Best-in-Class Mechanical Dewatering Methods
Depending on what industry you’re in the term “dewatering” can mean different things. Construction site dewatering typically refers to the management of water on a site, whether it be pond water or ground water to allow construction activities to continue uninhibited. In this context dewatering typically focuses on the removal of water from the site through pumping and its corresponding treatment and discharge.
In contrast wastewater dewatering typically focuses on slurry liquid solid separation to reduce waste volumes and provide waste management options. The wastewater dewatering process is one step in the operation of a wastewater treatment system. Optimization of wastewater dewatering then typically involves maximizing throughput, minimizing costs and maximizing separation.
Optimizing the Dewatering Process
Mechanical dewatering is a common method to reduce and manage liquid waste streams. Factors to consider in choosing and optimizing your dewatering process include:
- Polymer dosage
- Equipment maintenance
- Ease of operation
- Sludge Feed
- Effluent characteristic requirements
- Volumes to be processed
- End use
Best-in-Class Mechanical Dewatering Canada Methods
The number of dewatering methods are as varied as the number of liquid waste streams they treat. As one component of a treatment system, variation in implementation is limitless. The three most common methods of wastewater dewatering are centrifuge, belt press and geo-textile bags.
The centrifuge spins the polymerized sludge feed at a high speed to separate the solids and liquid. They have a high power requirement and polymer dosage rate. They benefit from a smaller foot print, low maintenance and ease of operation when used with a consistent sludge feed. Centrifuge units are common place in many large wastewater treatment facilities and achieve solids concentrations anywhere from 18-30%.
Belt presses come in a variety of designs but all work on the principal of squeezing the polymerized sludge feed to separate the water from the solids. The belt is permeable to water but not solids allowing their separation. They benefit from lower power requirements and dosage rates. They have higher maintenance and require more operational oversight. They work well with consistent sludge feed. Belt presses are common in many small to mid-size wastewater treatment facility and achieve solids concentrations anywhere from 18-28%.
Geo-textile bags provide a unique dewatering option. They work by trapping the solids inside the bag and allowing the water to permeate through the geo-textile. This method typically requires a large footprint to setup, although some unit have been setup in a standard waste bin. The bags allow for large volumes to be dewatered quickly and have been used in the past during lagoon clean outs. The bags are a one-time use and once full are disposed of increasing the cost of the operation for larger steady sludge feed flows. They are able to handle fluctuations in solids content rather well and benefit from lower polymer dosage rates. They also can provide storage for the captured solids (which will continue to desiccate) while awaiting final disposal or reuse. Because the dewatered sludge can be left to desiccate for any amount of time this method can achieve solids concentrations anywhere from 18-55%.
Rotary drum dewatering units while used throughout the world are a newer entrant into the dewatering arena and perhaps serve a niche in the market. Wessuc first started using rotary units in 2010 when we used a vacuum unit. Since then we have switched to a rotary fill unit which works in much the same principal as a geo-textile bag. The rotary drum is filled to capacity while the liquid permeates through the outer shell. Once the unit is filled, the material is rotated for a number of hours to expedite the drying process. This method benefits from low polymer usage, low energy requirements and simple operation. The units can handle high solids fluctuations in the sludge feed and produce a high quality effluent (less than 100 mg/L TSS). The higher solids found in a digester clean out project result in dewatered solids concentration of 25-50%.
3 Important Best Practices in Detwatering
1. Testing and Evaluation
Polymer dosage rates will vary greatly depending on the dewatering method being used and the liquid waste characteristics. Liquids with higher solids concentrations will require higher dosage rates. Different dewatering methods will require different dosage rates to achieve equal solids dryness results which related directly to the overall dewatering cost. Polymer cost are often more than 50% of the input cost required for a treatment system and as such require testing and evaluation to determine the optimal type and dosage.
2. Automating Methods
Ease of operation is a key factor in the overall cost of the equipment. The more automated the equipment the less man hours required to supervise, trouble shoot, restart, and clean up the equipment. Therefore, the more a method can be automated, the more time operators can spend optimizing other areas of the wastewater treatment process.
3. Achieving High Quality Effluent
Effluent quality required from the dewatering operation will directly impact the available options. High quality effluent while achievable often requires a slower process with solids higher capture rates. For most wastewater treatment plants, the effluent quality is not the determining factor as it is typically returned to the plant for reprocessing and not directly discharged to the environment.
Wessuc has experience completing projects with each of these best practices and has been working to improve the dewatering process in Canada for over 10 years to achieve efficiency and reduce cost and environmental impact. Contact us for more information on dewatering Canada.
