GLOSSARY

Base flow: sustained flow of a stream in the absence of direct runoff. It includes natural and human-induced streamflows (USGS).

Basin: an area of land that drains all the streams and rainfall to a common outlet such as the outflow of a reservoir, mouth of a bay, or any point along a stream channel (USGS).

Biodegradation: is the process by which organic substances are decomposed by micro-organisms (mainly aerobic bacteria) into simpler substances such as carbon dioxide, water and ammonia. (OECD)

Biofouling: This refers to the adhesion and growth of microorganisms on the membrane surface. It results in a loss of membrane performance. Membrane processes other than MF and UF commonly used in MBRs and posttreatment after conventional activated sludge process, NF, and RO may have more biofouling (Jiang, 2007).

Biological Activity Reaction Test (B.A.R.T.): A test typically used to monitor the population size/activity of specific groups of bacteria. Particularly iron-related, sulfate-reducing and heterotrophic aerobic bacteria (Source: AWC).

Biosolids: A primarily organic solid product produced by wastewater treatment processes that can be beneficially recycled. The word biosolids is replacing the word sludge when referring to treated waste. (Sacramento State)

Bipolar electrodialysis (EDBM): It is a membrane technique that uses the particular property of the bipolar membrane which consists in dissociating water (H+ and OH-) under the action of an electric field (water splitting). A bipolar electrodialysis module (stack) consists of the assembly of bipolar and monopolar membranes (cationic/anionic) that allow the conversion of saline solutions (mineral or organic) into acids and bases. This term is provided by Flor Etchebarne - Water Treatment Business Manager at Eurodia Group.

BOO: (build, own, operate). Contracting model. This type of agreement requires the private provider to build and operate the assets for the provision of the service. In this particular case, the State will only regulate and supervise the provision of the public service, since the ownership of the asset always belongs to the provider investor.

BOOT: (build, own, operate and transfer). Contracting model. In the Public-Private Partnerships established under the BOOT contractual figure, the assets are built and operated by the private company. In this sense, the ownership of these assets belongs to the private consortium until the end of the contract term, at which time they must be transferred to the State. However, the private provider has the right to charge for the direct use of the assets. 

Boron: A chemical element of atomic number 5, atomic mass 10.81 and symbol B ; it is a solid, brittle nonmetal and, in its crystalline form, almost as hard as diamond, found in nature only in combination with other elements; it is used in the metallurgical industry and in nuclear reactors (Source: Oxford Languages). In agriculture, boron is essential for plant growth in relatively small amounts. Reverse osmosis membrane rejection for boron in seawater is typically lower than other ions, around 90% (LG CHEM).

BOT: (build, operate and transfer). Contracting model. This type of contract establishes that the project vehicle company (SVP) must build, operate and then transfer the assets or all the components of the project to the State. In other words, the private company is in charge of executing the work at its own risk and, at the end, charges for the direct use of the project.

Brackish Water: according to the definition of the adjective brackish given by the RAE, it is water with salt. However, in the field of water treatment, it is usually applied to saltwater that does not come from the sea.

Brine mining: Brine mining consists of obtaining salt and chemical products from this salt concentrate. Some other salts or chemical products that can be obtained from the concentrate arise greater interest for their economic value, whether it comes from seawater desalination or brackish water. On the one hand, we can generate Sodium hypochlorite in situ through technologies like electrochlorination or use new technologies based on different variants of electrodialysis to produce chemical products, like Hydrochloric acid or Sodium hydroxide. (Sacyr)

Brownfield projects: A brownfield project is one that carries constraints related to the current state of the site. In other words, the site might be contaminated or have existing structures that have to be teared down or modified in some way before the project can move forward. (HMC Architects)

Buffer tank: The aim of a buffer is to realize a consistent volume and possibly a consistent quality. It is implemented to allow further purification processes to run as effectively as possible. The buffer can be in-line or off-line. In-line buffering involves the entire quantity of wastewater flowing through the buffer tank. In off-line buffering, only part of the wastewater flows into the buffer tank at specific moments (e.g. to cope with accidents or very high volumes). (Source: Emis).

BWRO: Reverse Osmosis Water Desalination

Capital expenditures (CapEx): are major purchases a company makes that are designed to be used over the long term. (Source: Investopedia)

Carbon footprint: The set of greenhouse gasses emissions (CO2, CH4, Nitrous oxide N2O, hydrofluorocarbons HFCs, Perfluorocarbons PFCs and sulphur exafluoride SF) of the Life Cycle, attributable to an organization or a product are called Carbon Footprint (CF). (Source: https://www.ccpb.it/en/blog/certificazione/carbon-and-water-footprint/)

Chemical attack of the membrane: The chemical degradation of the membrane through either end group or functionality attack lowers the molecular weight of the polymer, which reduces mechanical properties (Source: Cortney Mittelsteadt, ... Jason Willey, in Electrochemical Energy Storage for Renewable Sources and Grid Balancing, 2015).

Chlorination: Chlorination of wastewater is a method of chlorine disinfection used in wastewater and drinking water treatment.  It is used to prevent the transmission of diseases and to prevent the development of microscopic algae that cloud the water. Chlorine is added to the wastewater in sufficient quantity to react with all reducing substances, organic matter and ammonia, forming organic chlorine and chloramine compounds (iAgua).

Chlorination systems: traditional system for water disinfection. To be effective, this system also requires proper water maintenance: good filtration, cleaning of surfaces and good water condition (no turbidity and proper pH).

