Settling is the process by which particulates move towards the bottom of a liquid and form a sediment. Particles that experience a force, either due to gravity or due to centrifugal motion will tend to move in a uniform manner in the direction exerted by that force. For gravity settling, this means that the particles will tend to fall to the bottom of the vessel, forming sludge or slurry at the vessel base. Settling is an important operation in many applications, such as mining, wastewater and drinking water treatment, biological science, space propellant reignition, and scooping.
Turbidity is the cloudiness or haziness of a fluid caused by large numbers of individual particles that are generally invisible to the naked eye, similar to smoke in air. The measurement of turbidity is a key test of both water clarity and water quality.
Water quality refers to the chemical, physical, and biological characteristics of water based on the standards of its usage. It is most frequently used by reference to a set of standards against which compliance, generally achieved through treatment of the water, can be assessed. The most common standards used to monitor and assess water quality convey the health of ecosystems, safety of human contact, extent of water pollution and condition of drinking water. Water quality has a significant impact on water supply and often determines supply options.
In chemistry, a suspension is a heterogeneous mixture of a fluid that contains solid particles sufficiently large for sedimentation. The particles may be visible to the naked eye, usually must be larger than one micrometer, and will eventually settle, although the mixture is only classified as a suspension when and while the particles have not settled out.
Biochemical oxygen demand is an analytical parameter representing the amount of dissolved oxygen (DO) consumed by aerobic bacteria growing on the organic material present in a water sample at a specific temperature over a specific time period. The BOD value is most commonly expressed in milligrams of oxygen consumed per liter of sample during 5 days of incubation at 20 °C and is often used as a surrogate of the degree of organic water pollution.
Total suspended solids (TSS) is the dry-weight of suspended particles, that are not dissolved, in a sample of water that can be trapped by a filter that is analyzed using a filtration apparatus known as sintered glass crucible. TSS is a water quality parameter used to assess the quality of a specimen of any type of water or water body, ocean water for example, or wastewater after treatment in a wastewater treatment plant. It is listed as a conventional pollutant in the U.S. Clean Water Act. Total dissolved solids is another parameter acquired through a separate analysis which is also used to determine water quality based on the total substances that are fully dissolved within the water, rather than undissolved suspended particles.
Total organic carbon (TOC) is an analytical parameter representing the concentration of organic carbon in a sample. TOC determinations are made in a variety of application areas. For example, TOC may be used as a non-specific indicator of water quality, or TOC of source rock may be used as one factor in evaluating a petroleum play. For marine surface sediments average TOC content is 0.5% in the deep ocean, and 2% along the eastern margins.
Coal analysis techniques are specific analytical methods designed to measure the particular physical and chemical properties of coals. These methods are used primarily to determine the suitability of coal for coking, power generation or for iron ore smelting in the manufacture of steel.
Total dissolved solids (TDS) is a measure of the dissolved combined content of all inorganic and organic substances present in a liquid in molecular, ionized, or micro-granular suspended form. TDS are often measured in parts per million (ppm). TDS in water can be measured using a digital meter.
Suspended solids refers to small solid particles which remain in suspension in water as a colloid or due to motion of the water. Suspended solids can be removed by sedimentation if their size or density is comparatively large, or by filtration. It is used as one indicator of water quality and of the strength of sewage, or wastewater in general. It is an important design parameter for sewage treatment processes.
Loss on ignition (LOI) is a test used in inorganic analytical chemistry and soil science, particularly in the analysis of minerals and the chemical makeup of soil. It consists of strongly heating ("igniting") a sample of the material at a specified temperature, allowing volatile substances to escape, until its mass ceases to change. This may be done in air or in some other reactive or inert atmosphere. The simple test typically consists of placing a few grams of the material in a tared, pre-ignited crucible and determining its mass, placing it in a temperature-controlled furnace for a set time, cooling it in a controlled atmosphere, and re-determining the mass. The process may be repeated to show that the mass change is complete. A variant of the test in which mass change is continually monitored as the temperature changes is called thermogravimetry.
Reid vapor pressure (RVP) is a common measure of the volatility of gasoline and other petroleum products. It is defined as the absolute vapor pressure exerted by the vapor of the liquid and any dissolved gases/moisture at 37.8 °C (100 °F) as determined by the test method ASTM-D-323, which was first developed in 1930 and has been revised several times. The test method measures the vapor pressure of gasoline, volatile crude oil, jet fuels, naphtha, and other volatile petroleum products but is not applicable for liquefied petroleum gases. ASTM D323-15a requires that the sample be chilled to 0 to 1 degrees Celsius and then poured into the apparatus; for any material that solidifies at this temperature, this step cannot be performed. RVP is commonly reported in kilopascals (kPa) or pounds per square inch (psi) and represents volatization at atmospheric pressure because ASTM-D-323 measures the gauge pressure of the sample in a non-evacuated chamber.
