Chain Scraper System

For sludge and scum collection and removal we offer chain & flight-type chain scraper systems. These are the most sophisticated systems for sludge and scum removal from rectangular settling tanks. Chain Scraper Systems can be used in multiple application basin types. 

View our 4-shaft Chain Scraper System in 3D

DEWA 4-shaft Chain Scraper System for top scum and bottom sludge scraping

Globally tested and proven quality

Our systems are trusted and used by municipal and industrial customers worldwide from small private companies to leading international contractors. 

  • We have nearly 40 years of experience in this field as the company was founded in 1986
  • We have delivered close to 4000 chain scraper systems
  • Deliveries in all five continents and almost 90 countries

Highly flexible solution for a wide range of applications

We offer all possible configurations for rectangular basins from top and bottom scraping to multi-layer systems and all the needed accessories for these systems including scum pipes, beach plates and system controls.

Two shaft Chain Scraper System for top scum scraping.

Key features

DEWA Chain scraper systems offer unbeatable advantages over the other available systems

  • Efficient footprint compared to circular basins
  • Easy to install
  • Low energy consumption
  • Can be built on top of each other
  • High removal efficiency
  • Low wearing rate
  • Low maintenance cost
  • Long life span
  • Lightweight
  • Durable and non-corrosive components

Our superior design and DEWA components offer top-class features, performance, and durability

1. DEWA Scraper Flight

  • Composite (GRP) scraper flights are extremely durable and lightweight
  • Available in various models for different applications. 
  • Sludge does not accumulate inside the c-channel flight and maintenance is easy even after years and decades of use. 
  • High-grade wear shoes and rubber materials are selected according to the type of application. 
  • Additional features such as brushes can be installed on the scraper flights as needed.
  • Installation of the flight is very easy and there are no limitations for the placement of the flights. 

2. Collector Chain

  • LK-160 is available with three strengths (ST, MD, HD), selected according to the clarifier type and size. 
  • DEWA chain design has distinctive advantages, as the spacer sleeve rotates over the sprockets (same principle as in bicycle chain). This design feature maximizes the life span of the collector chain and the sprockets as the wear is minimal. 
  • All pins carry the load of the chain when in contact with the sprocket and there is no risk of overjumping (no need for an overjumping protection device).

3. Shaft assembly

  • All shafts (head shafts, tensioning, idler stubs), collars, and wall brackets are made of high-grade steel materials (AISI304, AISI316, Super Duplex)
  • Designed for heavy sludge loads. 
  • Shaft sprockets can be turned around, which doubles the life span of the sprockets. 
  • All bearings are lubrication-free and won’t require regular maintenance.

4. Drive assembly

  • The Dewa chain scraper system is run by an electric motor and gear that are selected according to the application and required speed with extremely low energy consumption (typical drives vary from 0,12 kW to 0,37 kW). 
  • Sprockets and drive chains are selected according to the application.
  •  The drive unit is protected with an easily removable cover. 
  • The running of the system is monitored by electrical torque-sensing against under or overload.

5. Carry, return and bottom rails

  • All carry and return rails including wall brackets are made of superior stainless steel materials. 
  • This allows smooth sliding and low friction with DEWA wear shoe parts and a practically infinite lifetime.

6. Tensioning Shaft Assembly and Collector Chain Tensioning Device

  • A unique collector chain tensioning system allows chain tensioning without draining the tank and adjusting can be done while the system is running. 
  • This feature saves time and resources and is the most operator-friendly solution. 
  • The system prevents misalignment faults which are caused by loose chains. 
  • The system can be equipped with an automatic tensioner and sensor indicators that are especially convenient when the sludge collector is totally under the water and is not visible to the operator

7. Parallel Run Control System

  • A safety system that monitors the alignment of the scraper flights. 
  • The system will stop the chain scraper system if the scraper flights are not aligned correctly to avoid any possible damage or additional damage to the system.

8. Floating Scum Removal Pipe

  • For floating surface scum removal, we offer an effective “scum pipe”. 
  • Can be equipped with a manual or electrical turning actuator
  • Size (typically from DN250 to DN400), rotating degree and technology can be selected according to the water level variation. 
  • We also deliver additional weirs and channels as needed.

DEWA Chain Scraper System configuration matrix

A DEWA Chain Scraper System (CSS) is always customized and manufactured by our specialists to our customers’ needs. This process is based on the material, construction and dimensional needs of the certain application and type of basin. This matrix will help you to observe some of the key factors behind the final composition of a chain scraper system.

Type of applicationType of basinType of scraperSteel materialBasin dimensions and quantityOther features & accessories
Waste water treatment

Water treatment / drinking water


API oil-water separation

Storm water

Other industrial solutions

Primary settling

Secondary settling


Lamella tank

Multi layer

Sand trap

Grease skimmer
4-shaft top and bottom scraping

2-shaft top scraping

2-shaft bottom scraping

3-shaft bottom scraping

Special combinations
Stainless steel AISI304

Stainless steel AISI316

Super Duplex



Number of basins
System controls

Scum pipes

Beach plates 



Let’s start a project together!

We provide equipment and services globally. Our systems are used in over 90 countries. Contact our sales team and let’s go to work!