Circular economy: In the water context, it is defined as an economic concept that is interrelated with sustainability. The objective is that the value of products, materials and resources (water, energy, others) is maintained in the economy for as long as possible, and that waste generation is minimized.

Cleaning in place (CIP):   Cleaning in Place (CIP) refers to the use of a mix of chemicals, heat and water used to clean machinery, vessels or pipe work without dismantling the plant (Source: Burkert).

Closed Circuit Reverse Osmosis (CCRO): combines the benefits of dead-end filtration with the strengths of crossflow filtration. Using standard components configured in a single-stage design, recovery, flux and crossflow are uncoupled with standard triggers to purge concentrate based on volumetric recovery, pressure and/or conductivity. This flexibility provides a level of efficiency and reliability that can only be achieved with the CCRO process. (Source: Kansas Water Technologies)

Coarse screening: Coarse screens remove large solids, rags, and debris from wastewater, and typically have openings of 6 mm (0.25 in) or larger. Types of coarse screens include mechanically and manually cleaned bar screens, including trash racks. (Source: EPA)

Condensation: the process of water vapor in the air turning into liquid water. Water drops on the outside of a cold glass of water are condensed water. Condensation is the opposite process of evaporation (USGS).

Contact angle analysis: test where the contact angle is measured to obtain information on how hydrophilic or hydrophobic a surface is (Source: AWC).

- Conventional electrodialysis (EDC): Allows purification, concentration and demineralization. Two types of membranes are used: Cationic membranes that only allow the passage of cations and anionic membranes that only allow the passage of anions. They are impermeable to liquids. An electrodialysis module (stack) is composed of a large number of pairs of cells that delimit the product and brine compartments. This term is provided by Flor Etchebarne - Water Treatment Business Manager at Eurodia Group.

Conveyance loss: water that is lost in transit from a pipe, canal, or ditch by leakage or evaporation. Generally, the water is not available for further use; however, leakage from an irrigation ditch, for example, may percolate to a groundwater source and be available for further use. (USGS).

Dam: A dam is a barrier that stops or restricts the flow of surface water or groundwater. The reservoirs created by dams not only prevent flooding, but also provide water for activities such as irrigation, human consumption, industrial use, aquaculture and navigability.

DB: (Design-Build) Contracting Model. Construction contract where the design and construction of a structure are the responsibility of the same contractor.

DBFO: (Design-Build-Finance-Operate) Contracting model. The private sector party obtains a contract to design, build, finance and operate a capital project. In consideration for fulfilling its obligations under the agreement, the private sector party may be paid by the government agency (e.g., availability payments) or from fees charged to the end users of the project. The government or government-owned entity holds ownership of the project.

Desalination: activity to remove all or most of the salt from seawater in order to make it potable or, in any case, suitable for productive or recreational use.

Differential pressure: is the difference in pressure between two points in a system.  For filtration applications, the upstream side [A] is positioned before the filter [B], whereas the downstream side [C] is after the filter. A differential pressure sensor can be used to monitor the cleanliness of a filter in either liquid or gas applications. (Source: TE Connectivity)

Direct Potable Reuse (DPR): Refers to the treatment of wastewater and its reuse as potable water. Direct means that the water does not pass through an environmental buffer prior to standard treatment (Source: Toray).

Discharge: the volume of water that passes a given location within a given period of time. Usually expressed in cubic feet per second (USGS).

Disinfection: the process designed to kill or inactivate most microorganisms in water or wastewater, including essentially all pathogenic (disease-causing) bacteria. There are several ways to disinfect, with chlorination being the most frequently used in water and wastewater treatment plants. (Sacramento State)

Domestic water use: water used for household purposes, such as drinking, food preparation, bathing, washing clothes, dishes, and dogs, flushing toilets, and watering lawns and gardens (USGS).

Drought: a period of drier-than-normal conditions that results in water-related problems (USGS).

Electrodeionization (EDI)  It is a combination of electrodialysis and ion exchange. Its function is to remove ions from water. The technology consists of a combination of ion exchange resins, both cationic and anionic, ion-selective membranes, an anode, a cathode and the cyclic application of an electric potential. In combination with reverse osmosis (RO), EDI as a final stage allows obtaining deionized water with a much lower salt concentration than that produced by RO.

Electrodialysis (ED): An electrochemical separation process where ions are transferred through ion exchange membranes by means of a direct current (DC) voltage. The process uses a driving force to transfer ionic species from the source water through the cathode (positively charged ions) and anode (negatively charged ions) to a concentrated wastewater stream, creating a more dilute stream (called product). This term is provided by Flor Etchebarne - Water Treatment Business Manager at Eurodia Group.

Electrodialysis reversal (EDR): This is a variation of the EDC process, which uses electrode polarity reversal. EDR works in the same way as EDC, except that the DC polarity is reversed two to four times per hour. In this way, the dilute and concentrated source water compartments are also reversed, as are the chemical reactions at the electrodes. This reversal acts as a self-cleaning mechanism that minimizes fouling and extends membrane life. The configuration is very similar to that of an EDC system, except for the presence of reversing valves This term is provided by Flor Etchebarne - Water Treatment Business Manager at Eurodia Group.

Effluent: the output or outflows from any system that discharges water flows as a result of urban, industrial, or agricultural activities.  

Emerging Contaminants: Contaminants that are discovered in the water supply, chemicals that had not previously been detected (or were previously found in much lower concentrations). These chemicals are known as "contaminants of emerging concern" or simply "emerging contaminants".

Energy Dispersive X-ray Spectroscopy (EDS): standard procedure to identify the elemental composition of a sample. It provides relative stoichiometric ratios of elements so that an empirical formula can be determined (Source: AWC).

