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.
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).
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.
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.
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.