KR102488233B1 - Method for Reduction of Waste Sludge - Google Patents

Abstract

The present invention relates to a method for reducing wastewater sludge generated in a wastewater treatment plant. More specifically, quicklime (CaO) is added to the sludge of the flocculated sediment produced by centrifuging the sludge of the flocculated sediment produced by adding a coagulant and activated sludge to the wastewater and heated to obtain a slaked lime (Ca(OH) ₂ ) reaction. It relates to a wastewater sludge reduction method comprising a first step of dewatering the sludge of the flocculated sediment into a cake, and a second step of heating and pulverizing the dehydrated sludge cake into particles. In addition, the present invention can safely treat the methyl and sulfa odors generated by the sludge quicklime reaction by passing through the existing water scraper, acid-alkali treatment facility, or electric precipitator or boiler tube to collect and reduce these gases.

Description

Method for reduction of waste sludge {Method for Reduction of Waste Sludge}

The present invention relates to a method for reducing waste sludge generated in a wastewater treatment plant. More specifically, quicklime (CaO) is added to the waste sludge and heated to cause a slaked lime (Ca(OH) ₂ ) reaction to cause a first step in which the sludge of the flocculated sediment is dehydrated into a cake, and the dehydrated sludge cake is heated. And it relates to a method for reducing wastewater sludge comprising a second step of pulverizing into particles. It is effective when calcium chloride is mixed with quicklime in the first and second steps.

In the above, the filtrate of the waste is discharged according to the wastewater treatment standard, and the sludge dehydrated in the first step is reduced by evaporation of water due to the exothermic reaction of quicklime. Heating and crushing in the second stage allows the sludge to be granulated and used as a soil fertilizer or soil improver.

Waste sludge is generated by chemically treating and reacting raw wastewater with inorganic alkaline and acidic coagulants, and then biologically treating and reacting with aerobic or anaerobic microorganisms and centrifuging. On the other hand, the filtrate is discharged in accordance with the wastewater treatment standards for heavy metals, Biological Oxygen Demand (BOD) and Chemical Oxygen Demand (COD). However, in wastewater sludge, filtrate by-products are produced during fermentative production of food or food additives containing carbohydrates, proteins, fats, minerals or vitamins, or filtrate by-products are produced according to the blending or processing of these raw materials. Waste sludge, which is a filtrate, has no proper treatment method, so it is entrusted to a waste treatment company and paid tens of thousands of won per ton, and is burned in an incinerator within the framework of the Environmental Conservation Act or landfilled in an idle land.

In particular, as meat consumption increases, domestic cattle, pigs, and chicken slaughter rates are steadily increasing, and in particular, chickens increased by about 50% compared to 2003. In particular, waste generated from the slaughtering and meat processing processes is rapidly increasing in proportion to the increase in slaughtering quantity. It is expected to reach about 140,000 tons in 2015. Currently, most of the waste is consigned, but due to strengthened environmental regulations and increased energy costs, the cost of consignment treatment per ton increased from 60,000 won/ton in 2015 to 120,000 won in 2020, a 100% increase in 5 years, placing a huge burden on breeding farms. there is.

Wastes generated from food, livestock, and meat processing processes have high organic matter content, so most of them are firstly treated by themselves, and then wastes are treated secondarily by environmental companies, which is a cost burden.

Comparison of treatment items by waste division food waste livestock manure waste slaughtering waste TS (mg/L) Total Solids 190,000 46,300 49,690 VS (mg/L) volatile solids 154,300 32,000 42,420 COD Cr (mg/L) 206,100 60,400 85,900 BOD5 (mg/L) 138,300 34,500 60,120 TN (mg/L) 3,600 3,500 3,600 VS/TS (%) 81 69 85 BOD/COD (%) 67 57 70 Organic matter removal rate (%) 80 68 83 Methane production (tons/waste) 84 13 25

Odor substances generated during exothermic reaction of waste Odor Substances (ppm) Hydrogen sulfide (H ₂ S) Ammonia (NH ₃ ) Methyl mercaptan (CH ₃ SH) 100 non-detection 6 Odor Substances (ppm) Acetaldehyde CH ₃ CHO Styrene Monomer C ₆ H ₅ CH=CH ₂ trimethylamine
(CH ₃ ) ₃ N 2 8 non-detection

From the above table, it can be seen that the concentration of environmental pollution factors (TS, VS, COD, BOD, TN) by waste is the highest in food waste, followed by slaughtering waste and livestock manure waste in order of concentration. Therefore, efficient treatment of these wastes can reduce the environmental cost burden of industries. This is closely related to related industries and national competitiveness.

Solid carbon production technology for reducing and fueling organic sludge (2005.03 ∼ 2007.02, Pittsburg Coal Conference, Industrial & EngChem. Research) Pre-treatment technology for high-moisture biomass gasification (2007.10 ∼ 2010.09, Journal of the Waste Society, Journal of the Korean Society of Environmental Engineering, UKC conference, ISWA conference) Development of high-calorie solid fuel production and biogas production efficiency increase technology from livestock manure (2009.04 ∼ 2011.03, Journal of the Monthly Environment 21 Waste Society Journal of the Korean Society of Environmental Engineering) Food waste treatment and excellent facility cases 2004.9 Ministry of Environment

In the present invention, the sludge of coagulated precipitate generated when food, livestock, and manure waste is chemically treated with a coagulant and then biologically treated with activated sludge has a high water content of 80-90% even after centrifugation and is large, so it is transported and stored. and difficult to dispose of. In addition, disputes between local governments continue due to the ever-shortening waste landfills, and civil complaints due to odors are becoming severe even after incineration. Therefore, it is very urgent to establish measures to treat sludge of coagulated sediment of food, livestock by-products, and livestock manure.