Energy recovery turbines: Transformation of pressure energy into mechanical energy and with the possibility of later conversion to electrical energy by means of an alternator (Source: Befesa Agua, S.A.U.).

Energy recuperator: Mechanical equipment designed to reuse energy from brine water.  They can be isobaric or centrifugal equipment.

Environmental, social, and governance (ESG):  an increasingly important part of the investment process. For investment professionals, a key motivation in the practice of considering environmental, social, and governance (ESG) issues as part of their financial analysis is to gain a fuller understanding of the companies in which they invest. (Source: CFA Institute)

Equalization tanks (EQ): retain high fluctuating flows; they are designed to control influent flow so that secondary and tertiary processes receive a consistent flow (Source: Aeration Industries International).

EPC: (Engineering - Procurement - Construction) Under this model, the financing to carry out preliminary studies, publish prequalification and tender documents, covering all technical, legal and guarantee disciplines, as well as the investment or operation of the plants are covered by these administrations or utilities.

 EPCC: (Engineering, Procurement, Construction and Commissioning)

Erosion: Weathering and modeling of the earth's crust caused by the action of wind, rain, fluvial, maritime and glacial processes, and by the action of living beings.

Estimated flow: A rough guess of the amount of flow in a collection system. When greater accuracy is needed, flow could be computed using average or typical flow quantities. Even greater accuracy would result from metering or otherwise measuring the actual flow. (Sacramento State)

Evaporation: the process of liquid water becoming water vapor, including vaporization from water surfaces, land surfaces, and snow fields, but not from leaf surfaces (USGS).

Evapotranspiration: the sum of evaporation and transpiration (USGS).

Feedwater: water that undergoes purification or preheating and is then supplied to boilers for hot water and steam production, or it can remain still. It is typically found in thermal power plants where it is stored and conditioned in tanks, known as boiler feedwater. Feedwater is also used in other industrial facilities, such as in the petrochemical industry, where boilers are an integral element of production. Quality water is required to mitigate scaling, rust formation and other corrosive effects (Source: Corrosionpedia)

Fine screening: a pre-treatment process allowing finer separation than coarse screens of the solid waste contained in the raw water. (Source: Equip Water)

Flocculation: The gathering together of fine particles after coagulation to form larger particles by a process of gentle mixing. This clumping together makes it easier to separate the solids from the water by settling, skimming, draining, or filtering. (Sacramento State)

Flujo de retorno de tratamiento de aguas residuales: agua devuelta al medio ambiente por las instalaciones de tratamiento de aguas residuales (USGS).

Forever chemicals: PFAS (Per- and Polyfluoroalkyl Substances) are a group of synthetic chemicals used to prevent corrosion, reduce friction and make products waterproof and stain resistant (The Guardian).

Freshwater, fresh water: water that contains less than 1,000 milligrams per liter (mg/L) of dissolved solids; generally, more than 500 mg/L of dissolved solids is undesirable for drinking and many industrial uses (USGS).

Fujiwara test: It is performed to determine if the membrane has been exposed to halogens. It detects the presence of organically bound halogen compounds. Halogens such as chlorine or bromine bind to the membrane surface and alter its chemistry, resulting in reduced salt rejection (Source: AWC).

Giardiasis: a disease that results from an infection by the protozoan parasite Giardia Intestinalis, caused by drinking water that is either not filtered or not chlorinated. The disorder is more prevalent in children than in adults and is characterized by abdominal discomfort, nausea, and alternating constipation and diarrhea (USGS).

Gravity flow: Water or wastewater flowing from a higher elevation to a lower elevation due to the force of gravity. The water does not flow due to energy provided by a pump. Wherever possible, wastewater collection systems are designed to use the force of gravity to carry waste liquids and solids. (Sacramento State)

Greenfield projects: Those that lack constraints imposed by prior work on the site. Typically, what a greenfield project entails is development on a completely vacant site. (HMC Architects)

Greywater: wastewater from clothes washing machines, showers, bathtubs, hand washing, lavatories and sinks (USGS).

Green energy: is any energy type that is generated from natural resources, such as sunlight, wind or water. It often comes from renewable energy sources that don’t harm the environment through factors such as releasing greenhouse gases into the atmosphere. (Fuente: https://www.twi-global.com/)

Greenwashing: The process of conveying a false impression or providing misleading information about how a company's products are more environmentally friendly (Investopedia).

GRIP Project: Groundwater Reliability Improvement Program. Project for the treatment of wastewater to potable quality to replenish water in groundwater basins (Source: Toray).

Groundwater Recharge (GWR): Planned use of recycled water to replenish a groundwater basin or aquifer that has been designated as a source of water for a public water system (Source: Toray).

Hardness: a water quality indication of the concentration of alkaline salts in water, mainly calcium and magnesium. If the water you use is "hard" then more soap, detergent or shampoo is necessary to raise a lather (USGS).

High-temperature electrodialysis: This is a variant of conventional and bipolar electrodialysis that allows solutions to be treated at high temperatures (up to 65°C). This temperature level allows, depending on the application, to reduce the viscosity of the treated solutions, to reduce energy consumption and to reduce the development of most of the microorganisms that can disturb the functioning of the modules (stacks) (Eurodia).

Hectoliter (hl): a unit of measurement equal to 100 liters.

Humic/Fulvic Acid Analysis: A test in which the membrane is soaked in a high pH solution to remove deposits of natural organic matter. That solution is then filtered to remove suspended solids and the pH is lowered to ~ 1. Humic acids become completely insoluble at that pH. Finally, the solution is filtered through a 0.1 µm filter (Source: AWC).

