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.
Sludge Drying Overview - Treatment Methods and Applications
Sludge is a residual, semi-solid by-product left from industrial or refining processes. It is a separated solid suspended in a liquid, typically containing major quantities of interstitial water between its solid particles. This material can be dried to cut its volume and reduce most of the moisture content of the biosolids present in the sludge.
Helminth eggs are the infective agents for the types of worm diseases known globally as helminthiases. Although helminths are pluricellular animals their eggs are microscopic (around 20 to 80 μm for those that are important in the sanitary field) and are contained in variable amounts in wastewater, sludge and excreta. Helminth eggs infect humans through: (1) the ingestion of food crops polluted with wastewater sludge or excreta, (2) direct contact with polluted sludge or faecal material, and (3) the ingestion of polluted meat or fish.
Bio-toilets: Sustainable Solution to India’s Sanitation Challenge
Banka BioLoo Pvt Ltd, a firm committed to environmental betterment and social uplift, is supporting to eradicate the malaise of open defecation in India. By providing eco-friendly bio-toilets (or bioloos), the enterprise is helping meet the Millennium Development Goals (MDG-7) and actively supporting the government’s vision of an open defecation free society.
Removal Technologies in Wastewater Treatment
Since heavy metal ions are non-biodegradable, they can accumulate their amounts along the food chain. Therefore, it is critical necessary to remove or minimize the heavy metal ions in wastewater systematically. In this article, we mainly introduce three commonly used methods for heavy metal elimination: chemical precipitation, ion exchange, and adsorption.