Sludge sites of wastewater treatment plants. Sludge bed Stages of wastewater treatment
One of the oldest and most proven methods for recycling sediments formed in primary settling tanks, digesters, and two-tier settling tanks is sludge pads, and it is also the simplest and cheapest method. The sites are also used for other types of precipitation, the main thing is that their humidity is greater than 90%.
Sludge beds can be designed:
- With natural base;
- With drainage system;
- Without drainage system;
- WITH surface drainage water;
- As compaction pads.
Sludge beds on natural basis- This is a piece of land specially planned in the form of several areas, which are called maps. Each site is fenced with an earthen berm on all sides (but an entrance for vehicles can be arranged on one side). A system of supply pipes is organized at the site, through which raw sludge or activated sludge is periodically supplied evenly over the area. It is dried to a humidity of about 75-80%. After which the “dry sludge” is loaded onto a vehicle or trolley and transported to landfills or for further processing. Silt water seeps through the ground. There are two options for collecting sludge water:
- If the soil under the sludge beds does not have sufficient filtering properties, then a drainage system is installed. It consists of pipes located in ditches, covered with gravel or crushed stone. Such ditches are installed at a depth of more than 0.6 m. Silt water is most often sent to the beginning of the treatment plant.
- If the soil under the sludge beds has good filtering abilities (sand, loam, sandy loam), then drainage may not be necessary. But only if the sludge water is not dangerous from a sanitary point of view and the groundwater is located at a depth of 1.5 m, otherwise a decrease in its level is required.
Types of sludge beds
It is recommended to design sludge beds with surface water drainage in areas with an average annual temperature of 3-6 0C and precipitation up to 500 mm/year. Such sludge platforms are made in the form of a cascade of maps located at different height levels. The sludge is fed to the highest card; as it dries, it is discharged down through bypass-wells. Sludge water is discharged from the bottom card into the primary settling tank.
Sludge compaction platforms are reservoirs (usually reinforced concrete with a monolithic bottom), with a depth of 2 m.
Calculation of sludge beds
Calculation of sludge beds involves determining the dimensions of the maps, rollers, slopes and pipeline diameters.
The area of silt maps depends on the volume, structure of sediment, climatic conditions and the type of soil that serves as the base. IN general view it is calculated by the formula:
S = (Vο 365)÷(a b C)
Where, Vo– sediment volume, t/day; a– coefficient adopted to take into account the reduction in sludge volume due to its disintegration during fermentation (reference value and depends on the type of structure from which the sludge is received); b– coefficient adopted to take into account the decrease in volume due to loss of moisture; WITH– load on sludge beds (reference value and depends on the design of the sludge bed, climatic conditions, type of sediment), m³/m².
The sufficiency of the area obtained by calculation is checked by the freezing condition in winter period. To do this, calculate the height of the frost layer:
Hus = (W t K2)÷(S K1)
Where, W– volume of sediment per day, m³; t– freezing period, days; S– useful area of cards, m²; K1– part of the useful area of the sludge platform allocated for freezing, m²; K2– coefficient taking into account filtration and evaporation.
The dimensions of the map are taken based on the aspect ratio of 1:2 or 1:2.5. Number of cards – at least 2.
The height of the rollers is taken from 0.3 m, their slope depends on the soil.
The slope of the drainage network is assumed to be 0.003, and that of the supply network is 0.01-0.03.
Operation of sludge beds
Operation of sludge sites involves monitoring the condition of distribution, outlet, supply, drainage pipes, the condition of the rollers (for collapses and other types of deformation), humidity and chemical composition sludge (supplied and discharged) and its timely removal. Dried sludge is collected manually with shovels into trolleys that move along rollers (for small stations), manual loading, peat and manure loaders onto vehicles, scrapers, bulldozers (for medium and large stations).
During the operation of wastewater treatment plants, sludge is formed that must be dewatered. Sludge beds are used for this purpose. They are quite easy to use, but are extremely dependent on climatic factors.
The dependence of sludge beds on climatic conditions must be taken into account during design in order to ultimately obtain dehydrated sludge with the required humidity.