Hydroelectric power water use: the use of water in the generation of electricity at plants where the turbine generators are driven by falling water (USGS).

Hydrologic cycle: the cyclic transfer of water vapor from the Earth's surface via evapotranspiration into the atmosphere, from the atmosphere via precipitation back to earth, and through runoff into streams, rivers, and lakes, and ultimately into the oceans (USGS).

Hydrograph: The hydrograph is a graph that shows the variation over time of some hydrological information such as: water level, flow, sediment load, among others.

Improved source of water: Improved drinking-water sources are defined as those that are likely to be protected from outside contamination, and from faecal matter in particular. Improved water sources include household connections, public standpipes, boreholes, protected dug wells, protected springs and rainwater collection. Unimproved water sources include unprotected wells, unprotected springs, surface water (e.g. river, dam or lake), vendor-provided water, bottled water (unless water for other uses is available from an improved source) and tanker truck-provided water. (World Health Organization)

Industrial water use: water used for industrial purposes in such industries as steel, chemical, paper, petroleum refining and other (USGS).

Infiltration: flow of water from the land surface into the subsurface (USGS).

Injection well: refers to a well constructed for the purpose of injecting treated wastewater directly into the ground. Wastewater is generally forced (pumped) into the well for dispersal or storage into a designated aquifer. Injection wells are generally drilled into aquifers that don't deliver drinking water, unused aquifers, or below freshwater levels (USGS).

Installed capacity: The maximum amount of water that a water treatment or desalination plant can treat in a given period of time and under specific conditions designated by the manufacturer. The installed capacity is usually calculated in cubic meters.

Internal membrane scaling: the deposition of particles on the inside of a membrane. Scaling results in higher energy use and shorter membrane life.

Ion Concentration (TDS): To maintain water production when the feed water concentration is increased, we need to increase the pressure as the osmotic pressure to overcome increases. If on the other hand, with higher concentration we maintain the pressure, the permeate flow will decrease and therefore the conversion. The permeate water quality worsens in any case (Source: Befesa Agua, S.A.U.).

Ion Exchange: is a water treatment process generally used for water softening or demineralization, although it is also used to remove other substances from water in processes such as desalination, deionization, and disinfection.

Ion exchange resins: Ion-exchange resins are cross-linked high molecular weight compounds which contain acidic or basic groups which are the active centres of these resins. Ion-exchange resins find very wide application for the softening of water' the purification of sea water, the extraction of metals from sewer water and rivers, the separation of electrolytes, rare-earth elements, isotopes and amino acids, in the manufacture of foods, in analytical chemistry, etc. (Ye.L. GEFTER)

Irrigation water use: water application on lands to assist in the growing of crops and pastures or to maintain vegetative growth in recreational lands, such as parks and golf courses (USGS).

Key Performance Indicators (KPIs): Are widely recognized as a basis for evaluating water utility operations in developing countries and for designing both regulatory and managerial incentives that improve performance.

Legacy pollutants: contaminants that have been left in the environment by sources that are no longer discharging them such as an old industry that has since left the area. (University of Southern Maine)

Liquid Industrial Waste (LIW). These are "waters" resulting from the processing and manufacturing of different products that must be properly treated to avoid harming the sewage system, and finally lakes, rivers and the sea. Term mainly used in Chile.

Livestock water use: water used for livestock watering, feed lots, dairy operations, fish farming, and other on-farm needs (USGS).

Loss-on-ignition analysis: A test in which the material is first dehydrated at 105°C overnight. It is then heated at 450°C for 8 hours to volatilize the organic compounds. The amount of weight loss can be directly correlated to the organic content (Source: AWC).

Mechanical Stress: is a measure of internal resistance exhibited by a body or material when an external force is applied to it. In RO membranes it can happen through abrasion.

Membrane Autopsy: Used to identify the cause of decreased performance of a membrane system and to evaluate the condition of the membranes in the system to determine if a replacement would be justified (AWC).

Membrane Biological Reactor (MBR): this is the name given to ultrafiltration applied as part of secondary effluent treatment. It consists of UF membranes with similar characteristics to those used for water treatment. It is used as a replacement for the clarification stage in a conventional activated sludge effluent treatment plant (Source: Fluence).

Membrane chemical products: specialty chemicals for membrane-based water treatment systems. These include membrane pretreatment chemicals, membrane cleaners, coagulants, flocculants, membrane preservatives

Membrane chemical solubility analysis: A test that exposes contaminants on a membrane through acidic and caustic solutions. Organic contaminants are dispersed in caustic solutions and iron and manganese contaminants turn acidic solutions yellow (Source: AWC).

Membrane damage: when chemicals react with the membrane and cause damage to it (Source: PCA Water Treatment).

Membrane deformation: is a common phenomenon in pressurized membrane processes. It alters the transport and structural characteristics of membranes and hence can lead to a lower than estimated process performance (Source: Peters, C., Yee, D., Hankins, N., She, Q., 2021).

Membrane Dye Test: A test in which a test pressure dye solution is applied to the feed side of the membrane. It has a high molecular weight that the RO should readily reject. Any dye passage would indicate membrane damage, usually mechanical, though sometimes chemical. The degree of dye passage and the pattern provide clues as to how the damage may have occurred (Source: AWC).

Membrane flow configurations: Membrane systems can be operated in various process configurations. There are two main flow configurations of membrane processes: dead-end and crossflow filtrations.

Membrane flux: related to the amount of water that reverse osmosis, nanofiltration, or ultrafiltration membrane produces per active area of the membrane.

