Hand pumps (alias manual pumps or human-powered pumps) are a type of water-lifting device mainly serving community water supplies that can be operated manually. Human-powered pumps also include foot pumps and rope and bucket systems with or without a windlass or shadouf.

The traditional and still most common method of obtaining groundwater in rural areas of the developing world is by means of dug wells, mostly hand-dug wells. With the prior knowledge that groundwater is present and rather close to the surface, a hole (5-30 metres) is dug until the groundwater level is reached. Inflowing groundwater is collected and can be extracted with the help of pumps or buckets.

Hardware tools are technical options to optimise your water and nutrient cycle. These are physical solutions that you can see and touch with your hands such as water filters, toilets, treatment systems or technologies to recycle water and nutrients. Usually, you will nee a combination of different hardware and software tools to really make a sustainable impact.

Health is of complete physical, mental and social well-being and not merely the absence of disease or infirmity.

Health and hygiene issues in regard to water and sanitation include knowledge on the basic interrelationships between water, sanitation and health, knowledge of water-based diseases and water contaminants, as well as the management of health risks and proper hygiene behaviour.

Healthcare waste (HCW) is a by-product of healthcare that includes sharps, non-sharps, blood, body parts, chemicals, pharmaceuticals, medical devices and radioactive materials. Poor management of HCW exposes healthcare workers, waste handlers and the community to infections, toxic effects and injuries.

Heat engines, as thermal power plants are physical devices that convert thermal energy to mechanical output (which can be transformed into electricity). The mechanical output is called work, and the thermal energy input is called heat. Heat is transferred from the source, through the working body of the engine, to the sink, and in this process some of the heat is converted into mechanical energy (work) by exploiting the properties of a working substance (usually a gas or liquid).

Heavy metals are relatively dense metals (e.g. cadmium, chromates, lead, and mercury). They are usually found in commercial and industrial wastewater. Many heavy metals can have a toxic effect on living beings and in wastewater treatment, they need the to be source controlled. Most biological wastewater treatment don't remove heavy metals (although phytoremediation can be used to remove the heavy metals from the water)

A parasitic worm, i.e. one that lives in or on its host, causing damage. Some examples that infect humans are roundworms (e.g., Ascaris and hookworm) and tapeworms. The infective eggs of helminths can be found in excreta, wastewater and sludge. They are very resistant to inactivation and may remain viable in faeces and sludge for several years.

Chemical substances to get rid of competitors or pests, which influence growth and harvest of the sown plants.

HRP follow the AFP in AIWP systems. Aerobic bacteria break down dissolved organic matter and algae take up nutrients and further BOD. HRPs are designed to promote the symbiosis between the microalgae and aerobic bacteria, each utilizing the major metabolic products of the other. Microalgae grow profusely releasing oxygen from water by photosynthesis. Since at the rapid growth of algae pH can raise to above 9 (because at peak algal activity carbonate and bicarbonate ions react to provide more carbon dioxide for the algae leaving an excess of hydroxyl ions), most pathogens are also killed.

High-pressure membranes are used for nanofiltration and reverse osmosis.

High-rate anaerobic digestion processes involve biomass retention and are characterised by a short HRT but long SRT. High-rate anaerobic biogas reactors are generally used for the anaerobic treatment of heterogeneous wastewaters (e.g. in a DEWATS) with a relatively low TS content (4 to 6 %).

High-strength wastewater means it contains greater amounts of organic components (such as fats, oils, and greases) than residential wastewater. It can also mean the effluent contains large quantities of suspended solids or high amounts of certain chemicals, such as disinfectants. Any or all of these components can interfere with the normal biological processes most onsite sanitation systems use. These characteristics vary from day to day, even from hour to hour, and they can have a major impact on how a biological system performs. The major concern of having high organic loading in wastewater is physical clogging. But high organic load may cause anaerobic conditions leading to odour problems and poor performance.

High-Strength Calcium Hypochlorite

Horizontal learning is an outcome-oriented process that supports the innate human ability to acquire tacit skills through copying the very best of what others do. It is not the traditional top-down learning that takes place in a classroom with a lecturer and students. Much more, people learn from each other by observation, interaction, and
copying. Horizontal learning can hence contribute to promote community empowerment and defends and advances indigenous knowledge.

