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Clay pebblesWater treatment

Application of clay aggregate in Biological Aerated Filter

Since the 1980s, the biological aerated filter (BAF) has received widespread attention and has become a research hotspot at home and abroad. As a new type of high-efficiency biofilm sewage treatment technology, it has good applications in the removal of organic matter in sewage, nitrogen and phosphorus removal, and industrial wastewater treatment.

1. Biological aerated filter (BAF)
1) Biological aerated filter (BAF) – basic principle
The basic principle of BAF is to use granular fillers as the medium to achieve the purpose of removing pollutants in water through the adsorption and interception of biofilms and extracellular polymers attached to the fillers, the oxidative decomposition of microorganisms, and the hierarchical predation of food chains formed along the direction of water flow. The function of denitrification and phosphorus removal is realized by utilizing the existence of aerobic and anoxic regions in the reactor.
2) Biological aerated filter (BAF) – characteristics
BAF features: This technology has the advantages of good effluent quality, short hydraulic retention time, small footprint, low investment and operating costs, strong impact load resistance and convenient management. It is an environmentally friendly, economical, efficient and energy-saving sewage treatment. New technology, which can realize the renewable and sustainable utilization of water resources, is very suitable for the shortage of water resources, insufficient funds, and relatively backward technology in my country’s sewage treatment. We should increase research and development efforts. At the same time, you can view more technical documents on China Sewage Treatment Engineering Network.
3) Biological aerated filter (BAF) – filler
In the biological aerated filter, the filler is the core component, which is extremely important to the treatment effect and operation control of the biological aerated filter. First of all, as the carrier of microorganisms, the filler affects the growth, reproduction, shedding, shape and spatial structure of the biofilm, provides a stable environment for the microorganisms to inhabit and reproduce, and can maintain a large amount of microorganisms; secondly, the filler is the biofilm in the reactor. The place where the biofilm is in contact with the wastewater, and can have a mandatory turbulent effect on the water flow, so that the wastewater can be redistributed; in addition, the filler is used as a medium for removing suspended solids, and its filtration performance affects the biological aerated filter. removal effect.

2. Types and characteristics of biological filter materials
1) Types of biological filter materials
The fillers used in the biological aerated filter can be divided into inorganic fillers and organic polymer fillers according to the different raw materials used.
Commonly used inorganic fillers are: clay aggregate, coke, quartz sand, activated carbon, expanded aluminosilicate, etc.);
Organic polymer fillers include: polystyrene, polyvinyl chloride, polypropylene PE, various resins, plastics (including various foam materials), fibers
2) Characteristics of biological fillers
①Granular filler: This is the earliest filler that has been used up to now, and its material is inorganic clay aggregate or quartz sand. The main characteristics of this type of packing are rough surface, easy to attach organisms, and strong ability to intercept suspended pollutants. The disadvantage is that it has large resistance and is easy to block.
② Irregular granular packing: Raschig ring (RaschingRing) Pall ring (PallRing) in the early days, currently commonly used are Hacketten ball (Hacketten) and multi-faceted hollow ball, etc., which can be made of ceramic graphite, plastic or metal. Simple structure, low price, but uneven fluid distribution;
③Fiberglass or plastic filler: smooth surface, poor biofilm adhesion, easy to age, often prone to clogging in actual use. The water flow in the soft filler is not ideal, and it is easy to produce balls, which greatly reduces the surface area, and then produces anaerobic effect inside the balls, affecting the treatment effect;
④ Activated carbon particles: large specific surface area, many pores, but expensive, and because the surface pore size is too small, most microporous microorganisms cannot be used;
⑤Plastic fiber filler: light weight, hard, but smooth surface, small porosity, not easy to hang film; fiber filler generally has shortcomings such as easy agglomeration and difficult filling;
⑥Honeycomb or corrugated plate packing: the material is usually glass fiber reinforced plastic or plastic (polyethylene polystyrene and polypropylene, etc.), and its main advantages are high void ratio, simple structure, light weight but high strength, good anti-corrosion performance, and aging resistance. The main disadvantages such as the easy shedding of organisms are that the growth and shedding balance of organisms on the surface of the filler is not easy to control, and it is difficult to obtain a uniform flow rate spherical lightweight clay aggregate in the filler;
⑦Spherical lightweight clay aggregate: It is made of clay as raw material, adding appropriate chemical raw materials as expansion agent, and firing at high temperature. It has many advantages that other traditional fillers do not have: high strength, large porosity, large specific surface area, good chemical stability, suitable density, and strong bio-adhesion.