Membrane performance test: A test performed according to the manufacturer's quality control test specifications. A test solution is prepared using a specified salt concentration, and at a given feed pressure and feed flow rate (Source: AWC).

Membrane recovery: it is the recovery of reverse osmosis membranes at the end of their useful life, which reduces the impact associated with treatment plant waste and its implementation costs. 

Membrane weight measurement: The weight measurement provides information on the severity of scaling and possible structural damage to the membrane. Scaled membranes are heavier than clean membranes (Source: AWC).

Microfiltration: membrane filtration process in which hydrostatic pressure pushes a liquid towards a semi-permeable membrane. Microfiltration membranes have a pore size of 0.1-10 µm.

Milligrams per liter (mg/l): a unit of the concentration of a constituent in water or wastewater. It represents 0.001 gram of a constituent in 1 liter of water. It is approximately equal to one part per million (PPM) (USGS).

Minimum liquid discharge (MLD): near-zero liquid discharge processes that produce highly concentrated waste streams. Typically, MLD is defined as a process that recovers at least 95% of the water (Cleanteq Water).

Mining water use: water use during quarrying rocks and extracting minerals from the land (USGS).

Moving bed biofilm reactor (MBBR): is considered an Advanced Wastewater Treatment (AWT), which combines the best of Conventional Activated Sludge (CAS) and biofilter processes, making use of suspended biomass and attached biomass. (Source: Andreia D. Santos, Rui C. Martins, Rosa M. Quinta-Ferreira, Luis M. Castro)

Multi-layer filter: Process in which the water passes through various layers of filter material with increasing fineness in the direction of filtration. Dirt is agglomerated in the various layers of the filter depending on its size. Multi-layer filters can take up large quantities of solids. (Source: HydroGroup)

Multimedia filters: They are designed to filter suspended solids in water through several layers of filter media from coarser to finer.  This design results in larger particles being trapped in the upper layers and smaller particles in the lower layers.

Nature-based solutions (NBS): a new concept that encompasses all actions that rely on ecosystems and the services they provide to respond to various societal challenges such as climate change, food security or disaster risk (IUCN).

Natural Organic Matter (NOM): Organic material that is formed from plants and animals present in natural waters (in their natural or untreated state), such as lakes, rivers and reservoirs (Source: Green Facts).

Nanofiltration: is a membrane filtration process in which hydrostatic pressure pushes a liquid against a semi-permeable membrane. The nanofiltration process can retain particles with a size of 0.1 nm-0.001.

Nano-structured Membranes: nanostructured membranes can be defined as membranes having internal or surface nanostructure. The nanostructured membrane can be a dense membrane incorporated with nanomaterials, a porous membrane with nanoscale pores, or a combination of both. (Witopo Salim, and W.S. Winston Ho (2019) Recent developments on nanostructured polymer-based membranes)

Nephelometric turbidity unit (NTU): unit of measure for the turbidity of water. Essentially, a measure of the cloudiness of water as measured by a nephelometer. Turbidity is based on the amount of light that is reflected off particles in the water (USGS).

Non-point source (NPS) pollution: pollution discharged over a wide land area, not from one specific location. These are forms of diffuse pollution caused by sediment, nutrients, organic and toxic substances originating from land-use activities, which are carried to lakes and streams by surface runoff. Non-point source pollution is contamination that occurs when rainwater, snowmelt, or irrigation washes off plowed fields, city streets, or suburban backyards. As this runoff moves across the land surface, it picks up soil particles and pollutants, such as nutrients and pesticides (USGS).

Non-revenue water (NRW): the difference between the volume of water entering the network and the water charged to the end user. NRW is expressed as a percentage.

Operating expenses (OpEx): day-to-day expenses a company incurs to keep its business operational. (Source: Investopedia)

Outfall: the place where a sewer, drain, or stream discharges; the outlet or structure through which reclaimed water or treated effluent is finally discharged to a receiving water body (USGS).

Oxidation ditch: a modified activated sludge biological treatment process that utilizes long solids retention times (SRTs) to remove biodegradable organics. Oxidation ditches are typically complete mix systems, but they can be modified to approach plug flow conditions. (Source: EPA)

Oxidation ponds: also called lagoons or stabilization ponds, are large, shallow ponds designed to treat wastewater through the interaction of sunlight, bacteria, and algae. Algae grow using energy from the sun and carbon dioxide and inorganic compounds released by bacteria in water. (Source: Britannica).

Osmosis: is a physical phenomenon related to the movement of a solvent through a semi-permeable membrane. Such action implies a simple diffusion across the membrane without energy consumption. Water osmosis is an important biological phenomenon for the cellular metabolism of living beings.

Osmotized water: water produced from the Reverse Osmosis process which is of very high purity.

Ozonation: Ozonated water is a water potabilization method that consists of diluting ozone in water. Ozone is a disinfectant of bacteria, viruses, parasites and helps in the micro-flocculation and reduction of suspended solids (iAgua).

Particle size: the diameter, in millimeters, of suspended sediment or bed material (USGS).

Particle-size classifications are:
[1] Clay—0.00024-0.004 millimeters (mm);
[2] Silt—0.004-0.062 mm;
[3] Sand—0.062-2.0 mm; and
[4] Gravel—2.0-64.0 mm.

Parts per million: the number of "parts" by weight of a substance per million parts of water. This unit is commonly used to represent pollutant concentrations (USGS).

Pathogen: a disease-producing agent; usually applied to a living organism. Generally, any viruses, bacteria, or fungi that cause disease (USGS).

