Generally, the most significant microbiological problems in water systems are biofilms — the slimy precipitates that form on the inner surfaces of pipes — and the stagnancy of water in pipe systems. The structure and materials of piping have a huge effect on the formation of biofilms and the quality of water. Biofilms often form, and Legionella bacteria (to give one example) often multiply, in pipes where the flow of water is small or non-existent due to the complex and branched structure of the piping network, or the irregular use of this network. Microbes may emerge from the biofilm, e.g. due to a burst of pressure, and from there, they may pass into the water used by the consumer. From the standpoint of water quality, it is quite important to run the water until it is cold before using the water for drinking or food preparation.
The household water system of a premises must be designed in such a way that the system does not have components in which the water remains stagnant. The temperature of a water system’s cold water must remain under 20 °C everywhere in the system, and the temperature of the warm water must be above 55 °C. All components of the system must be approved for use with household water, and must be suitable for the quality of the area’s raw water. The system must also be designed in such a way that no harmful pressure buildups occur there. The household water system of a premises can be supplemented with various solutions and devices that allow further improvement of the water quality. For example, using electronic faucets, it is possible to program the automatic running of water through parts of the system that are at risk of water stagnation. It is also possible to connect devices to the system, or a part of the system, that provide extra purification — e.g. a UV device that kills microbes. The heating- and cooling devices of a premises must not cause hygiene risks, either. The piping and other components of a household water system may also be produced with antimicrobial material.
In North Europe, cold water delivered to tap is drinkable in every household. This is achieved due to three main reasons: 1. Availability of high-quality raw water sources. 2. Local water treatment utilizes advanced technologies. 3. Excellent geographical coverage of delivery network, where delivery systems are built from standardized materials.
Raw water is either surface water or ground water. In many cases, especially when surface water is used it is purified in waterworks before delivered to households. Quite often groundwater is drinkable as such.
When well water is used as a raw water source sometimes own domestic systems are utilized. These include alkalinity and pH control with limestone alkalization devices. In some cases, raw water might contain too much calcium and the use of water softeners is additionally needed. In order to decrease scaling and corrosion in drinking water systems magnetic water treatment techniques has been developed and utilized.
Pipes and pipe systems are used to transport drinking water to the taps and wastewater to sewer. In tap water systems in Europe and specially in the Northern Europe (Finland, Sweden, Norway, Denmark, Germany) tap water is also used to drinking and the quality of water is hygienically and microbially safe to drink. In order to have safe drinking water from the tap the water is treated at the waterwork and the material of the pipes and pipes system is valid to be in contact with drinking water. If water is not used in drinking, the quality of the water is needed to be good enough to washing.
In drinking water different materials can be used. In Finland the most used materials are PEX (plastic pipe), copper and composite (combining plastic, usually PEX or PERT, and aluminium)
To keep the water system hygienic there are few points to remember
The temperature of water is important. Keep the temperature of the cold water below 21 °C (recommendation in Finland) and the hot water over 55 °C to avoid legionella in the water system.
Wastewater treatment is a process used to remove contaminants from wastewater or sewage and convert it into an effluent that can be returned to the water cycle with minimum impact on the environment, or directly reused. Water treatment usually takes place in the waterworks. Several different purifications steps that utilize novel technologies are used. These include filtrations (screens and sand filters), flotation and sedimentation steps assisted with chemical coagulation and flocculation as well as chemically controlled disinfection, pH and alkalinity levels. In some special cases also microfiltration, ultrafiltration and reverse osmosis technologies are used.
A wastewater treatment process usually combines preliminary treatment such as screening and secondary treatment for nutrients (P, N) and organic matter (BOD) removal. Typical secondarary treatment is activated sludge process containing in series i.e. aeration tank, sedimentation tank. Hygienization (or disinfection) can be added as a tertiary treatment to the process. It can be done with chemical (peracetic acid, chlorine) or with UV. The need for pre-treatment of hospital wastewater has been subject of some studies, but it is not routinely done in hospitals yet due to the lack of disposal requirements for drug residues in wastewater.
In addition, decentralized wastewater systems that convey, treat and dispose or reuse wastewater from small communities, buildings and dwellings in remote areas, individual public or private properties are used in some extent. Wastewater flow is generated when appropriate water supply is available within the buildings or close to them. Decentralized wastewater systems treat, reuse or dispose the effluent in relatively close vicinity to its source of generation. They have the purpose to protect public health and the natural environment by reducing substantially health and environmental hazards. They are also referred as “decentralized wastewater treatment systems” because the main technical challenge is the adequate choice of a treatment and/or disposal facility.
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