was not able to penetrate the sludge to take effect. However, the OASE specialists also found a solution to this challenge: They developed an injection procedure that enabled SchlixX Plus to penetrate even the lower layers of sludge.

The Successes:
To record the effects of applying SchlixX Plus, the authorities arranged for the sludge height to be regularly measured by divers – in secret locations to rule out any tampering. The results brought to light by the divers could not have been clearer: By June, the sludge height had already decreased by 10 to 15 cm (3.94 to 5.9 in). And by July 2014, an incredible sludge reduction of 50–75% of the original amount was announced.

The water authority, the health authority, OASE itself and the members of the fishing association drew a clear conclusion from their tests: Applying the product did not affect the quality of the water – but it did break down considerable amounts of sludge. There were other positive effects as well: The reduction in organic material removed a food source for the algae, making it more difficult for them to propagate. And all this cost significantly less than the conventional dredging procedure.

At the end of the treatment period, the original enormous sludge height in the lake had decreased to a layer of just 5 to 25 cm (1.97 to 9.84 in). This result pleased nature lovers, bathing visitors, anglers and of course the regatta participants and organizers alike.

THE PROBLEM: Odor pollution, sludge formation, oxygen depletion, threat of fish kills — Home to many waterfowl, ponds can be particularly susceptible to algae growth, sludge formation, oxygen depletion and fish kills. The reason? Feeding the birds, while well-intentioned, causes a greatly increased intake of phosphate and, in addition to waste, leaves and plant residue, leads to more and more organic matter being deposited on the bottom of the pond. Nearby residents, not to mention the local press, are very sensitive to such issues affecting their ponds, meaning that municipal administrators and their policies quickly come under fire. This was the case as a foul odor and the beginnings of a fish kill were noticed in the Schwanenweiher pond in Ostpark, a small park east of the town center of Landau.

Project Overview:

Background:
The total depth of the pond was only one meter (39.37 in), yet the sludge in the pond had already reached an average depth of 55 cm (21.65 in). This meant that more than half of the precious water volume was no longer available. The evaporation losses from the approximately one-hectare (2.47 acre) pond are offset by a freshwater inlet, which renews the total amount of water once over the course of a year. However, this inlet is very rich in phosphates, which further reduced the water quality. The increasingly poor water quality could be clearly seen and smelled. The local press started to take notice when dead fish were occasionally seen floating on the surface. Action had to be taken quickly – there was no alternative. Ralf Bohde from the town’s environment office described the goal succinctly: “Remove the sludge and improve the quality of the water.”

Treatment:
The first priority was to remove the sludge. Dredging the pond seemed unavoidable, but the costs would have gone into six figures, in addition to further six-figure costs for the disposal of organic material. But then the responsible parties came across an innovative and quick alternative, which also happened to be 80- to 90-percent cheaper: OASE water therapy with SchlixX Plus. The mineral-rich powder with an oxygen source and highly active microorganisms binds phosphate from the sediment, thus preventing the formation of algae. The microorganisms also significantly reduce organic sludge. A tonne (1.1 US tons) of SchlixX Plus was added into the Schwanenweiher pond from a small rowing boat.

The active ingredient release of SchlixX Plus is usually scheduled to take place over eight to twelve weeks – however, this was not the case with the Schwanenweiher pond, as it was on the brink of becoming a dead zone. The eutrophication process was already too advanced: A few days after use, the weather became cooler and darker after a heat wave. While sunlight penetrates the pond, its algae perform photosynthesis and supply oxygen. However, a lack of light stops this process, leading plants to use up the remaining oxygen. Consequently, the onset of darkness and the associated increase in oxygen consumption by algae had an unfortunate impact on the Schwanenweiher pond: Several hundred fish perished overnight due to lack of oxygen. OASE PeriDox was immediately used as an acute measure, to great success: The oxygen content in the water quickly increased, successfully preventing the water from becoming a dead zone.

Results:
Of an estimated 150,000 to 250,000 fish in the Schwanenweiher pond, the application of PeriDox kept the deaths down to just a few hundred. The follow-up measures a few months later resulted in a 55-percent reduction in sludge. The remaining sludge is no longer black and foul-smelling, but has a healthier, brighter colour and an earthy smell.

