Glossary
Words That Start With A
| Activated sludge | A treatment technology to remove organic matter by taking advantage of microorganisms in the sludge by dispersing “activated sludge” in which microorganisms are agglomerated under aerobic conditions in sewage. Excess sludge is removed from the septic tank and then treated. |
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| Aeration | In sewage treatment, it is the application or agitation of air to provide oxygen necessary for microorganisms to break down organic matter. Bubbling. |
| Aeration tank | A facility, a tank, where activated sludge and sewage are mixed and aerated to allow microorganisms to decompose organic matter present in the sewage. |
| Aerobic | A condition requiring the presence of or dependent on the presence of oxygen. Aerobic bacteria (microorganisms that grow well in the presence of oxygen). The fermentation rate in this state is fast and odorless. [Related term] Anaerobic |
| Anaerobic | A condition requiring the absence of or not dependent on the presence of oxygen. This condition is used when anaerobic sludge (microorganisms that can grow without oxygen) is digested or methane fermentation is carried out. Fermentation in this state progresses slowly and produces odors (such as hydrogen sulfide). [Related term] Aerobic |
| Anion | A negative ion. Anionic coagulant = negative ion coagulant [Related term] Cation, Nonion |
Words That Start With B
| Biochemical oxygen demand | The amount of oxygen demanded by microorganisms to break down the organic matter present in water. A typical gauge for measuring organic pollution in rivers. It is an indicator that utilizes the fact that the dirtier the water, the more oxygen is demanded by microorganisms. It is an important indicator to calculate the approximate amount of sludge from the amount of BOD in the influent entering the water treatment facility. High BOD levels can lead to a lack of dissolved oxygen. A foul odor is generated when the BOD value is 10 mg/L or higher. [Abbreviations] BOD(Biochemical Oxygen Demand) |
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| Biological treatment | A treatment method to purify sewage by exploiting the ability of microorganisms to break down the organic matter present in the sewage. |
Words That Start With C
| Cation | A positive ion. Cationic coagulant = positive ion coagulant [Related term] Anion, Nonion |
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| Chemical oxygen demand | It is the amount of oxidant consumed when decomposing organic matter in water with an oxidant converted into the amount of oxygen and serves as a gauge to determine how the water is polluted by organic matter. COD tends to be larger than BOD. [Abbreviations] COD(Chemical Oxygen Demand) |
| Chemical precipitation | A method for separating suspended solids and supernatant by adding a coagulant and flocculant if necessary to sewage to increase the diameter of suspended solids, thereby speeding up the settling process. [Related term] Pressure flotation treatment |
| Conventional activated sludge process | A method for treating sewage by injecting air into a mixture of sewage and mud containing microorganisms called activated sludge, which allows the microorganisms to absorb and decompose organic matter present in the sewage. It is also called the conventional process. |
DEF
Words That Start With D
| DAF（Dissolved Air Flotation） | A treatment method in which air is dissolved in water by applying pressure and then solids in the water adhere to fine air bubbles generated by reducing the pressure so that the solids are forced to rise to the surface by buoyancy. The principle is the same as the generation of minute air bubbles the moment you get the lid off a carbonated drink. |
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| Dewatered cake | The residual material of sludge after being dewatered by a dewatering technology. |
| Dissolved air flotation | A treatment method in which air is dissolved in water by applying pressure and then solids in the water adhere to fine air bubbles generated by reducing the pressure so that the solids are forced to rise to the surface by buoyancy. The principle is the same as the generation of minute air bubbles the moment you get the lid off a carbonated drink. [Abbreviations] DAF(Dissolved Air Flotation) [Related term] Coagulation sedimentation method |
| Domestic wastewater | Sewage discharged from home life situations such as toilets, kitchens, baths, laundry, and cooking, excluding industrial wastewater discharged into public water areas (Water Pollution Prevention Act, 1970). Domestic wastewater excluding human waste is called miscellaneous wastewater. Domestic wastewater is becoming a major cause of water pollution such as eutrophication due to nitrogen and phosphorus within the wastewater. It is desirable that sewage treatment facilities be available and that combined septic tanks be widespread in place of flush toilet wastewater purifiers that discharge miscellaneous wastewater untreated. |
Words That Start With F
| Ferric chloride | Ferric chloride. Used as an inorganic coagulant. SUS304 is not corrosion-resistant to ferric chloride and will melt. [Abbreviations] Salt iron |
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| Ferric polysulfate | An inorganic coagulant. It is a reddish-brown liquid with a specific gravity of 1.45. It is much less corrosive than ferric chloride. |
| Fibrous material | They are suspended solids that remain on a standard sieve of 0.075 mm (200 mesh) or 0.15 mm (100 mesh). Along with VTS, this factor influences dewatering performance; the more fibrous material, the lower the water content tends to be. |
| Final clarifier | A facility to allow sludge and treated water generated by biological treatment in a reaction tank to settle out and decompose. The supernatant water is disinfected and then discharged into rivers and the ocean. As it clarifies the water, it is called clarifier. |