The sites are divided into two categories – natural dewatering and intensive dewatering. In the first case, evaporation and decantation are used - processes similar to those that occur in natural natural environment. This type includes compaction sites and structures with surface drainage.
At intensive dehydration sites, processes that differ from natural ones occur. In this case, the factors of the natural cycle are modified. Structures of this type can be equipped with artificial drainage or a waterproof coating, as well as heating. The choice of sludge sites for wastewater treatment plants, as a rule, depends on several conditions - climate, free space, and access to additional power sources.
Natural dewatering sludge beds are compacted and sludge water is removed, which is subsequently dried.
Sludge beds perform an important function - treatment of sludge from wastewater treatment plants.
How to increase the productivity of sludge beds at wastewater treatment plants?
There are several methods for optimizing the productivity of sludge beds:
- Compaction of sludge before delivery to sites
- Mechanical tedding and removal of dried sludge from sites
- Conditioning of sludge before it reaches the site
- Blowing air through sludge during processing
- The use of vacuum systems to speed up filtration activities
- Heating of sludge on sludge beds
Sludge pad sewerage treatment facility for dewatering sludge (sludge) falling from Wastewater when they are settled or rotted in the Digester tanks. The main part of the structure is graded plots of land (platforms) surrounded by earthen ramparts through which silt gutters pass to supply sediment. Raw sludge from settling tanks or fermented sludge from digesters or other structures is periodically accumulated in a small layer on an industrial site and dried, as a result of which the water content in it decreases by 20-25%, it acquires the structure of wet earth and is then transported as fertilizer to the landfill. .-X. land. I. p. are usually arranged on well-filtered natural soils(sand, sandy loam) or on artificial foundations with drainage of structures (See Drainage of structures).
Big Soviet encyclopedia. - M.: Soviet Encyclopedia. 1969-1978 .
See what “Sludge platform” is in other dictionaries:
Sewage treatment facility for dewatering sludge (sludge) falling out of wastewater (during its settling) or rotting in digesters; flat area land (up to several hundred m²), fenced with earthen rolls along which... ... Big Encyclopedic Dictionary
sludge bed- 3.3 sludge platform: Technological structure designed for dewatering sewage sludge in natural conditions, equipped and operated taking into account environmental safety. Source: GOST R 54535 2011: Resource conservation.… …
Sewage treatment facility for dewatering sludge (sludge) falling out of wastewater (during its settling) or rotting in digesters; a flat piece of land (up to several hundred square meters), fenced with earthen rolls, along... ... encyclopedic Dictionary
A structure for dewatering sludge (sludge) falling out of wastewater or rotting in digesters; basic part of the planned structure plots of land (platforms) surrounded by earthen ridges, along the Crimea there are trays for supplying sediment. Fermented... ... Big Encyclopedic Polytechnic Dictionary
silt platform- Sewage treatment facility for dewatering sludge (sludge) falling out of wastewater during settling or rotting in digesters. Note The main part of the structure is planned plots of land (sites), surrounded by earthen ... ... Technical Translator's Guide
A structure for drying sewage sludge and silt, consisting of a planned area of land surrounded by ramparts (Bulgarian language; Български) basin behind mud ( Czech; Čeština) kalove pole ( German; Deutsch) Schlammtrockenplatz;… … Construction dictionary
GOST R 54535-2011: Resource conservation. Sewage sludge. Requirements for placement and use at landfills- Terminology GOST R 54535 2011: Resource conservation. Sewage sludge. Requirements for placement and use at landfills original document: 3.3 sludge platform: Technological structure designed for dewatering sewage sludge... ... Dictionary-reference book of terms of normative and technical documentation
GOST R 54534-2011: Resource conservation. Sewage sludge. Requirements for use for reclamation of disturbed lands- Terminology GOST R 54534 2011: Resource conservation. Sewage sludge. Requirements when using disturbed lands for reclamation original document: 3.5 biological stage of land reclamation (biological reclamation): Stage... ... Dictionary-reference book of terms of normative and technical documentation
Complex engineering structures in the sewerage system (See Sewerage) of a populated area or industrial enterprise, designed to purify wastewater from the contaminants it contains. The purpose of treatment is to prepare waste... ... Great Soviet Encyclopedia
IL, ah, husband. Viscous sediment from mineral or organic matter at the bottom of the reservoir. | adj. silty, oh, oh. Sludge site (sewage treatment plant). Dictionary Ozhegova. S.I. Ozhegov, N.Yu. Shvedova. 1949 1992 … Ozhegov's Explanatory Dictionary
Sludge beds used for dewatering sediments are planned land, divided into maps by earthen ridges (Fig. II 1.36).
