2.1.2. Basic elements of settlement sewerage. System and schemes of sewerage

Providing of proper sanitary state of settlements and industrial enterprises possible only during organized gathering and well-timed deleting beyond the borders of their territory of sewer water with further clearing and disinfection.

Sewerage of settlement is a complex of engineering structures and equipment, that are intended for a reception and transportation of sewer water to the clearing structures. Plan of object, that is equipped with sewerage, with drawn on it elements of sewerage system, is named the scheme of sewerage. Scheme of sewerage of settlement is formed from such basic elements: internal sewerage equipping of buildings and structures, courtyard and street sewerage network, collectors, sewerage pump stations and pressure pipeline, clearing structures and throwing of cleared sewer water into reservoirs.

Internal sewerage equipment is intended for receiving of sewer water and removing of it beyond the borders of building. In dwelling and public buildings the receivers of sewer water are the sanitary instruments. At the industrial enterprises for the receiving of sewer water can be used special receivers in form of carters, ladders, trays, which are installed directly near apparatus and technological equipment.

Street sewerage networks – a system of underground pipelines, which receive sewer water from courtyards (blocks) networks and intended for transportation of sewer water in borders of settlement. Sewerage networks are built mainly as self-flow by laying them due to relief of locality. During this the territory is divided into pools of the sewage system. Pool of the sewage system is a part of territory that is equipped with sewerage and is bounded by watersheds.

Sewerage networks, which are intended for removing of atmospheric water, are named rain networks, or gutters; networks, which are intended for removing of domestic water, - domestic; networks for removing of industrial sewer water, - industrial. Networks are also created for joint removing of different types of sewer water (domestic-industrial, industrial-rain, etc.).

Street sewerage networks in borders of each pool are connected by one or several collectors. Collector is sewerage pipeline, which collects sewer water from two or several street networks.

During considerable deepening of self-flow sewerage pipelines, pump stations of raising and pumping-over of sewer water are arranged. Sewerage pump stations are subdivided into local, region and main. Local pump stations serve for

pumping-over of sever water from one or several buildings, region – for pumping-over of sewer water of regions and pools. Main pump station swaps all sewer water onto clearing structures.

Clearing structures are those which intended for clearing and disinfection of sewer water and the recycling of its sediment. Content of clearing structures can be different and depends on method of clearing and type of sewer water. Clearing structures are located lower down stream relatively the settlement or industrial enterprise, which equipped with sewerage.

After clearing and disinfection the sewer water through special devices, which are named outputs, is thrown into reservoir.

Depending on the way of removing of some types of sewer water – together or separately – systems of sewerages are divided into general-flowing, separated (full or incomplete) and semi-separated. Type of sewerage system of town is chosen on the basis of comparing of technical-economic and sanitary-hygienic indexes.

At general-flowing system (fig. 2.1a) all types of sewer water are drained to the clearing structures through single sewerage network.

Separated sewerage system is those one, at which separate types of sewer water with contamination of different character are drained by independent sewerage networks (fig. 2.1б). Separated sewerage systems in their turn are divided into full and uncompleted. Full separated sewerage system foresees not less than two networks: one – for receiving and draining of domestic and close to them by content industrial sewer water onto the clearing structures; another – for receiving and throwing into the reservoir of atmospheric and conditionally clean industrial sewer water.

Incomplete separated system foresees draining of domestic sewer water by closed network onto the clearing structures and unorganized draining of atmospheric water to reservoir. Such decision decrease the simultaneous capital charges and allows in the future with the completion of networks to transfer to the total separated sewerage system, which from the sanitary point of view is enough reliable.

Semi-separated (fig. 2.1в) is named those sewerage system, at which at the places of intersection of independent sewerage networks for draining of different types of sewer water the sluice-way chambers are installed, that allow to transport the most contaminated rain water at low expends in domestic network and to drain it through general collector onto clearing structures, and during thunderstorms – to throw comparatively clean rain water directly into reservoir.

In our country is mainly used incomplete separated sewerage system as the first part of construction. In general the sewerage system is chosen with recognition of local conditions, technical-economic indexes and sanitary-hygienic requirements. In sanitary relation the most expedient is the general-flow sewerage system, at which all sewer water is subjected to clearing. However, this system

needs considerable capital and exploitation expends, as substantially increase the sizes of clearing structures, communications and capacity of equipment. Besides this, the structures work with full capacity only during big thunderstorms during reception of all atmospheric water mass onto clearing structures. For decreasing of cost of general-flow network, on the collectors along reservoirs the thunderstorm flushes are installed. Such decision decreases sanitary reliability of general flow sewerage system and allows hitting of diluted but unrefined domestic sewer water into the reservoir. From sanitary point of view the semi-separated sewerage system has a bit higher reliability. Unrefined sewer water don’t get into the reservoir in this case, but cost of this system isn’t lower than of general-flow, that caused limited spreading of semi-separated sewerage system.