Sewage is a type of wastewater that is produced by a community of people. It is typically transported through a sewer system. Sewage consists of wastewater discharged from residences and from commercial, institutional and public facilities that exist in the locality. Sub-types of sewage are greywater and blackwater. Sewage also contains soaps and detergents. Food waste may be present from dishwashing, and food quantities may be increased where garbage disposal units are used. In regions where toilet paper is used rather than bidets, that paper is also added to the sewage. Sewage contains macro-pollutants and micro-pollutants, and may also incorporate some municipal solid waste and pollutants from industrial wastewater.
Basic sediment and water (BS&W) is both a technical specification of certain impurities in crude oil and the method for measuring it. When extracted from an oil reservoir, the crude oil will contain some amount of water and suspended solids from the reservoir formation. The particulate matter is known as sediment or mud. The water content can vary greatly from field to field. It may be present in large quantities for older fields, or if oil extraction is enhanced using water injection technology. The bulk of the water and sediment is usually separated at the field to minimize the quantity that needs to be transported further. The residual content of these unwanted impurities is measured as BS&W. Oil refineries may either buy crude to a certain BS&W specification or may alternatively have initial crude oil dehydration and desalting process units that reduce the BS&W to acceptable limits, or a combination thereof.
Water chemistry analyses are carried out to identify and quantify the chemical components and properties of water samples. The type and sensitivity of the analysis depends on the purpose of the analysis and the anticipated use of the water. Chemical water analysis is carried out on water used in industrial processes, on waste-water stream, on rivers and stream, on rainfall and on the sea. In all cases the results of the analysis provides information that can be used to make decisions or to provide re-assurance that conditions are as expected. The analytical parameters selected are chosen to be appropriate for the decision-making process or to establish acceptable normality. Water chemistry analysis is often the groundwork of studies of water quality, pollution, hydrology and geothermal waters. Analytical methods routinely used can detect and measure all the natural elements and their inorganic compounds and a very wide range of organic chemical species using methods such as gas chromatography and mass spectrometry. In water treatment plants producing drinking water and in some industrial processes using products with distinctive taste and odors, specialized organoleptic methods may be used to detect smells at very low concentrations.
Mixed liquor suspended solids (MLSS) is the concentration of suspended solids, in an aeration tank during the activated sludge process, which occurs during the treatment of waste water. The units MLSS is primarily measured in milligram per litre (mg/L), but for activated sludge its mostly measured in gram per litre [g/L] which is equal to kilogram per cubic metre [kg/m3]. Mixed liquor is a combination of raw or unsettled wastewater or pre-settled wastewater and activated sludge within an aeration tank. MLSS consists mostly of microorganisms and non-biodegradable suspended matter. MLSS is an important part of the activated sludge process to ensure that there is a sufficient quantity of active biomass available to consume the applied quantity of organic pollutant at any time. This is known as the food to microorganism ratio, more commonly notated as the F/M ratio. By maintaining this ratio at the appropriate level the biomass will consume high percentages of the food. This minimizes the loss of residual food in the treated effluent. In simple terms, the more the biomass consumes the lower the biochemical oxygen demand (BOD) will be in the discharge. It is important that MLSS removes COD and BOD in order to purify water for clean surface waters, and subsequently clean drinking water and hygiene. Raw sewage enters in the water treatment process with a concentration of sometimes several hundred mg/L of BOD. Upon being treated by screening, pre-settling, activated sludge processes or other methods of treatment, the concentration of BOD in water can be lowered to less than 2 mg/L, which is considered to be clean, safe to discharge to surface waters or to reuse water.
Simultaneously extracted metals/Acid-volatile sulfide (SEM-AVS) is an approach used in the field of aquatic toxicology to assess the potential for metal ions found in sediment to cause toxic effects in organisms dwelling in the sediment. In this approach, the amounts of several heavy metals in a sediment sample are measured in a laboratory; at the same time, the amount of acid-volatile sulfide is determined. Based on the chemical interactions between heavy metals (SEM) and acid-volatile sulfide (AVS), the concentrations of these two components can be used to assess the potential for toxicity to sediment-dwelling organisms.
Sludge is a semi-solid slurry that can be produced from a range of industrial processes, from water treatment, wastewater treatment or on-site sanitation systems. It can be produced as a settled suspension obtained from conventional drinking water treatment, as sewage sludge from wastewater treatment processes or as fecal sludge from pit latrines and septic tanks. The term is also sometimes used as a generic term for solids separated from suspension in a liquid; this soupy material usually contains significant quantities of interstitial water. Sludge can consist of a variety of particles, such as animal manure.
Total carbon (TC) is an analytical parameter representing the concentration of carbon in a sample. TC includes carbon in any form, whether organic or inorganic, volatile or fixed, dissolved or suspended. In many application areas, rather than TC, a parameter representing of subset of TC is measured; examples include Total organic carbon (TOC), Particulate inorganic carbon (PIC), and Dissolved organic carbon (DOC).