3.Effect of filler on the efficiency of biological aerated filter
1) Influence of filler particle size
The particle size of the filler has an important influence on the treatment efficiency and operation cycle of the biological aerated filter. The smaller the particle size of the filler, the better the treatment effect. Backwashing, and it is not easy to play the role of the deep layer of the filler. Therefore, the selection of filler for the biological aerated filter needs to consider the treatment efficiency and operation cycle of the filter at the same time, and optimize the selection according to the water quality and treatment requirements of the filter.
2) The density of the filler
The density of the biofilter filler is related to the backwash intensity of the biofilter. The greater the density, the greater the backwash intensity, and the greater the energy consumption; therefore, when selecting the biofilter filler, it is necessary to measure the various fillers. Density. Units with waste water that need to be treated can also consult companies with similar sewage treatment experience on the Sewage Bao project service platform.
3) Filling layer height
The height of the filter layer is related to the quality of the effluent. Within a certain range, increasing the height of the filter layer can improve the treatment effect of the filter and ensure the quality of the effluent, but at the same time, the increased sewage lifting head and backwashing intensity will lead to increased energy consumption.

4. A new type of filler – biological clay aggregate
1) Types of biological clay aggregate
① Spherical lightweight clay aggregate: clay (mainly composed of metaaluminosilicate) is used as the main raw material, and appropriate chemical raw materials are added as expansion agents, which are fired at high temperature. The clay aggregate is easy for microorganisms to grow, fast to form a film, and after contacting with nutrients in wastewater, it has a high transfer rate, fast adsorption and oxidation speed, and high treatment efficiency.
② Fly ash clay aggregate: Fly ash clay aggregate is generally spherical, the surface is rough and hard, and there are many micropores in the honeycomb shape. The advantages of fly ash clay aggregate and its products mainly lie in four aspects: excellent performance, good economic benefits, strong construction adaptability and wide application range.
③ Nano-modified clay aggregate: The dispersed phase of nano-powder particles has a large specific surface area and strong interface effect, and is attached to the surface of the clay aggregate filler and the surface of the internal pores to provide high roughness for the film formation and start-up of the reactor, thereby improving Bacterial proliferation rate and biofilm formation rate.
④ Korean EPP filler: The filler is made by mixing polypropylene resin powder and powdered activated carbon in a certain proportion to form a masterbatch containing activated carbon, and then extruding the masterbatch to produce expanded polypropylene filler. Because the filler contains powdered activated carbon, it has strong organic adsorption capacity and porosity suitable for microbial growth.
⑤ Sewage plant sludge and river bottom sludge filler: a new type of sludge filler prepared with sewage plant sludge or river bottom sludge as the main raw material and clay and water glass as additives. Its removal effect on ammonia nitrogen, COD, turbidity, etc. is better than ordinary clay aggregate, meets the requirements of biofilm carrier, and creates another way for sludge resource utilization.
2) Performance indicators suitable for biofilter fillers
The clay aggregate generally used in BAFs is selected based on:
①　The particle size is above 5mm (the smaller the particle size, the more clogged it will be);
②　The bulk density is generally between 500~800kg/m³ (it cannot float on the water surface and depends on the upstream velocity of BAFs);
③　The higher the water absorption, the better;
④　Have a certain compressive strength (above 2.5Mpa);
⑤　The sphericity coefficient is above 0.95;
⑥　Color is not the standard to determine the quality of clay aggregate;
⑦　The specific surface area is preferably 8.0㎡/g (the bigger the better);
⑧　The slag dropping rate is less than 0.5%;
⑨　The soluble rate of hydrochloric acid is less than 1%.

5. Biological sludge clay aggregate
my country has developed the “sludge bio-clay aggregate” production technology, and successfully prepared a new type of biological aerated filter filler – sludge bio-clay aggregate. In the research, it was found that compared with commercial clay aggregate, sludge bio-clay aggregate has the characteristics of high porosity, high specific surface area, and high efficiency of wastewater treatment. In addition, since the sludge contains a variety of trace elements, it can promote the growth of microorganisms very well, so it is easy to form a film, and has higher removal efficiency of nitrogen and phosphorus and COD for industrial wastewater and domestic sewage.
The internal pores of sludge biological clay aggregate are extremely developed, and there are 300-600 μm large pores between the skeletons and 30-50 μm small pores inside the skeletons. The large pores between the skeletons can provide an environment for the growth of anaerobic or facultative microorganisms, and increase the specific surface area of the clay aggregate. The small pores inside the skeleton are basically not connected to the large external space, which mainly plays a role in reducing the weight of the clay aggregate. This kind of sludge biological clay aggregate further proves that it meets the requirements of BAF filler in terms of micro-structure.

