Dexter Watson

Equipment for the wet waste industry


Here are the answers to our most frequently asked questions;

Q: What is sludge / wastewater dewatering?

A: Sludge / wastewater dewatering is a process where the water and solid fractions are separated by filtration aided by a flocculant.


Q: What is filtrate?

A: Filtrate is the water fraction produced by the dewatering process.


Q: What is a cake?

A: Cake is a term used to describe the flocculated solid fraction of the dewatering process once the water fraction “filtrate” has been drained, the flocculated solids then forms a “cake”.


Q: What is sludge thickening?

A: Sludge thickening is where the dewatering process is halted before a cake is formed, reducing the overall amount of waste product having to be tankered away for disposal i.e. reducing several loads down to one.


Q: What is polymer?

A: Polymer or Polyacrylamide to give its correct title, is a flocculant and is made up of chains of molecules that carry either a negative (anionic) or positive (cationic) charge which attracts the opposite charge found in sludges and wastewater causing flocculation (separating the solid and water fractions). By using a flocculant greatly speeds up the dewatering process and produces a cake quickly.


Q: What is sludge?

A: Sludge is a term to describe a viscous mixture of liquid and solid components that is produced from several sources as found in naturally occurring mud and silts. Industrial processes, such as refinery, mining, and quarrying activities etc. Commercial activities, as in forecourt interceptors, car washes, tannery, and abattoirs. Domestic sludges, wastewater treatment, septic tanks, and grease traps etc. The list is endless, if its runny and dirty it’s a sludge.


Q: What is a typical sludge processing time?

A: Processing times can vary depending on the sludge being treated, normally the more fibrous the sludge the quicker the dewatering processing time, it is also dependent on the sludges dry solids content (D/S). Average time to produce a cake normally takes between 6 to 18 hours, however the longer you leave the cake to stand the drier it gets.


Q: What equipment do I need to dewater with?

A: The equipment we produce is the Dexter Watson Dewatering / Sludge thickening Container (DWC) along with  a Polymer Dosing Unit (PDU). If the waste stream requires screening a Coarse Screening Container (CSC) is added to the process to remove any crude debris such as rags, broken pipework etc. The CSC is also used to bulk up the sludge / wastewater prior to the dewatering process.


Q: What benefits and cost savings can I expect by dewatering?

A: Benefits: Being mobile, the Dexter Watson dewatering system is easily moved and placed centrally to any operational area saving on wasted mileage, time, maintenance and fuel costs. The system also gives an operator the ability to be more reactive to customer demands and increases productivity leading to greater profits.

The system provides a 24/7 facility, improving working practices by eliminating standing loads and the reliance on WWTW gate opening/closing times, providing better time management, forward planning, and more control over resources. By dewatering you greatly reduce the amount of waste needing to be transported resulting in substantial savings on disposal costs.


Q: What service does Dexter Watson provide? 

A: Our staff have over 30 years knowledge and experience working in the wet waste industry and have completed a wide range of projects across many industries including working with companies who have council contracts. We have the luxury of sharing facilities with a long established fabrication company who operate state of the art equipment including; CNC plasma and laser profiling, CNC press brake and robotic welding equipment. We work with a vast range of materials from mild and stainless steel, aluminium and plastics. This puts us in the perfect position to offer a full design and manufacture service to cater for individual needs here in the UK. Services include everything from sludge and wastewater testing, design and manufacture of equipment  right through to onsite operator training.

If you have anymore questions please get in touch via 01904 735346 or