The critical state of Landau’s Schwanenweiher pond and the beginning of fish kill had attracted a lot of attention in the local press and in municipal politics. OASE’s innovative water technology solutions enabled the town’s council and environment office to counter the alarming state of the Schwanenweiher pond quickly and cost-effectively, ensuring that the pond can continue to serve as a place of recreation for residents for years to come. Its fish stocks and water values remain stable to this day.

THE PROBLEM: Sludge formation, silting — The Kleiner Russweiher, located Upper Franconia in Bavaria, Germany is a lake of considerable size, measuring 27 hectares (66.69 acres) in total. Part of a beautiful landscape, it forms the end of a chain of ponds and invites you to wander along its natural banks, swim, fish or even go boating. As well as appealing to the local population as a relaxing spot to visit, the lake also attracts large numbers of tourists every year, who are served by three camp sites and two hotels right on the lake shore. The absolute highlight of the Kleiner Russweiher is located on the southern bank. Here, visitors can enjoy the natural outdoor swimming pool, which is the largest lake-front mud bath spa in Bavaria.

Project Overview:

Background:
Over the years, the perfect idyll of the Kleiner Russweiher had lost its shine. Visitors to the pool had to wade further and further through foul-smelling sludge before they could swim. The increase in silt was also making fishing difficult. And a swimmer who crossed the lake every day reported shallow spots where he was even able to sit down.

It became clear to the authorities of the city of Eschenbach, who are responsible for the lake, that a noticeable amount of sludge was forming in the Kleiner Russweiher – and something needed to be done. However, after initial research, it quickly became apparent that the conventional solution for this problem was simply too expensive: Dredging and disposing of around 100,000 m³ (130,795 yd³) of organic sludge would have cost more than the city treasury could afford. And where could so much sludge have been stored before disposal?

The Solution and Treatment:
Thanks to numerous press reports on the conditions at the Kleiner Russweiher, the wider public were now aware of the problem – fortunately. When an Eschenbach resident happened to see a TV report by the Bavarian broadcasting service about how SchlixX Plus had been used to successfully treat the Quellitzsee, he immediately contacted the local authorities:

Wouldn’t this solution also be ideal for the local lake? The Eschenbach authorities acted quickly and invited OASE to a meeting with the people who run the lake-front spa, tenants and city representatives, who were then informed about the procedure. Some attendees were initially skeptical about whether “some kind of powder” could solve the problem, so it was decided that a test run would be carried out after the bathing season ended in September 2016. A prerequisite for the approval of the responsible authorities was neutral monitoring of the test so that results and developments could be understood later.

It was a difficult start. A boat designed especially for this large area and equipped with GPS equipment spread exactly 8 t (8.8 US tons) of SchlixX Plus over a specified area. However, at the time, none of the parties involved knew that exactly one week later, the Grosser Russweiher, a lake to the north, was to be drained into the Kleiner Russweiher. The effect was substantial: The flushed water swirled up the SchlixX Plus that had been applied – and also transported even more organic sediment into the lake in large quantities. As a result, the first treatment and also the data collected as part of the monitoring process came to nothing.

Successes and Results:
In April 2019, test no. 2 was given the go ahead. This time everything went smoothly, with very good results: After six months, the sludge layer had reduced by an average of 22 cm (8.66 in) over an area of 16.9 hectares (41.74 acres). This meant that over this period, 7.5 t (8.27 US tons) of SchlixX Plus had degraded a staggering 28,000 m³ (36,623 yd³) of organic material. And, when analyzed, the water showed the same excellent values as before in all parameters.

In 2020, the city of Eschenbach commissioned Oase to continue their treatment of the lake – this time also in the area of the lake-front spa, where around 9 t (9.9 US tons) of SchlixX Plus were applied over 18 ha (44.46 acres). The same method as before was used to check the effect: The distance from the surface of the water to the ground was measured and this was used to calculate the amount of sediment degraded. However, without checking the composition of the sediment. The result: At around 12,300 m³ (16,088 yd³) a considerable amount of organic material was degraded in the bathing area, but the clients had hoped for more based on the first treatment.

Nevertheless, SchlixX Plus had actually done an excellent job. This became apparent a short while later when the lake was drained: Sand banks emerged all along the shore area of the outdoor swimming pool, where sludge had been previously. And the sand had only a minimal organic content of less than 1%. This pleased visitors to the pool, but also the authorities. In the event of dredging, the disposal costs for inorganic sand are only a fraction of those for organic sludge.