GHI
Words That Start With G
| Gravity thickening | A method in which sludge is poured into a tank and allowed to stand still until suspended solids settle out, and then the sediment is collected. It is a method to concentrate sludge by gravity. |
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| Gray water | A water recycling system in which rainwater and wastewater are recycled and reused as toilet flushing water or sprinkling water. Water-saving technologies allow the utilization of limited water resources. It is called gray water because it is between tap water and sewage water. Gray water is reused as toilet flushing water, cooling water, supply water to rivers, canals, and freshwater lakes, water for sprinkling plants, and water for gardens. Reclaimed water purified by sewage treatment is a valuable water resource within the city. |
| Grease trap | An oil interceptor. Commercial kitchens are required to have grease traps. By separating and collecting pollutants such as fats, oils, and garbage contained in wastewater and temporarily holding them in place, grease traps prevent them from flowing directly into the sewerage system. |
Words That Start With H
| Heavy metals | Metals with a specific gravity of 4 to 5 or greater, such as gold, platinum, silver, mercury, chromium, cadmium, lead, and iron, are called heavy metals. Many heavy metals are highly toxic. When ingested repeatedly, even in trace amounts, they accumulate in the body and become harmful to the human body. [Antonym] Light metals: aluminum, etc. |
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Words That Start With I
| Industrial wastes | Waste generated by business activities, including burnt residue, sludge, waste oil, waste acid, and waste alkali, totaling 20 types of waste. |
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| Inverter control | To control the speed of an electric motor utilizing an AC power supply of variable voltage and frequency using a frequency converter. Also referred to as frequency control. |
JKL
Words That Start With L
| Lagoon | A large pond of wastewater left for one day or several months and then used for multiple purposes, including: flow control for maximum sewage flow; sedimentation of sewage as in the normal sedimentation method; making the bottom soil porous for dewatering; completion of chemical treatment solution reaction; biological decomposition of sewage; and natural evaporation. |
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| Lagoon process | This is a type of wastewater treatment process where sewage is detained in a pond for a long period (several days to several dozen days) and purified by sedimentation and microorganisms. Since natural swamps are usually used, this treatment process is less expensive to construct and consumes very little energy compared to terminal sewage treatment plants, but it requires a larger area. |
| Leak | An instance of leaking. For our VOLUTE™ Dewatering Press, it refers to the phenomenon in which the sludge flows outward from the inside of the cylinder. |
MNO
Words That Start With M
| Membrane separation | A sewage treatment technology where a semipermeable membrane or other means is used to physically separate sewage and clean water. It is possible to obtain extremely clean treated water, but at the same time sludge is generated. |
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| Mixed raw sludge | A mixture of primary sludge and waste activated sludge. |
| MLSS（Mixed Liquor Suspended Solids） | An indicator of the concentration of activated sludge in the aeration basin. Concentrations are often around 1,000 to 2,000 mg/L with the conventional activated sludge process and 2,000 to 5,000 mg/L with the OD method. [Abbreviations] MLSS(Mixed Liquor Suspended Solids) |
Words That Start With O
| Overhaul | The process of disassembling a mechanical product down to its parts, cleaning, and reassembling them to restore its original performance state (in short, disassembly, inspection, repair, and adjustment). [Abbreviations] OH |
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| Oxidation ditch method | An activated sludge process in which an aerator is installed in the circulating waterway. There are two types of OD methods: one in which treated water is directly extracted from part of the waterway and the other in which a sedimentation tank is installed. The latest mainstream method is to create aerobic and anaerobic zones by carefully arranging the aerator to prevent pH decrease and remove nitrogen. [Abbreviations] OD method |
PQR
Words That Start With P
| Phosphorus removal | Phosphorus compounds (mainly inorganic or organic phosphates) in various states within wastewater must be removed to prevent eutrophication of water areas. Removal methods are roughly divided into two methods: biological and physicochemical methods. The physical method includes the coagulation sedimentation method, in which phosphorus is precipitated out as an insoluble salt by adding coagulants such as aluminum salt, iron salt, or calcium salt. Biological methods include the simultaneous coagulation sedimentation method, in which phosphorus is aerobically incorporated by microorganisms in high concentration as nutrient salt and then removed outside the system or released by an anaerobic tank and removed in a final sedimentation basin by adding a coagulant. |
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| Polyaluminum chloride | Polyaluminum chloride. Used as an inorganic coagulant. [Abbreviations] PAC |
| Primary clarifier / primary sedimentation tank | A facility to allow solids with high specific gravity, mainly organic matter, in sewage to settle out (called primary treatment). |