PFAS: Perfluoroalkylated and polyfluorinated substances are widely used, long-lasting chemicals whose components break down very slowly over time. Many PFASs are found in the blood of people and animals around the world and are present at low levels in a variety of food products and in the environment. PFASs are found in water, air, fish and soil in locations across the country and around the world. Scientific studies have shown that exposure to some PFASs in the environment may be associated with adverse health effects in people and animals. There are thousands of PFAS chemicals, and they are found in many consumer, commercial and industrial products. (Environmental Protection Agency)

PFAS sensor:  sensors that have been developed for PFAS detection by a molecular detection mechanism. There is a big need for fast, inexpensive, robust, and portable methods to detect PFAS in the field. This would allow environmental laboratories and other agencies to perform more frequent testing to comply with regulations. In addition, the general public would benefit from a fast method to evaluate the drinking water in their homes for PFAS contamination. (Menger, R. et al, 2021)

pH: a measure of the relative acidity or alkalinity of water. Water with a pH of 7 is neutral; lower pH levels indicate increasing acidity, while pH levels higher than 7 indicate increasingly basic solutions (USGS).

PPP: Public-Private Partnership (PPP) is a type of contract that can be self-sustaining or co-financed. In this type of association between the State and the private sector, the latter provides public services or executes and runs specific public infrastructure works within a given time frame.

Permeate: related to a liquid: to diffuse through or penetrate something.

Permeate flow:  is a function of the Net Driving Pressure (NDP), temperature and membrane condition (Source: RO Chemicals).

Point-source pollution: water pollution coming from a single point, such as a sewage-outflow pipe (USGS).

Polychlorinated biphenyls (PCBs): a group of synthetic, toxic industrial chemical compounds once used in making paint and electrical transformers, which are chemically inert and not biodegradable. PCBs were frequently found in industrial wastes, and subsequently found their way into surface and groundwaters. As a result of their persistence, they tend to accumulate in the environment. In terms of streams and rivers, PCBs are drawn to sediment, to which they attach and can remain virtually indefinitely (USGS).

Potable water: water of a quality suitable for drinking (USGS).

PPP: Public Private Partnership (PPP) is a type of concession, which can be self-sustaining or co-financed. In this partnership scheme between the State and the private sector, the latter provides public services or executes and exploits certain public infrastructure works, in a determined period of time.

Pressure Exchange Systems (PES): Transfer of energy from a high-pressure fluid (brine) to a low-pressure fluid (water entering the membranes) by taking advantage of the incompressible properties of water (Source: Befesa Agua, S.A.U.).

Primary clarification: A process to reduce the content of suspended solids and contaminants embedded in those suspended solids.

Primary wastewater treatment: the first stage of the wastewater-treatment process where mechanical methods, such as filters and scrapers, are used to remove pollutants. Solid material in sewage also settles out in this process (USGS).

Prismatic Elemental Mapping (PEM): a test that uses a scanning electron microscope (SEM) and an energy dispersive X-ray spectrometry (EDS) detector to identify individual chemical elements embedded in membranes (Source: AWC).

Process Water: water used for multiple purposes, such as cooling systems, boilers, processes, steam production, etc. 

Produced Water: is a term used in the oil industry to describe water produced along with oil and gas.

Public water use: water supplied from a public-water supply and used for such purposes as firefighting, street washing, and municipal parks and swimming pools (USGS).

Pulse Flow RO (PFRO): technology for operating Reverse Osmosis water reuse systems that enables high recovery, high flux and Chloramine-free operation. PFRO constantly changes the osmotic and hydraulic conditions, thus greatly diminishing biofouling and scaling. (Source: 2020, B. Liberman, L. Eshed, G. Greenberg)

Raw water: Raw water is water that has not received any treatment and has not yet been introduced into the distribution network. It is found in natural sources and reservoirs, both surface water and groundwater.

Reclaimed wastewater: wastewater-treatment plant effluent that has been diverted for beneficial uses such as irrigation, industry, or thermoelectric cooling instead of being released to a natural waterway or aquifer (USGS).

Recycled Water: is the reuse of treated wastewater for beneficial purposes, such as agricultural and landscape irrigation, industrial processes, toilet flushing, and replenishment of a groundwater basin.

Retentate: Retentate or RO brine is a concentrated impaired water source resulting from reverse osmosis water filtration. The other output of RO is purified water (the permeate). (ForwardOsmosis Tech)

Reverse Osmosis: For the Royal Academy of Engineering, this is the process that separates one component from another in a solution through the force applied to a semi-permeable membrane.

RO Membranes: Semi-permeable membranes used in the Reverse Osmosis process to remove ions, molecules and larger particles in drinking water.

Saline water: water that contains significant amounts of dissolved solids (USGS).

Salt Passage: ratio between the salt concentrations of the product and the feed, measured as a percentage or percentage per one. = Cp / Ca (Source: Befesa Agua, S.A.U.).

Salt Rejection: ratio between the concentration difference between the feed and permeate and the feed concentration = (Cp- Ca) / Ca (Source: Befesa Agua, S.A.U.).

Scaling:  the deposition of particles on a membrane, causing it to plug. It is an unwanted effect that can occur during nano filtration and Reverse Osmosis processes. Scaling causes a higher energy use and a shorter life span of the membranes, because these will need cleaning more often. (Lenntech)

Scanning electron microscope (SEM): Scanning electron microscopes have a much higher resolution and magnification than an optical microscope. They scan a sample with a focused electron beam and deliver images with information about the topography and composition of the sample (Source: AWC).

