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Water Treatment Encyclopedia

  • Activated Carbon Filters

    Filtration Theory:For thousands of years filtration has been used to reduce the level of dirt, rust, suspended matter and other impurities from water. This is achieved by passing the dirty input water (influent) through a filter media. As the water passes through the media, the impurities are held in the filter media material. Depending on the impurity impurities and the media, several different physical and chemical mechanisms are active in removing are responsible for the removal of impurities from the water. Some of the equipment used to employ these mechanisms has have changed dramatically over time.The fundamental physical and chemical mechanisms that occur during filtration have become better understood over the years. These advances have allowed water treatment specialists to optimize the removal of impurities from the water. Filtration systems remove particulate matter and, because of the large surface area of filter media, they also can be used to drive chemical reactions that result in the removal of several contaminants. Adsorption Principles: “Adsorption” is one of the most frequently used but least understood terms in discussions of filtration. Adsorption refers to the removal of an impurity from a liquid to the surface of a solid. A water-born, suspended particle adheres…
  • Activated Sludge Process

    Activated sludge process is a process for treating sewage and waste water commonly referred as effluent using bacteria (to degrade the biodegradable organics) and air (Oxygen for respiration). Activated sludge refers to a mixture of microorganisms and suspended solids. The bacterial culture is cultivated in the treatment process to break down organic matter into carbon dioxide, water, and other inorganic compounds. The typical activated sludge process has following basic components: 1) Primary Clarifier to separate the solids carried along with Sewage/Effluent 2) A reactor in which the microorganisms are kept in suspension, aerated, and in contact with the waste they are treating 3) liquid-solid separation; and 4) a sludge recycling system for returning activated sludge back to the beginning of the process. There are many variants of activated sludge processes, including variations in the aeration method and the way the sludge is returned to the process. Activated sludge process offers efficient removal of BOD, COD and nutrients when designed professionally and operated properly. The process itself has flexibility and numerous modifications can be tailored to meet specific requirements (e.g. for nitrogen removal). It is a complex mix of microbiology and biochemistry involving many different sorts of microbes. In the Activated Sludge Plant (ASP) bacteria…
  • Advanced Oxidation Processes

    Advanced oxidation processes (abbreviation: AOPs), in a broad sense, refers to a set of chemical treatment procedures designed to remove organic (and sometimes inorganic) materials in water and waste water by oxidation through reactions with hydroxyl radicals (·OH). In real-world applications of wastewater treatment, however, this term usually refers more specifically to a subset of such chemical processes that employ ozone (O3), hydrogen peroxide (H2O2) and/or UV light. One such type of process is called in situ chemical oxidation. AOPs rely on in-situ production of highly reactive hydroxyl radicals (·OH). These reactive species are the strongest oxidants that can be applied in water and can virtually oxidize any compound present in the water matrix, often at a diffusion controlled reaction speed. Consequently, ·OH reacts unselectively once formed and contaminants will be quickly and efficiently fragmented and converted into small inorganic molecules. Hydroxyl radicals are produced with the help of one or more primary oxidants (e.g. ozone, hydrogen peroxide, oxygen) and/or energy sources (e.g. ultraviolet light) or catalysts (e.g. titanium dioxide). Precise, pre-programmed dosages, sequences and combinations of these reagents are applied in order to obtain a maximum •OH yield. In general, when applied in properly tuned conditions, AOPs can reduce…
  • Advantages of Nanofiltration

    There are many advantages of nanofiltration. Here's a brief rundown of them. Nanofiltration is a relatively recent membrane process used most often with low total dissolved solids water such as surface water and fresh groundwater, with the purpose of softening (polyvalent cation removal) and removal of disinfection by-product precursors such as natural organic matter and synthetic organic matter. Nanofiltration (NF) is one of the four membrane technologies, which utilize pressure to effect separation of contaminants from water streams. The other three are microfiltration, ultrafiltration and reverse osmosis (RO). All of these technologies utilize semi-permeable membranes that have the ability to hold back (reject) dissolved and/or suspended solids from a water stream containing these contaminants. Nanofiltration is also becoming more widely used in food processing applications such as dairy for simultaneous concentration and partial (monovalent ion) demineralization. This mechanism depends upon the valence of the salt ion in question. Recognize that a salt is a compound of two or more ions with an electronic charge. Valence is the number of charges on the ions that form the specific salt, which is not always sodium chloride (NaCl); sodium and chloride are monovalent ions because they have only one charge, whereas ions such…
  • Aerobic Treatment Package

    Aerobic Treatment Packages for Untreated Water Definitions: Wastewater : water polluted by a mixture of all sorts of inorganic (sand, clay, salts) and organic (proteins, sugars, oils and fats) components;Some of them appear in dissolved form and other in suspended form; Origins: Industrial, Agricultural, or municipal origin. Wastewater Treatment : the process that removes the majority of the contaminants from wastewater or sewage and produces both a liquid effluent suitable for disposal to the natural environment and a sludge. Treatment Methods : Combination of mechanical, physicochemical & biological treatment steps. Biological Wastewater Treatment: Collective name for the processes that eliminate the organic matter using micro-organisms. Nutrients such as N (nitrogen) and P (phosphorus) can also be removed, thereby reducing the eutrophication risk. Biological treatment is actually the accelerated version of nature’s own way of water cleaning. It produces a clear effluent, harmless for the environment, by removing organic compounds from the wastewater, as well as nutrients such as N and P. From the economical point of view biolo­gical treatment is the most feasible method.AES Arabia Ltd systems are an advanced evolution of the most common biological treatment method, using activated sludge. Activated sludge: A variable and mixed community of microorganisms in an aerobic aquatic environment. These…

Case Studies

The Impact of Ferrous Ion Oxidation on Silica Scaling in RO Systems

Controlling Aluminum Silicate Formation in Membrane Separation Processes

An Evaluation of Corrosion Control Additives for Potable RO Permeate

A Relationship Between Phosphate Scales and Silica Fouling in WasteWater RO Membrane Systems

Excessive Sulfuric Acid Dosing Resulting in Irreversible Scale Formation

Optimizing Scale Inhibition Costs in Reverse Osmosis Desalination Plants