Why sludge management is essential

Sludge management is one of the most challenging tasks of wastewater treatment plants. Sludge Finder 2 from Pulsar Measurement seeks to solve that problem.

Sludge management is one of the most challenging tasks of wastewater treatment plants. The Sludge Finder 2 from Pulsar Measurement seeks to solve that problem.

Sludge management and blanket control are crucial for any wastewater treatment process. Accurate monitoring of this can benefit process efficiency and cost savings.

In the primary and secondary sedimentation stages, sewage flows through large clarifiers or settlement tanks. The primary tank settles sludge by allowing grease and oils to rise to the surface where they are skimmed off. A rotating bridge moves around the tank slowly to scrape off unwanted floating particles. The heavier sludge suspended in the wastewater will settle at the bottom of the settlement tank.

The point where this separation occurs is called the sludge blanket. In secondary clarifiers/tanks, microorganisms digest the organic matter in the wastewater, creating the sludge floc, which will settle at the bottom of the tank.

Sludge level measurement measures the distance between the sludge blanket and the water level at the top of the tank. Once the sludge has reached the required density in the primary settlement tank, the controller will switch on the pumps and pump the sludge into digestors. The sludge will then be prepared for the secondary treatment stage.

Many control factors ensure a well-performing system in the secondary stage, but the sludge blanket level is essential.

Once the sludge has been utilised to its full potential in the primary and secondary stages, it becomes waste sludge. It undergoes further treatment, often via anaerobic digestion, thickening, dewatering, composting, and land application as a fertiliser.

Why measure the sludge blanket level? 

Monitoring the sludge blanket level has many benefits. They include capital saving costs and reducing carbon footprints.

Effective sludge level measurement helps municipal and industrial treatment plants generate electricity. Many large sewage treatment plants work to burn the gas produced in digestors to drive turbines that generate electricity. Producing more gas means more electricity can be generated. One of the most critical factors determining gas volume is the quality and density of the sludge delivered to the digestors.

Operators can ensure that sludge extraction pumps are used efficiently. Excess, or poorly settled sludge, should not wash out into wastewater effluent paths. This can prevent overspills and regulation breaches.

Other sludge handling processes, such as thickeners and dewatering equipment, perform better when fed with a higher concentration of sludge. The diluted and lower concentration sludge will require increased dosing, digestor heating, and pumping costs.

On top of plant and operation savings, it also allows companies to save on the labour costs of manual sampling. This means that there is a wealth of feedback instantly available, allowing for overall greater system control for plant managers and wastewater engineers worldwide.

How to achieve an effective sludge blanket level measurement? 

The Pulsar Measurement Sludge Finder 2 is a versatile, accurate, and reliable solution to measuring interface levels in primary or secondary settlement tasks and uses echo processing algorithms to identify the sludge interface level. The Viper transducer operates ultrasonically through the wastewater by measuring the distance between the sludge blanket surface.

Traditionally, manual sludge blanket level measurement techniques required engineers and operators to be exposed to wastewater and sludge for a long time. These techniques were labour-intensive and time-consuming. It also presented health and safety issues with personnel exposed to hazardous substances.

Automating this process with non-contact sludge level measurement eliminates these issues. It allows staff to see real-time sludge blanket echo graphs on screen without going near the materials. It pairs with Pulsar Measurement’s echo processing algorithms to identify the sludge interface level. The Viper transducer keeps the transducer face clean and debris-free with a built-in external wiper blade. That eliminates the need for downtime and maintenance of a submersible sensor.

This sludge blanket level system can help municipal or industrial treatment plants ensure their complete treatment process runs efficiently. It can generate electricity and ensure that excess sludge is not pumped into local water sources. It also aids with health and safety compliance as well as environmental regulations.

The Sludge Finder 2 is used in thousands of applications worldwide and offers different options depending on the application requirements. It includes single or dual sensor inputs, installation accessories, communication outputs, and a PC Software Suite that offers Sludge Finder 2 software that can be used to record and save the parameters from sludge blanket-level measurement applications.

A case study of the Sludge Finder 2

Beijing Ben-Hua (BBH), Pulsar Measurement distributors in China, were approached by Taihe Sewage Treatment Plant (Taihe) in Shanghai for help with sludge level measurement in one of its sedimentation tanks. Taihe required accurate and reliable sensors to monitor sludge level as it is one of the plant’s control system parameters. Floc is always present in the tank and could not be monitored accurately with the existing sludge level sensor.

As Taihe could not accurately measure the sludge blanket, they contacted BBH for help. BBH went to Taihe’s site and conducted a trial with the Pulsar Measurement Sludge Finder 2 (SF2) and Viper Transducer. During the trial, the readings from the Sludge Finder 2 were cross-checked and verified with a high-resolution underwater camera. There was a good correlation between the SF2 readings and manual level measurement via the underwater camera.

As a result of the trial, Taihe got the accurate and reliable readings they were looking for and was satisfied with the product. It decided to replace the existing measurement unit with the SF2. Commenting on the application, a representative from BBH said, “We are glad the customer is satisfied with the trial as it provides the accurate and reliable data that they are looking for.”

To find out more, go to the Pulsar Measurement website.

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