The sludge with a moisture content of 90-97%, most often 97% (fermented sludge from digesters), is periodically poured into separate cards measuring (10...40) X (60...120) m and dried. The height of the sediment layer dropped onto the card at a time is 0.2-0.25 m. The dried sediment has a moisture content of 75-80%.
Sludge beds are usually arranged on a natural foundation at a depth groundwater at least 1.5 m from the top of the cards. If there is not enough territory, as well as when groundwater occurs at a depth of less than 1.5 m, tubular drainage is installed on the sites. The pipes are laid in ditches filled with crushed stone or gravel with a particle size of 2-6 cm. The distance between drainage ditches taken equal to 6 -8 m. Minimum ditch depth 0.6 m, slope 0.003.
The dried sediment is used as fertilizer. A scraper or bulldozer is used to collect sediment. The collected sediment is loaded into vehicles using an excavator. IN winter time The frozen sediment is broken into blocks and taken to the fields.
Rice. III.36. Sludge beds
The dimensions of the sludge beds are determined depending on the amount of sediment introduced, its characteristics (raw or fermented) and climatic conditions. The rate of sediment load per 1 m 2 of area depends on the type of sediment, climatic conditions, the presence or absence of drainage and averages 0.8-2 m 3 per year. The actual area is assumed to be 20-40% larger than the useful one, since part of the area is needed for the construction of roads, rollers and ditches.
In winter, the sediment is frozen, and 80% of the area is allocated for freezing, and 20% is intended for use during the spring melting of the frozen sediment. The height of the frost layer should be 0.1 m less than the height of the enclosing rollers.
For treatment plants with a capacity of more than 10,000 m 3 /day, sludge platforms are arranged with settling and surface removal of sludge water in the form of a cascade of ponds, where sediment is compacted and the released sludge water is removed from the surface. Cascade silt ponds have 4-7 stages. Each stage contains 4-8 cards. Effective area one card is 0.25-1 hectares. The width of the card is taken to be within the range of 30-80 m, length 80-160 m. The height of the fencing rollers is up to 2.5 m.
The released sludge water is collected and pumped to treatment facilities. The amount of sludge water is 30-50% of the volume of dewatered sludge.
It is also possible to install sludge compaction platforms - tanks with a waterproof bottom and walls with a working depth of up to 2 m. The separated sludge water is removed through holes blocked by gates, which are located in the walls at different heights.
The simplest and most common way of dewatering sludge is to dry it on sludge beds with a natural base (with or without drainage), with surface water drainage and on compaction pads.
The first are planned plots of land (maps), surrounded on all sides by earthen ridges (4.60). Raw sludge from sedimentation tanks or fermented from digesters, two-tier sedimentation tanks or other structures, having a humidity of 90% (from two-tier sedimentation tanks) to 99.5% (unfermented activated sludge), is periodically poured in a small layer onto areas and dried to a humidity of 75-80% .
Moisture from the sediment partially seeps into the ground, but most of it is removed by evaporation. The volume of sediment decreases. The dried sediment takes on the structure of wet soil. It can be picked up with a shovel and loaded into trolleys and dump trucks for transportation to the place of use.
Silt pads on a natural foundation without drainage are used in cases where the soil has good filtering capacity (sand, sandy loam, light loam), the groundwater level is at a depth of at least 1.5 m from the surface of the map, and seepage drainage water can be released into the ground under sanitary conditions. At a shallower depth of groundwater, it is planned to lower its level.