A horizontal subsurface flow constructed wetland is a large gravel and sand-filled basin that is planted with wetland vegetation. As wastewater flows horizontally through the basin, the filter material filters out particles and microorganisms degrade the organics. Compared to free-water surface flow constructed wetlands, horizontal sub-surface flow constructed wetlands have the advantage of better oxygen transmission reduced risk of mosquito breeding.

Depending of the degree of pollution of used water in households or industry, it can be reused following a multi-use or cascading principle.

Household-Centred Environmental Sanitation (HCES) is a 10-step participatory sanitation planning process conceived by the Environmental Sanitation Working Group of the WSSCC in 2005 in the form of preliminary guidelines. HCES was subsequently field-tested in 7 countries across Africa, Asia and Latin America. The result of this testing phase is a revised 7-step approach called CLUES - Community-Led Urban Environmental Sanitation Planning. New CLUES guidelines, which are easier to use were published by Eawag, WSSCC and UN-Habitat in 2011. Since then, HCES is considered obsolete and is therefore no longer promoted.

Household-level approaches to drinking water treatment and safe storage are also commonly referred to as managing the water at the “point-of-use”. This term or its abbreviation “POU” typically describe the same procedures as other abbreviations derived from household water treatment, like “HHWT” or “HWT” or “HWTS” (The “S” in “HWTS” refers to safe storage). “Household water management” is also commonly used, and can encompass both treatment and storage. All these terms can refer to a variety of treatment procedures, for example, with chlorine or other chemical disinfectants, sunlight or UV lamps, various filters, or flocculation-disinfection formulations.

Household-level approaches to drinking water treatment and safe storage are also commonly referred to as managing the water at the “point-of-use”. This term or its abbreviation “POU” typically describe the same procedures as other abbreviations derived from household water treatment, like “HHWT” or “HWT” or “HWTS”. (The “S” in “HWTS” refers to safe storage.) “Household water management” is also commonly used, and can encompass both treatment and storage. All these terms can refer to a variety of treatment procedures, for example, with chlorine or other chemical disinfectants, sunlight or UV lamps, various filters, or flocculation-disinfection formulations.

Human centred design (HCD) is an innovation methodology to develop appropriate and innovative solutions to problems. It makes no assumptions about potential solutions and does not prescribe them from the outset. Instead, HCD engages with end users to gain insight into their dreams, opportunities, and constraints surrounding a specific problem. HCD then uses those insights through an iterative design process, to identify market-based solutions that maximize the likelihood of adaptation, scalability, viability, and desirability to serve the poor through its holistic co-creation process.

Expertise in managing the employees' life cycle (incl. recruiting, hiring, onboarding, training and firing). 

Human-powered emptying and transport refers to the different ways by which people can manually empty and/or transport sludge and solid products generated in onsite sanitation facilities.

Where there is no or no sufficient supply of fresh or drinking water, nor motorised vehicles to distribute it, water distribution is human-powered. Human-powered water distribution refers to the use of jerry cans and small recipients to fetch water from a centralised distribution point (e.g. river, lake, borehole, shallow well). Either people collect and transport the water themselves or they buy it from mobile vendors that often use small barrels on wheels to transport the water and sell it door-to-door. The effort of ensuring water supply can be high for single families or communities and its price is often higher than that of a well managed public piped distribution system.

Humic acid is a principal component of humic substances, which are the major organic constituents of soil (humus). Humic sub-stances are formed by the microbial degradation of dead plant matter, such as lignin. They are very resistant to further biodegrada-tion. A typical humic sub-stance is a mixture of many mole-cules, some of which are based on a motif of aro-matic nuclei with phenolic and carboxylic substituents, linked to-gether. The functional groups that contribute most to sur-face charge and reactivity of humic substances are phenolic and carboxylic groups. Humic and fulvic acids are commonly used as a soil supplement in agriculture. Organic soil amendments (humus) are beneficial to plant growth due to the release of its constituent nutrient elements into inorganic forms and through its effect on the soil fertility through their water-holding capacity.

Humification describes the process of sludge treatment in planted dewatering/drying beds. The sludge is loaded on the bed and dewatered by percolation in the filter and by evapotranspiration through the plants. The root system of the plants maintains the permeability of the sludge layer. The sludge is be added intermittently. Sludge has to be removed only once every 5 -10 years depending on design. The final product has is very well mineralized and has a soil-like structure. The long solids retention period and pathogen die-off and allows direct reuse of the solids in agriculture. Percolate quality considerably improves by the presence of plant (compared to unplanted drying beds) but may still require a polishing treatment.