Screening: the aim of grids and sieves is to remove large particles from wastewater. This can be done using a sieve (curved sieve, a drum sieve or vibrating sieve) or a grid (Source: Emis).

Seawater brine: the effluent from a desalination process that results in water with a salt concentration greater than 69 grams per liter.

Secondary clarification: allows wastewater to settle before being reintroduced into the environment or sent for further treatment, often referred to as tertiary treatment (Source: Ecolab).

Secondary wastewater treatment: treatment (following primary wastewater treatment) involving the biological process of reducing suspended, colloidal, and dissolved organic matter in effluent from primary treatment systems and which generally removes 80 to 95 percent of the Biochemical Oxygen Demand (BOD) and suspended matter. Secondary wastewater treatment may be accomplished by biological or chemical-physical methods. Activated sludge and trickling filters are two of the most common means of secondary treatment. It is accomplished by bringing together waste, bacteria, and oxygen in trickling filters or in the activated sludge process. This treatment removes floating and settleable solids and about 90 percent of the oxygen-demanding substances and suspended solids. Disinfection is the final stage of secondary treatment (USGS).

Separation: Separation Technology is the method of combining colloidal particles and extremely small solid suspensions in a wastewater stream into bigger agglomerates that may be separated using sedimentation, flocculation, filtration, centrifugation, or other processes. (Netsol Water)

Sequencing batch reactor (SBR): is a fill-and- draw activated sludge system for wastewater treatment. In this system, wastewater is added to a single “batch” reactor, treated to remove undesirable components, and then discharged. (Source: EPA).

Sleeve filters: Sleeve filters with a fineness ranging from 1 µm up to 300 µm remove all particles suspended in the water (earth, sand, rust, etc.). They are suitable for food use and drinking water. (Source: Cintropur).

Sludge Drying: a thermal drying process where thermal energy is provided to the sludge to evaporate water. The process of drying sludge reduces volume of the product, making its storage, transportation, packaging and retail easier. (Source: IWA).

Sulfates: salt formed by combining sulfuric acid and a base; obtained by reacting sulfuric acid with metals, their hydroxides and carbonates or by oxidizing a sulfide; some organic sulfates are also known, such as methyl sulfate and the sulfates of alkaloids used in medicine (Source: Oxford Languages).

Surface scaling of the membrane: the deposition of particles on the surface of a membrane. Scaling causes a higher energy use and a shorter life span of the membranes.

Surface Water Augmentation (SWA): Discharge of recycled water into a reservoir used as a source of drinking water for a public water system (Source: Toray).

Sediment: usually applied to material in suspension in water or recently deposited from suspension. In the plural the word is applied to all kinds of deposits from the waters of streams, lakes, or seas (USGS).

Sedimentation: Process by which materials transported by different agents (gravity, runoff, glaciers or wind) and coming from the erosion and weathering of rocks are deposited or precipitated, becoming sediment.

Sedimentation tanks-: wastewater tanks in which floating wastes are skimmed off and settled solids are removed for disposal (USGS).

Septic tank: a tank used to detain domestic wastes to allow the settling of solids prior to distribution to a leach field for soil absorption. Septic tanks are used when a sewer line is not available to carry them to a treatment plant. A settling tank in which settled sludge is in immediate contact with sewage flowing through the tank, and wherein solids are decomposed by anaerobic bacterial action (USGS).

Settling pond (water quality): an open lagoon into which wastewater contaminated with solid pollutants is placed and allowed to stand. The solid pollutants suspended in the water sink to the bottom of the lagoon and the liquid is allowed to overflow out of the enclosure (USGS).

Sewerage / Sewer: a system of underground pipes that collect and deliver wastewater to treatment facilities or streams (USGS).

Sewage sludge: composed of both inorganic and organic materials, large concentrations of some plant nutrients, much smaller concentrations of numerous trace elements and organic chemicals, and some pathogens. The compositions of sewage sludges vary considerably depending on the wastewater composition and the treatment processes used. (Source: Penn State University).

Sewage treatment plant: a facility designed to receive the wastewater from domestic sources and to remove materials that damage water quality and threaten public health and safety when discharged into receiving streams or bodies of water. The substances removed are classified into four basic areas:greases and fats; solids from human waste and other sources; dissolved pollutants from human waste and decomposition products; and  dangerous microorganisms. Most facilities employ a combination of mechanical removal steps and bacterial decomposition to achieve the desired results. Chlorine is often added to discharges from the plants to reduce the danger of spreading disease by the release of pathogenic bacteria (USGS).

Smart Water: This is a term related to using modern technological tools such as sensors, drones and techniques such as machine learning or big data to help optimize the water treatment process.

Supernatum: the top level of a fluid at rest; important in many applications of water and wastewater treatment. In particular, it is of concern and often measured in settling tanks and skimmers (USGS).

Suspended sediment: very fine soil particles that remain in suspension in water for a considerable period of time without contact with the bottom. Such material remains in suspension due to the upward components of turbulence and currents and/or by suspension (USGS).

Suspended solids: solids that are not in true solution and that can be removed by filtration. Such suspended solids usually contribute directly to turbidity. Defined in waste management, these are small particles of solid pollutants that resist separation by conventional methods (USGS).

SWRO: acronym for Seawater Reverse Osmosis Desalination

Temperature in RO processes: affects both osmotic pressure and water permeability across the membrane. It is generally accepted that pressure and permeate flux increase by about 0.5 bar and 3 % for each °C increase in temperature respectively. The passage of salts increases with temperature at the same rate as the flux, so as the temperature increases at constant permeate flux, the permeate quality decreases (Source: Befesa Agua, S.A.U.).