| Public sewer | A sewerage system managed by a local municipality to remove or treat sewage mainly in urban areas, which has a terminal treatment plant or is connected to a river basin sewerage system, and has a structure in which culverts make up a sizable proportion of its drainage facilities for sewage drainage. |
Words That Start With R
| Raw sludge | Sludge settled in the primary sedimentation basin. No processing is done at all. This is the sedimentation of raw water from which most of the impurities were removed before treatment. |
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STU
Words That Start With S
| Safety Data Sheet | It describes information necessary for the safe handling of chemical products (name, name of manufacturing company, properties of chemical substances, handling methods, types of hazards and toxicity, safety measures, emergency measures, etc.). It is an instruction manual distributed for each product by suppliers of chemical products to handling businesses to prevent accidents related to chemical products. [Abbreviations] SDS(Safety Data Sheet) |
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| Sand filtration | Filters and a suspended solid removal device having a sand layer. In the case of multilayer filtration, coarse grains or low-density grains should be dominant in the upper part of the fluid to be filtered. |
| Screen | Scraping equipment used at treatment plants to remove debris and dirt from the water before treatment. |
| Scum | Solids floating on the surface of the water in anaerobic filter bed tanks, sedimentation tanks, etc. If there is too much scum, it is likely that the process is not properly running. [Related term] Pressure flotation treatment |
| Secondary effluent | It is treated water, the supernatant from the final sedimentation basin, that has been disinfected by sand filtration . It can be used to flush toilets and water plants. |
| Septic tank | A system that purifies and treats toilet sewage (human waste) and domestic wastewater from kitchens, baths, laundry, etc., by taking advantage of microorganisms. Treated water is discharged outside of the final treatment sewerage system. It does not include “human waste treatment facilities” set up by municipalities. Specifically, they range from household septic tanks used in stand-alone houses to communal wastewater treatment facilities (community sewage treatment facilities) used in apartment complexes, residential complexes, and communities. There are two types of septic tanks: “flush toilet wastewater purifiers” which treat only human waste (domestic wastewater is discharged untreated) and “combined treatment type septic tanks” which treat both human and domestic wastewaters. Since the Onsite Wastewater Treatment Equipment Septic Law (1983) has been amended to prohibit the construction of new flush toilet wastewater purifiers, the term “septic tank” has come to mean a combined treatment type septic tank. These tanks have the same level of purification capacity as a sewerage system, removing 90% of the pollutants within raw wastewater. The installation of these tanks is subsidized by the national and local governments to reduce the financial burden on individuals. |
| Sludge | Generally, it refers to suspended solids present in water, which have precipitated or surfaced and become muddy, such as sludged pollutants that are separated from water in sedimentation tanks at water treatment facilities for industrial wastewater, sewage, and purified water, and sediment deposited on the bottom of rivers, lakes, and marshes. Sludge, a mixture of these fine solids and water, is the most common industrial waste. |
| Suspended solids | Substances suspended in water. There are two treatment methods: the filter paper method (filtration of sewage through glass fiber filter paper with a diameter of 1 µm and dry weight of particles remaining on the filter paper (unit: mg/φ)) and the centrifugal separation method. These methods are used depending on the object. Suspended solids present in wastewater are an important indicator of pollution. In water treatment, they are related to the amount of sludge generated. In dewatering machines, the chemical dosage, disposal amount, solids capture rate, etc. are calculated from the target sludge and filtrate SS values. [Abbreviations] SS(Suspended Solids) |
Words That Start With T
| Total dissolved solid (and moisture content) | TS is the residual material when the sample is evaporated to dryness and then dried at 105 to 110°C for 2 hours (a long time is required depending on the sample amount). The water content is calculated from the amount of water evaporated. TS is used to estimate the total amount of components present in wastewater. The salt content can be roughly predicted from the difference with SS. For the dewatering machine, the solid disposal amount is calculated from the TS and sludge cake water content. [Abbreviations] TS(Total Solids) |
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VWX
Words That Start With V
| VTS（Volatile Total Solids） | The amount of a substance that volatilizes when TS is heated to a high temperature of 601°C is a guide of the amount of organic matter. It is one of the factors that affect dewatering performance; the higher the VTS, the harder it tends to be for the moisture content of the dewatered cake to decrease. If the VTS is too high, it is difficult to reduce the water volume. |
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Words That Start With W
| Waste activated sludge/excess sludge/surplus activated sludge | When sewage is treated in an aeration tank, microorganisms feed on organic matter and purify the water, but the microorganisms themselves multiply. As a result of proliferation, excess sludge is removed and then disposed of. The unwanted sludge is referred to as waste activated sludge. |
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| Water content | The water content in a material (unit: %). In sludge, etc., anything other than water of the moisture content is called TS. (See TS.) |