If the soil is dense and poorly permeable, the sites are equipped with tubular drainage laid in ditches filled with crushed stone and gravel. The distance between drainage ditches is recommended to be 6-8 m, the initial depth of the ditch is 0.6 m with a slope of 0.003.
At small treatment plants, for ease of operation, the width of individual cards is taken to be no more than 10 m. At medium and large stations, the width of cards can be increased to 35-40 m. The sizes of cards should be assigned taking into account the placement of sediment released at a time with a layer thickness in summer 0.25-0.3 m and in winter 0.5 m.
The cards are separated from each other by protective rollers, the height of which is 0.3 m above the working level.
Additional information on sewerage:
INSPECTION WELLS AND CONNECTING CHAMBERS
DIFFERENCE WELLS
LLC DESIGN PRESTIGE
The sediment is distributed over the cards using pipes or wooden trays, laid mostly in the body of the separating roller with a slope of 0.01-0.03 and equipped with outlets.
Sludge areas must be promptly cleared of dried sediment. At small treatment plants, sludge is manually loaded into machines and transported to nearby collective and state farms for use as fertilizer.
Sometimes narrow-gauge tracks for trolleys are laid on the dividing rollers, on which the sediment is transported outside the area and unloaded into cars there.
In winter, frozen sediment is split into separate blocks by special machines, which are then transported to collective farm fields.
At medium and large stations, scrapers and bulldozers are used to remove sediment. The waste collected in dumps is loaded into vehicles using a peat or manure loader mounted on the base of the DT-54 tractor, or a multi-bucket loader. The latter is the most economical of the mechanisms used - its productivity is up to 40 m3/h.
In areas with an average annual air temperature of 3-6 ° C and an average annual precipitation of up to 500 mm for wastewater treatment plants throughput more than 10,000 m3/day, it is recommended to arrange sludge platforms with settling and surface drainage of sludge water. Figure 4.61 shows sludge platforms of this type built at the Kuryanovskaya aeration station. Sludge platforms with surface drainage of sludge water are designed in the form of several (4-7) independently operating cascades. Each cascade consists of four to eight cards arranged in stages. The discharge of sediment from the supply pipelines is provided onto the upper cards. As you accumulate upper layer silt water (or sediment) is discharged to the underlying map through reinforced concrete bypass-wells. The settled sludge water from the lower map of the cascade is pumped into the primary settling tanks of the treatment plant, since the content of suspended solids in it can reach 1.5-2 g/l. The volume of settled sludge water is 30-50% of the volume of dewatered sludge, the humidity of which is reduced from 97 to 94-95%. Further dehydration of the sludge occurs due to the evaporation of moisture from the surface of the sludge.
The useful area of one map is taken to be 0.25-1 hectares with a width to length ratio of 1: 2-1: 2.5.
Sludge compaction pads developed by the Soyuzvodoka-nalproekt Institute together with the Department of Sewerage LISI. The sites consist of rectangular tanks with waterproof bottoms and walls. The walls are constructed from prefabricated reinforced concrete unified panels 2.4 m high, the bottom is monolithic. Working depth of the site is 2 m.
If there is not enough space to set up open sludge areas, then sometimes covered sludge areas are built like greenhouses, covering them with glazed frames. Such sites were built in Kislovodsk. According to experimental data, the annual load on them is 9-10 m3/m2 when drying sediments from digesters.
The area of sludge sites depends on the volume of sediment, the nature of the soil on which the site is located, climatic conditions, as well as the structure of the sediment.
When designing sludge beds with surface drainage of sludge water, the load is assumed to be 1 m3/m2 per year.
Sludge compaction sites are calculated according to the load q, which depends on the working depth of the site and the number of unloadings per year, taken depending on the properties of the sediment and climatic conditions from 1 to 5.
It is necessary to check the sufficiency of the area obtained in the calculation, taking into account the freezing of sediment in winter. Long lasting! The period during which freezing occurs is determined by the number of days with an average daily temperature below -10° C. Part of the moisture (25%) is filtered and evaporates in winter. 80% of the surface of the sludge pads is allocated for freezing, and 20% is left for use during the spring thaw.
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