On the one hand, sand is more pleasant for bathers to walk on than silt. However, there are other advantages, especially for water maintenance: Unlike organic sludge, it is not mandatory to dispose of sand at a landfill site, so it can easily be removed. And this has a massive impact on disposal costs: Compared to disposing of organic material, which costs about €100/t ($99/US t), the disposal costs for 1 m³ (35.3 ft³) of sand are roughly €3.50 to €4 ($3.82 to $4.36). (To compare the units of measurement: The mass of 1 m³ (35.3 ft³) of water is just under 1 t or 1.1 US t). So if you want to create more volume in a body of water by dredging the sediment, the resulting costs for disposing of sand are considerably lower.

Most importantly, however, the people of the region and the numerous visitors are once again able to enjoy a beautiful piece of nature: Fishing enthusiasts are pleased with the number, size and taste of the fish. And in 2020, the lake was also certified for excellent bathing water quality according to strict EU criteria.

THE PROBLEM: Sludge formation, algae blooms, foul gases, increased nutrient input — The Yanshan Garden public park in the Chinese city of Taicang invites residents and tourists alike to stroll through an area filled with views that present a harmonious composition of nature and architecture. The jewel in the park’s crown would ordinarily be the centrally located lake – that is, if the water wasn’t incredibly cloudy. Over the course of ten years, leaching, an excessive population of fish and algae growth have all led to a deterioration in water quality and a considerable development of sludge. Operators sought a cost-effective solution for treating the water that, insofar as possible, could be applied without closing the park. During their research, the operators came across Oase Professional and were able to receive the proper help from the Oase Water Technology experts.

Project Overview:

Background:
The park operators did not want to merely offer those seeking somewhere to rest and relax a place to explore nature undisturbed and free from cloudy water and foul smells. They also needed to meet the strict state requirements for surface water in China – specifically, quality level V. One of the restrictions imposed by this quality level is a maximum quantity of substances such as ammonia, phosphate and nitrogen. Quality level V water must also feature a visibility depth of at least 80 cm (31.50 in), in its original condition. The 2.5 hectare (6.18 acre) lake was a long way from this.

The Solution and Treatment:
Fast treatment against foul smell was a must and water analysis pointed towards treatment using SchlixX. The product binds phosphates into an insoluble and environmentally neutral mineral called apatite, thereby reducing the supply of nutrients. It also releases oxygen, which stimulates the microorganisms in the water to break down organic materials.

To provide targeted treatment for individual areas, the lake was divided into five sections from A to E. The first attempted treatment began in March 2021, but had to be interrupted due to simultaneous restoration work on the bank of the lake. This restoration work caused a considerable amount of additional nutrient input, which temporarily worsened the water quality even further and led to an algae bloom in February 2022. However, this unfortunate course of events did not prevent the Oase Professional experts from continuing to treat the water, this time, in a more appropriate setting: Only area E of the lake would now be treated to combat algae growth by phosphate binding and to remove the sludge using SchlixX, since this segment is only connected to the rest of the lake by a five meter (5.47 yard) wide channel and therefore offers a stable working environment.

Successes and Results:
Following the initial setback, significant improvement could be seen just one month after treating the lake in May 2022: The water in segment E was so clear that fish and even stones were visible at the bottom of the lake – a major success for the entire team and a visual delight for park visitors. Obviously SchlixX had done a lot of work.

The contrast with the other, as yet untreated areas of the lake was obvious. These areas had developed a thicker layer of sludge, were plagued by algae growth and had become even cloudier than before. The result in the treated area was so convincing that the operators made a plan to similarly initiate treatment of the remaining four areas once the renovation of the bank is complete.

THE PROBLEM: Siltation, sludge accumulation, oxygen depletion, fish kills — An Idyll at risk of disappearing, the lake Mühlenteich at Kloster Oesede in the town of Georgsmarienhütte is located in the middle of a European nature reserve. It is surrounded by wetlands and the diversity of its animal and plant species makes it subject to the Habitats Directive (it is what’s known as a Special Area of Conservation, or SAC for short). Increasing periods of drought and the growth of sediment were causing the water level to sink steadily, which eventually led to entire areas silting up. For several years in a row, fish were regularly dying due to the smaller water volume and the consequent lack of oxygen in the water. To preserve the lake as a nature reserve in accordance with the Habitats Directive and also preserve its value as a recreational area, this process needed to be stopped with minimal impact and lasting effect.

