Sedimentation Processes
Sedimentation is one of several methods for application prior to filtration: other options include dissolved air flotation and some methods of filtration. Generically, such solids-liquid separation processes are sometimes referred to as clarification processes. There is a variety of methods for applying sedimentation and include: horizontal flow, radial flow, inclined plate, ballasted floc and floc blanket sedimentation.
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.
Sustainability in Water Supply
This article serves as a general reference for sustainable water supply systems. The scope remains global and macroscopic, though there may be regional differences depending on the water sources available in a particular setting. What is considered “sustainable” in one location may be a challenge to sustainability elsewhere.
Simple Options to Remove Turbidity
The health consequences of inadequate water and sanitation services include an estimated 4 billion cases of diarrhea and 1.9 million deaths each year, mostly among young children in developing countries. Diarrheal diseases lead to decreased food intake and nutrient absorption, malnutrition, reduced resistance to infection, and impaired physical growth and cognitive development. Since 1996, a large body of published work has proven the effectiveness of interventions to improve water quality through household water treatment and safe storage (HWTS) at reducing diarrheal disease. However, not all of these interventions remove the turbidity that causes water to look dirty. Although the following options are not proven to reduce diarrheal disease incidence on their own, they can be used to pre-treat water to reduce turbidity before the use of household water treatment products. These options mechanically (through filtration) or chemically (through flocculation and settling of suspended material) remove particles and reduce turbidity. These pre-treatment methods may also increase the efficacy of household water treatment products by removing contaminants that interfere with disinfection and physical filtration processes.
The Impact of Privatisation on the Sustainability of Water Resources
This research investigates potential contributions by the privatization of water production to sustainability of water supply. The main objective is to examine the perceptions of stakeholders concerning privatization as a water governance model and its contribution to water sustainability.
This research provides a robust reference for future planning in the water sector, hinting at the importance of considering public-private partnerships at the federal level as an appropriate model for water sustainability.
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
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.
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.
Filtration Processes
Filtration is a process that removes particles from suspension in water. Removal takes place by a number of mechanisms that include straining, flocculation, sedimentation and surface capture. Filters can be categorised by the main method of capture, i.e. exclusion of particles at the surface of the filter media i.e. straining, or deposition within the media i.e. in-depth filtration.