The stable remnant of decomposed organic material. It is a dark-brown or black earthen material. Used as a soil amendment in agriculture, it improves soil structure and increases water retention.

Hybrid constructed wetlands combine the high BOD and TSS removal in surface-flow constructed wetlands with the good nitrification due to better oxygen transfer in sub-surface CWs. Depending on the purpose, hybrid wetlands can be either surface flow followed by sub-surface or sub-surface flow followed by surface flow.

Permeability in fluid mechanics and the earth sciences (commonly symbolised k). It is the measure of the ability of a porous material (often, a rock or unconsolidated material) to allow fluids (e.g. water) to pass through it.

The hydraulic gradient is the difference of the height of the water table from one distance to another. The liquid will flow along the hydraulic gradient from where the hydraulic head is highest to where it is lowest by gravity due to the difference in pressure.

The hydraulic head measures the water pressure expressed in terms of height. For instance the pressure on the bottom of a lake filled with a water column of 10 m, will receive a water pressure of 10 m expressed as hydraulic head.

The average amount of time that liquid and soluble compounds stay in a reactor or tank. It is calculated by dividing the volume of a reactor (e.g. m3) by the influent flow rate (e.t. m3/day). In wastewater treatment systems the HRT influence the treatment efficiency and is therefore an important design parameter.

A cyclone separator parts granular solids from a liquid (e.g. river water) by clustering them through centrifugal force.

Hydrogen peroxide (H2O2), a colourless water-like liquid, is one of the most versatile, reliable and environmentally friendly oxidising agents. The relative safety and simplicity of its uses has led to the development of a number of applications in water treatment such as odour removal, disinfection or metal removal. Hydrogen peroxide is also used in advanced oxidation processes (AOP) and can be combined with catalysts or other oxidisers to produce reactive oxygen species (ROS) able to attack a wide range of organic compounds and microorganisms. The production of hydrogen peroxide is usually performed at industrial scale but can also be done directly in drinking water (or pre-treated wastewater) by electrolysis.

Hydrologic is a Social Enterprise legally registered in Cambodia. It produces and markets two ceramic water filters (Tunsai and Super Tunsai) in Cambodia, especially to rural customers. For more information please visit http://www.hydrologichealth.com/

Hydrolysis describes the cleavage of a chemical compound through the reaction with water. Thereby, a hydrogen atom (H) is added to one part of the split chain, while the remaining hydroxyl group of the water (OH) is added to the other. Hydrolysis is the first step of anaerobic digestion in which insoluble complex molecules such as carbohydrates and fats are broken down to short sugars, fatty acids and amino acids.

Hydroponic means the cultivation of plants in water without soil. Nutrients, essential for the growth of the plants are thereby provided from the water.

When the mechanical energy from flowing or falling water is used to produce energy, this is called hydropower.

Hydropower uses the power of moving water (kinetic energy) to generate electricity. Small-scale hydropower produces between 1 and 30 MW. Small-scale hydropower systems can be installed in small rivers, streams or in the existing water supply networks, such as drinking water or wastewater networks. In contrast with large-scale hydropower systems, small-scale hydropower can be installed with little or negligible environmental impact on wildlife or ecosystems, mainly because the majority of small hydropower plants are run-of-river schemes or implemented in existing water infrastructure. Due to its versatility, low investment costs, and as a renewable energy source, small-scale hydropower is a promising option for producing sustainable, inexpensive energy in rural or developing areas.

Hydroxylapatite, also called hydroxyapatite, is a naturally occurring mineral form of calcium apatite with the formula Ca₅(PO₄)₃ but is usually written Ca₁₀(PO₄)₆(OH)₂ to denote that the crystal unit cell comprises two entities. HAP is a natural mineral and demonstrated to be a very effective and biocompatible adsorbent for fluoride removal from contaminated water (MOURABET et al. 2015; MOHAMMAD et al. 2017). Elevated concentrations of fluoride in drinking water are a serious health concern, with dental and skeletal fluorosis being the most commonly reported fluoride-related diseases (FAWELL et al. 2006).

To mitigate the effects of lacking hygiene on health, various approaches have been developed that should help people in improving their hygiene. These approaches include guidelines on how to conceptualise, plan and carry out health and hygiene projects.

Hyperthermophiles are organisms (e.g. bacteria, worms, funghi etc.) that prefer extremely hot environments (80 to 120°C).