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).
Commonly sludge refers to the residual, semi-solid material left from industrial wastewater, or sewage treatment processes.
Sequencing Batch Reactor
Sequencing batch reactors (SBR) or sequential batch reactors are industrial processing tanks for the treatment of wastewater. SBR reactors treat waste water such as sewage or output from anaerobic digesters or mechanical biological treatment facilities in batches. Oxygen is bubbled through the waste water to reduce biochemical oxygen demand (BOD) and chemical oxygen demand (COD) to make suitable for discharge into sewers or for use on land. While there are several configurations of SBRs the basic process is similar.
Water and Wastewater Management Projects in the Tropics
Over the last 30 years a significant number of water and sanitation projects have been implemented in developing countries and billions of dollars has been spendt. Projects have covered rural as well as urban water supply systems, wastewater collection, disposal and treatment systems, and have mainly been financed by international funding agencies such as international banks and international aid organisations. However, unfortunately it is a fact that the number of failures, or non-functioning, of the established systems, outnumbers the number of successes.
Reduction of Sludge Production in Wastewater Treatment Plants
The volume of sludge produced in a WWTP is only about 1% (dewatered sludge is 0.5‰) of the volume of influent wastewater to be treated. To manage WWTPs effectively and efficiently, it is absolutely necessary to extract waste sludge, including inert solids and excess biomass, in order to prevent their accumulation within the system.