Project Overview:

Background:
After careful examination, the first idea of dredging the lake was rejected because the use of heavy machinery would have damaged the land too much. It was feared that nature and its biodiversity would no longer be able to self-regenerate. The aim was therefore to find an effective but low-impact solution that would preserve the entire biotope of the Mühlenteich – that’s where Oase came in.

Treatment and Solutions:
The solution was obvious to the Oase team: Lake therapy using SchlixX Plus, which ensures natural degradation of the biomass that would otherwise continue growing indefinitely. After an intensive environmental impact assessment, SchlixX Plus was first applied to selected places in September 2012, initially in order to observe changes in the properties of the sediment and any possible effects on the overall biotope. Further applications followed in 2013, 2014, 2018, 2019 and 2020 with the aim of further reducing the sludge layer and compensating for new siltation that naturally occurs outside the times when SchlixX Plus is applied.

At the same time, an extensive monitoring system was set up to document the results in depth over the long term. Since 2013, samples have been taken continuously at ten separate measuring points in order to detect changes in the sludge thickness and examine whether the biocomponents (plankton, macrophytes and macrozoobenthos) have been affected in any way.

Results:
The successes after a decade are clear to see: After just the first application of SchlixX Plus, the measured water depth rose to above 1 m (39.37 in) again in several places. The monitoring measures in 2013 estimated the sludge layer to be 83 cm (32.67 in), but by 2020 it was only 53 cm (20.87 in). Despite new sediment formation of about 3 cm (1.18 in) each year – due in part to the decomposed plant material of the yellow water lilies covering the surface of the pond – the sediment has been reduced by a third overall with just five applications.

Having less sludge means that there is a greater volume of more valuable water available. The sustainable water therapy using SchlixX Plus has therefore not only successfully stopped the siltation process – the increasing depth of the water has also created a more oxygen-rich habitat for the fish. There have been no excess fish deaths since and the fish population has recovered very well thanks to the significantly improved conditions. Furthermore, studies have shown that there have been no negative effects on the biocomponents of plankton, macrophytes and macrozoobenthos. During their on-site visits, most recently in 2020, experts were able to observe a species-rich biotope with higher distribution of amphibians and dragonflies. No wonder SchlixX Plus has now won the German Award for Sustainability.

THE PROBLEM: Nutrient pollution, sludge accumulation — The lakes at Dobson Ranch are part of a man-made drainage control system, that winds through the master-planned layout. Over the years, high nutrient levels from the main inflow feed and run-off from cultivated lawns and golf course turf, resulting in increased maintenance issues and costs, as well as accumulating organic sediment concerns. This was especially the case in Lake #8, which ends in a spillway and acts as a dam, causing it to be prone to sediment accumulation. SchlixX Plus was chosen as the appropriate treatment and the results say it all!

Project Overview:

Background:
The lakes at Dobson Ranch, a community in Mesa, AZ, are part of a man-made drainage control system, that winds through the master-planned layout. Over the years, high nutrient levels – carried into the lakes from the main inflow feed and from run-off from cultivated lawns and golf course on the lakes’ shores – have resulted in increased maintenance issues and costs, along with concerns on how to properly address the accumulating sediment in the future. This was especially the case in Lake #8, which forms the terminus of the system and ends in a spillway which acts as a dam and is particularly prone to sediment accumulation.

Treatment:
Water and sludge samples were taken and analyzed 3 months before treatment.
SchlixX Plus was chosen as the appropriate treatment as it provides 3 key benefits:

1. increases dissolved oxygen (DO) levels over a period of months
2. reduces sludge accumulation through microbial digestion
3. prevents the re-release of biologically available phosphate from digested sediment

Treatment was executed on November 9, 2022 and the dosage applied was 1,654 lbs of SchlixX Plus. To reduce dusting and loss of product to wind, an apparatus was used which pre-mixes the SchlixX Plus powder with water drawn from the lake and ejects it via submersed nozzles into the wake of the boat. The process took 8 hours to cover the entire 2.5 acre surface area.

Results:
Measurements and samples were taken two times in the 6 months following the treatment. Analysis of both showed significant changes in both organic sediment and phosphate levels. The sludge layer had been reduced by an average of 6 inches, with a water volume increase of 1.25 acre-feet and a >30% phosphate reduction. No negative effects on other parameters that could influence the overall ecosystem, habitability or usability of the lake water could be observed.