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Clover Industrial2023-06-160 Comments
Clay pebblesConstruction

Light weight expanded clay aggregate.

As a new type of environmentally friendly material, clay pebbles (LECA) was mainly used in the construction industry at the beginning. It is a porous and lightweight particle formed by high temperature expansion of clay. It has a series of functions such as heat preservation, heat insulation, fire prevention, and earthquake resistance. Because of its cheap price, with good adsorption and air permeability, it is now widely used in gardening and water treatment and other related fields. It is divided into various models, not only the size of the particles, but also the natural color and color. Colored clay pebbles (LECA) is mainly used for in the decoration industry, it can also be used to fix the root system of hydroponic plants and increase the ornamental value.

clay pebbles (LECA) has the following characteristics:
clay pebbles (LECA) is a light particle after high temperature expansion. Although it contains a small amount of mineral trace elements, it does not contain organic matter and belongs to a sterile matrix. It has a light weight and a porous honeycomb structure inside, which has certain adsorption and air permeability. 80% of its uses are used in the construction industry. In the gardening field, it is generally used to cushion the bottom of flowerpots, act as paving stones, and fix the roots of hydroponic plants, or used to purify and stabilize water quality in fish tanks and aquariums. It is rarely used for soil preparation because it does not contain organic matter and is not easy to decompose. The effect of soil preparation is not as good as medical stone, vermiculite, red jade soil and other mineral particle substrates.

The main role of clay pebbles (LECA) in gardening and home furnishing:
① Act as a paving stone:
The particle size of clay pebbles (LECA) is relatively uniform, the material is light, and the price is very cheap. It can be used as a paving stone to prevent the soil from splashing around when watering, to avoid the floating of light substrates such as coconut peat and perlite, and to prevent the soil from being directly exposed to water. In the natural environment, it can also isolate the peculiar smell of the soil, prevent the breeding of mosquitoes in summer, and increase the ornamental value of potted plants.

② Cushion the bottom of the flowerpot:
Using clay pebbles (LECA) to cushion the bottom of the flowerpot can play the role of a hydrophobic layer, which saves soil and breathes air. When potting or changing potted plants, you can first spread a layer of clay pebbles (LECA) on the bottom of the pot, which can not only save nutrient soil, but also prevent the soil from losing from the bottom hole of the pot when watering, and at the same time protect It can prevent water accumulation in the pot and increase the air permeability of the root system.

③ Hydroponic flowers:
When growing hydroponic plants or carrying out soilless cultivation (hydroponics), spread a layer of colored clay pebbles (LECA) on the bottom of the hydroponic container, which can not only fix the root system, increase the oxygen content of the root system, but also purify the water quality, and at the same time let the single water Cultivated plants look more aesthetically pleasing.

④Purification of water quality in fish tanks and grass tanks:
The porous structure of clay pebbles (LECA) honeycomb has a certain degree of adsorption, so it has the function of purifying and stabilizing water quality and can be used as the bottom sand of fish tanks and grass tanks. However, it should be noted that the clay pebbles (LECA) used in the aquarium belongs to clay pebbles (LECA) sand, the particles are relatively small, and the material is heavier than ordinary clay pebbles (LECA), and it will not float on the water surface, but it needs to be cleaned many times before use. of dust.

As a high-quality granular matrix, clay pebbles (LECA) not only exerts its unique advantages in the construction field, but also exerts its waste heat for the gardening family. You can choose the specific particle size and color according to your actual needs.
Suggestion: Use 3-5 mm small particles for paving, 5-8 mm large particles for the bottom of the flowerpot, colored clay pebbles (LECA) for hydroponics, and special clay pebbles (LECA) sand for aquariums. As for growing flowers with soil, it is better to use peat, perlite, and coconut peat. These three most commonly used substrates can be mixed together, so that most of the potted plants can be used universally.

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Clover Industrial2023-06-150 Comments
Clay pebblesConstructionPlanting

Lightweight expanded clay aggregate suppliers, Properties Analysis

Lightweight expanded clay aggregate supplier

Lightweight expanded clay aggregate is a relatively popular material. It can not only be used to plant plants and flowers, but also can be used to backfill buildings, so its performance is still good. So, what about the specific performance of clay pebbles? The editor of clay pebbles will take you to understand it together today.

