Author insight: "From biofilm ecology to reactors: a focused review"

Water Science and Technology article "From biofilm ecology to reactors: a focused review" has been made Open Access for a limited time. One of its authors, Distinguished IWA Fellow and professor of Civil and Environmental Engineering Glen Daigger, shares his thoughts on the paper and why its content is valuable for the water community.

What needs to change to achieve access to sanitation for all by 2030? What needs to change to achieve access to sanitation for all by 2030?

Andrés Hueso, Senior Policy Analyst for Sanitation at WaterAid, discusses the opportunities and challenges involved in global prioritisation of sanitation and water for all.

Author interview: Michiel Tukker

Michiel Tukker, co-author of the recently published Hydraulic Design and Management of Wastewater Transport Systems, offers insight into his new book, his research and a new project in partnership with Delft University.

A new approach for studying the operation of a secondary sedimentation tank (SST)

Lucio Pezza, expert on the management, control and maintenance of water and wastewater treatment plants, covers some key concerns of his new article on the operation of secondary sedimentation  tanks (SSTs).

Coagulation and Flocculation in Water and Wastewater Treatment

Coagulation and flocculation are an essential part of drinking water treatment as well as wastewater treatment. This article provides an overview of the processes and looks at the latest thinking.

Up Flow - Anaerobic Sludge Blanket Reactor (UASB)

Up flow anaerobic sludge blanket technology also known as UASB reactor is a form of anaerobic digester which used in wastewater treatment. UASB reactor is a methane-producing digester, which uses an anaerobicprocess and forming a blanket of granular sludge and is processed by the anaerobic microorganisms.

Industrial Wastewater Treatment

Industrial wastewater treatment covers the mechanisms and processes used to treat waters that have been contaminated in some way by anthropogenic industrial or commercial activities prior to its release into the environment or its re-use.

Most industries produce some wet waste although recent trends in the developed world have been to minimise such production or recycle such waste within the production process. However, many industries remain dependent on processes that produce wastewaters.

Physico-chemical Water Treatment Processes

Physico-chemical treatment of wastewater focuses primarily on the separation of colloidal particles. This is achieved through the addition of chemicals (called coagulants and flocculants). These change the physical state of the colloids allowing them to remain in an indefinitely stable form and therefore form into particles or flocs with settling properties (3, 4 and 5).


Flocculation is a process which clarifies the water. Clarifying means removing any turbidity or colour so that the water is clear and colourless. Clarification is done by causing a precipitate to form in the water which can be removed using simple physical methods. Initially the precipitate forms as very small particles but as the water is gently stirred, these particles stick together to form bigger particles - this process is sometimes called flocculation. Many of the small particles that were originally present in the raw water adsorb onto the surface of these small precipitate particles and so get incorporated into the larger particles that coagulation produces. In this way the coagulated precipitate takes most of the suspended matter out of the water and is then filtered off, generally by passing the mixture through a coarse sand filter or sometimes through a mixture of sand and granulated anthracite (high carbon and low volatiles coal).

Sludge Production

Commonly sludge refers to the residual, semi-solid material left from industrial wastewater, or sewage treatment processes.


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