Given the rising costs of energy in our province, it is important that aeration tanks that process waste water run as efficiently as possible. Whether at the municipal or industrial level, it is estimated that electricity typically accounts for about 30% of the cost in wastewater treatment. This article will examine what is needed to ensure that that you are getting the most out of your aeration tank.
Aeration System Components
Essentially aeration systems can be divided into three main parts including: airflow generation, airflow distribution and aeration control. To obtain maximum aeration tank efficiency, each of these parts must be operating at optimal levels.
Types of Blowers
As technology has improved, more efficient types of blowers have been developed. For example, systems that use straight oxygen (O2) require significantly less energy than those that use air. Furthermore, it is essential that the right size and horsepower blowers for the tank be used.
Using multiple blowers is also beneficial because it reduces the chance that a system-wide pumping failure might occur. As old air blowers fail, companies and municipalities may choose to replace them with O2 blowers. While they can be replaced all at once, doing so requires a large amount of capital so it often makes more sense financially to replace them over time to gain greater efficiency.
The piping system is another critical component for helping determine the efficiency of the aeration tank. If the pipes are too small, blowers with more horsepower may be required. If the pipes are too large, the system may become too difficult to control.
Additionally, each of the components of the aeration tanks must meet certain standards to ensure efficiency. These components include air control valves, airflow meters and DO meters.
- Air Control Valves – Valve size should be large enough that they can operate when they are 30-70% open. They should be installed downstream of airflow meters in order to reduce the amount of possible disturbances in the airflow.
- Airflow Meters – There are several different types of airflow meters on the market and all work well as long as they have been properly installed. These must be placed a minimum distance either upstream or downstream of a disturbance. The manufacturer’s guidelines on this distance should be adhered to for optimal efficiency.
- DO Meters – DO Meters have become standard in municipal wastewater plants. These optical-based meters are popular because of their reliable readings and also because they require only a minimal amount of maintenance. These meters should be placed between halfway and two-thirds down the aeration control basin.
Maintenance and Cleaning
Finally, even if you have all the best components, you won’t optimize your efficiency without proper maintenance and regular cleaning. As tanks fill up with sludge, they become less efficient but regular cleaning can help restore them.
The efficiency of an aeration tank comes down to both the components that are used as well as its ongoing maintenance. If you would like to improve the efficiency of your municipal or industrial tank, contact Wessuc today. A member of our team would be happy to meet you for a consultation and discuss possible ways to improve your efficiency.
It frequently amazes our clients how the Wessuc team is able to clean industrial tanks and reservoirs and haul away waste materials using our super vac trucks. There are many benefits however to using vacuum trucks for this purpose.
While there are a variety of types of vacuum trucks and attachments all designed for specific purposes and industries, these vehicles do share certain similarities. They are equipped with high-powered vacuum and hydro-excavation systems which are designed to clean out various types of industrial tanks, lagoons and municipal water infrastructure. These vehicles are also equipped with debris tanks of their own for hauling away materials for safe disposal.
The benefits of vacuum trucks for this purpose are as follows:
There are a variety of makes and models of vacuum trucks on the market today that are equipped for a variety of cleaning jobs for both wet and dry debris. These vehicles can haul away large amounts of hazardous material as they are equipped with water tanks that can hold up to 1,500 gallons and debris tanks that can hold up to 2,000 gallons.
Employing vacuum trucks and experienced crews for cleaning tanks and reservoirs is one of the fastest and safest ways to get the job done. At Wessuc, our crews are fully trained and certified and our equipment is always well maintained and equipped for the job.
Operators undergo extensive training in Confined Space Entry, WHMIS, First Aid, Electrical Awareness, Traffic Protection and more.
The most convenient way to have tanks cleaned is for it to be done onsite by experienced professionals with the right equipment. Our vacuum trucks require minimal water and our technicians are proficient at what they do.
Moving tanks and other equipment around is inconvenient at the best of times, but our fully mobile cleaning units save you the hassle.
Since cleaning can be done onsite, it eliminates many of the costs that would come along with it otherwise. The logistics of each site are assessed ahead of time before the cleaning crew arrives with the super vac truck.
Before their arrival, safety issues are addressed and a plan is developed which in turn mitigates the risk of any unforeseen costs.
Since tanks and other reservoirs are cleaned onsite, that means less downtime for the business or municipality. The amount of time that tanks or vessels are out of operation is reduced as there is no transporting them back and forth. They can be put back into operation as soon as the cleaning process is complete.
Further efficiency is gained by the fact that waste from the industrial tanks is captured directly in the debris tanks of the trucks making it ready for safe transport and disposal.
Whether you operate a business that uses industrial tanks, or whether you work for a municipality and are sourcing service providers to assist you with your cleaning needs and transporting materials, the team at Wessuc can help.
Contact us today for more information.