Specifc performance in constuction

First of all, the frost resistance of clay ball is very good, which can be regarded as a great advantage of it! The main reason is that it has good anti-permeability, so clay pebbles is used for construction in winter, which is relatively reliable. On the other hand, its earthquake resistance is also good. After the earthquake, many buildings collapsed, but the LECA balls building is still very complete, so it is relatively earthquake-resistant, so it should be widely used. People love it There is also a reason.

Hard, not easily broken

In addition to the above two properties, there is another point, that is, the performance of leca aggregate is stable and will not easily deteriorate. This is very practical, because it can be used for a long time!

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Clover Industrial2023-06-020 Comments
Clay pebblesConstructionPlanting

Detailed performance introduction and application of clay pebbles

1. Scope of application: heat insulation and slope finding of the roof; backfill and cushion of the ground, toilet and kitchen; greening of the roof garden; soil-less cultivation; sewage treatment, etc.

Summary: The heat insulation effect of slope finding is obvious, the roof can bear load, and the construction is convenient; the backfill cushion layer has a good water absorption effect and reduces the load on the floor; the roof greening keeps water and soil loss away, and quickly dredges the accumulated water; soil-less cultivation is clean, environmentally friendly, and energy-saving; Filter sewage impurities and absorb harmful substances.

2. Earthquake resistance: light weight, low elastic performance, good deformation resistance, and play a great role in the earthquake resistance of buildings.

3. Fire resistance: When choosing fireproof materials, cement is generally used more, but the fire resistance of clay pebbles is more than 4 times that of cement. It is a new material integrating heat preservation, heat insulation, frost resistance and waterproof.

4. Small density and light weight: From the appearance, the appearance is strong, but there are many small holes inside, because these small holes make it have the characteristics of heat preservation, heat insulation, breathability and water absorption. Because it has honey nest-like micro-pores inside, it is formed by the gas being wrapped into the shell, which is the main reason for the light weight of clay pebbles.

The role of clay pebbles in construction: Now clay pebbles concrete has been widely used in some industrial and civil projects, such as toilet backfill, various types of prefabricated components, cast-in-place concrete, including roof slopes in some places, etc. clay pebbles, because clay pebbles is really a good new material.

Clay pebbles is not only a building material, but can also be used as a filter material. Now many factories are using clay pebbles as a filter material for industrial wastewater treatment, because it not only has a good water absorption effect, but also has a filtering effect. The main reason is that it can be used repeatedly, reducing costs, simpler, more convenient, and more environmentally friendly. Unexpectedly, it has the effect of removing iron and manganese, which is especially suitable for the purification of underground deep water removal of iron and manganese.

Don’t use the previous ideas to make some time-consuming, labor-intensive, expensive, and unguaranteed materials. clay pebbles is really a good choice!

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Clover Industrial2023-06-020 Comments
Clay pebblesPlanting

Can clay pebbles grow all flowers?

Everyone knows that clay pebbles are a kind of high-temperature-fired light weight expanded clay pebbles, which is a material often used in construction. It is generally red in color, very light in weight, and has excellent air permeability, so it is suitable for planting flowers.

However, it seems that not all flowers can be planted with clay pebbles! Be sure to pay attention to distinguishing.

On the other hand, clay pebbles can also drain water, because its interior is full of tiny pores, which can retain water and keep flowers fertile. But it also puts forward certain requirements for flowers. Only flowers or plants such as orchids that have high requirements for air permeability and water permeability can be cultivated with clay pebbles, otherwise it is not feasible.

And the granular sizes of clay pebbles need to be noticed too, and do not use it indiscriminately. If the roots are relatively slender, you should choose smaller clay pebbles for cultivation.

What are the differences between high-quality clay pebbles and inferior clay pebbles?

Because high-quality clay pebbles are fired from high-quality clay, it is non-toxic, non-radiative, safe and pollution-free. In nature, high temperature resistance, corrosion resistance, sound insulation and heat insulation. However, inferior clay pebbles are sintered clay pebbles produced by granulation and roasting after municipal solid waste treatment, which has poor water absorption and air permeability and pollution.

So, when buying, we must keep our eyes open and choose high-quality clay pebbles.

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Clover Industrial2023-06-020 Comments