Tertiary wastewater treatment: selected biological, physical, and chemical separation processes to remove organic and inorganic substances that resist conventional treatment practices; the additional treatment of effluent beyond that of primary and secondary treatment methods to obtain a very high quality of effluent. The tertiary wastewater treatment process consists of flocculation basins, clarifiers, filters, and chlorine basins or ozone or ultraviolet radiation processes (USGS).

Thermal pollution: a reduction in water quality caused by increasing its temperature, often due to disposal of waste heat from industrial or power generation processes. Thermally polluted water can harm the environment because plants and animals can have a hard time adapting to it (USGS).

Thermoelectric power water use: water used in the process of the generation of thermoelectric power. Power plants that burn coal and oil are examples of thermoelectric-power facilities (USGS).

Trace elements: Trace elements are simply elements present in minute amounts in the environment. Trace elements include metals, such as lead and iron; metalloids, such as arsenic; and radionuclides (radioactive elements), such as radium and radon. Trace elements in streams, rivers, and groundwater have natural and humanmade sources. Rock weathering, soil erosion, and dissolution of water-soluble salts are examples of natural sources of trace elements. Many human activities also contribute trace elements to the environment—mining, urban runoff, industrial emissions, and nuclear reactions are just some of the many manmade sources. Trace elements tend to concentrate in sediment, but also can dissolve to some degree in water, and can present a risk to human and aquatic health. (USGS)

Turbidity: the amount of solid particles that are suspended in water and that cause light rays shining through the water to scatter. Thus, turbidity makes the water cloudy or even opaque in extreme cases. Turbidity is measured in nephelometric turbidity units (USGS).

Ultrafiltration: membrane filtration process, in which hydrostatic pressure pushes a liquid against a semi-permeable membrane. Ultrafiltration separates particles with a size of 0.001-0.1 µm.

Ultrapure Water. The Royal Academy of Engineering defines it as laboratory water that has been filtered and purified by reverse osmosis. The term comes from the patented commercial treatment.

UV disinfection: is the treatment of water with the use of lamps that emit ultraviolet radiation that can eliminate pathogens and produce high-quality water.

Vacuum evaporation: a technique which is characterized by transforming liquid effluent into two flows, one of high-quality water and the other comprising a concentrated waste. (Source: CondorChem Envitech)

Virtual Water: first defined by Professor J.A. Allan as water contained in products. For example, a cup of coffee requires 120 liters of water corresponding to the process of cultivation, transport, and processing of the beans.

Visual inspection of membrane: Visual inspection of a membrane is an important part of the membrane autopsy procedure. Often, fouling and mechanical damage can be observed visually (Source: AWC).

Wastewater: water that has been used in homes, industries, and businesses that is not for reuse unless it is treated (USGS).

Wastewater-treatment return flow: water returned to the environment by wastewater-treatment facilities (USGS).

Water-borne diseases: Water-borne diseases are the ones caused by pathogenic microbes spread via contaminated water. Transmission of these pathogens occurs while using infected water for drinking, food preparation, and washing clothes, among others. Many developing countries do not have proper water treatment plants, especially in the rural areas. In some places, the availability of water is so scarce that people have neither the time nor the money to afford the water purifiers or other water treatment mechanisms. (News Medical)

Water cycle: the circuit of water movement from the oceans to the atmosphere and to the Earth and return to the atmosphere through various stages or processes such as precipitation, interception, runoff, infiltration, percolation, storage, evaporation, and transportation (USGS).

Watershed: A watershed is a system, a geographical and hydrological unit, consisting of a major river and all its associated territories between the river's source and its mouth. (IUCN)

Water balance: It is based on the application of the principle of conservation of water masses. This measurement method analyzes the inflow and outflow of water from a territorial space over time. (Aquabook)

Water bodies: according to the European Environment Agency Water Glossary is any water body that has defined hydrological, physical, chemical, and biological characteristics that is useful for one or more purposes. 

Water footprint: This is the total freshwater used by a person, community, company or country to produce the goods and services consumed.

Water hammer: A water hammer is a sudden increase in pressure caused by a rapid change in pipe flow velocity that can burst pipes, rupture joints and cause damage to the pump and/or motor.

Water positive: A company is defined as Water Positive when its water mass balance is positive with respect to the difference between the generation of Purified Water and the direct or indirect consumption of Fresh Water to produce goods or services.

Water purification: The RAE states that purification is the action of making water potable (i.e., suitable for human consumption and not representing a health risk). It refers specifically to water for human consumption for drinking, and it can be done with water extracted from different sweet and brackish sources and even from effluent treatment.

Water quality: a term used to describe the chemical, physical, and biological characteristics of water, usually in respect to its suitability for a particular purpose (USGS).

Water Stress: Different international organizations define it and make it part of their goals. The European Environment Agency, through the Water Information System for Europe (WISE), states that Water Stress occurs when the water demand exceeds the amount available during a given period or when poor quality limits its use. Water stress causes the deterioration of freshwater resources in both quantity (overexploitation of aquifers, dry rivers, etc.) and quality (eutrophication, organic matter contamination, saline intrusion, etc.).

Water treatment process controller: it is an instrument with an embedded web server that through inputs and outputs of different types. It allows to supervise, control variables of different types and actuate devices to achieve a desired result (Source: Walchem).

WWF Water Risk Filter: WWF and DEG tool to assess water risks and map them. It helps prioritize actions to address water risks and improve business resilience and a sustainable future (Source: Textiles the Amazon).