It relates to a method for reducing wastewater sludge generated in a wastewater treatment plant. More specifically, activated sludge from wastewater is floated under pressure, a polymer coagulant (CATION) is added to the concentrated sludge, centrifuged, and sludge is made, which is entrusted to an environmental company. However, the moisture content of the sludge is more than 80%.

In the present reduction invention, a mixing ratio of quicklime (CaO) is added to the resulting sludge cake at a ratio of 1: 0.1 - 0.5 and heated to cause a slaking reaction (Ca(OH)₂), so that the sludge of the flocculated precipitate reacts in a chemical reaction. It relates to a method for reducing wastewater sludge, comprising a first step of dehydration and decomposition of a polymer coagulant by high temperature, and a second step of heating and pulverizing the dehydrated sludge cake into particles. Adding quicklime and calcium chloride (CaCl ₂ ) in the first step has the effect of lowering the moisture content of the sludge cake by accelerating the dehydration of the sediment sludge due to an exothermic reaction. In addition, when calcium chloride is added to the sludge cake in the second step, it is effective in particleization due to an exothermic reaction. It is effective to react by mixing calcium chloride and quicklime at a ratio of 0.1-0.5: 0.5-0.9 in the second step.

The present invention reduces the water content of wastewater sludge by about 50% to 90%, thereby reducing landfill cost as well as reducing landfill cost. Furthermore, granular sludge contains organic matter and inorganic matter, so they complement each other to improve the growth of soil microorganisms. Moreover, it can supply alkaline components mainly composed of minerals to acidified soil. In addition, a sustainable recycling system can be provided by recycling waste sludge.

1 is a particle obtained by heating and pulverizing dehydrated sludge cake.
Figure 2 shows a sludge of waste coagulated sediment.

The present invention relates to a method for reducing wastewater sludge generated in a wastewater treatment plant. More specifically, quicklime (CaO) is added to the flocculated sediment sludge in a hydrated state and heated to cause a slaked lime (Ca(OH) ₂ ) reaction to cause a first step in which the sludge of the flocculated sediment is dehydrated into a cake, and the above dewatered It relates to a method for reducing wastewater sludge comprising a second step of heating and pulverizing the sludge cake to make it into particles. Adding quicklime (CaO) and calcium chloride (CaCl ₂ ) in the first step has the effect of lowering the moisture content of the sludge cake by accelerating the dehydration of the sediment sludge due to an exothermic reaction. In addition, when calcium chloride is added to the sludge cake in the second step, it is effective in particleization due to an exothermic reaction.

<Example 1> Slaughtering waste treatment

Wastewater generated from slaughterhouses consists of blood, chicken hair, chicken residues, and washing water resulting from washing after slaughtering. These slaughtering wastes included total solids (TS (mg/L) of 49,690, volatile solids (VS (mg/L) of 42,420, COD Cr (mg/L) of 85,900, BOD5 (mg/L of 60,120, TN (mg/L) of 3,600 is relatively high.

The sludge of the primary coagulated precipitate is separated by aerobic reaction by adding activated sludge after first reacting sludge with sodium aluminate and polyaluminum chloride and coagulating it with a cationic coagulant. The supernatant is subjected to a secondary reaction with the above coagulant, and the secondary coagulated precipitate is mixed with the primary coagulated precipitate, concentrated, and then centrifuged to obtain a sludge cake.

0.1-0.5 kg of quicklime was mixed with 1 kg of the above sludge cake at a ratio of 1: 0.1-0.5, stirred for 10-30 minutes, and then the total weight and moisture content were measured. The results are shown in Table 3 below.

Moisture content (%) of sludge cake according to the mixing ratio of sludge and quicklime division Experimental Example 1 Experimental Example 2 Experimental Example 3 Experimental Example 4 Experimental Example 5 sludge/quicklime 1:0.1 1:0.2 1:0.3 1:0.4 1:0.5 reaction time 10 minutes 15 minutes 20 minutes 25 minutes 30 minutes Moisture content (%) 55.5 52.6 48 43.8 40.5

From the above results, it was found that the sludge cake had a moisture content of 40.5-65.5% when the mixing ratio of sludge and quicklime was mixed at a ratio of 1: 0.1 - 0.5. Therefore, it can be seen that the moisture content of the original sludge cake is reduced from 81-82% to 40.5-55.5%, reducing the total weight of the sludge by about 50%. Disposal of the reduced sludge cake in this way is economical because it can be easily stored and transported and the landfill site can be reduced. In addition, in the case of sludge generated after wastewater treatment at slaughterhouses (cow, pig, goat, etc.), economic effects can be obtained when treated with quicklime.

In the first step above, quicklime (CaO) and calcium chloride (CaCl ₂ ) were added to the slaughtering waste at a ratio of 5:5, 6:4, 7:3, 8:2, and 9:1, and Experimental Examples 1 to 5 and When the moisture content was measured by reacting and separating in the same way, it was confirmed that there was a difference in the moisture content of the sludge cake as 35-50%.

<Example 2> Powdering of reduced sludge

In the reduced sludge cake (moisture content of 40.5-55.5%) obtained in Example 1, quicklime (CaO) is converted into slaked lime (CaOH)2), making it easy to powder. The slurry of the sludge cake was vigorously stirred at 40-50 ° C. at 30-40 rpm for 30-60 minutes using a device equipped with a heater and a stirrer. Moisture vapor and odor were absorbed by a scrubber to obtain a mixture of sludge and minerals in the form of powder or granules with a water content of 2-3%. The above sludge particles may be used as soil fertilizers or soil improvers. Methyl and sulfa odors generated by sludge quicklime reaction can be safely treated by passing through existing water scrapers, acid-alkaline treatment facilities, or electrostatic precipitators or boiler tubes to collect and reduce these gases.

The moisture content of the sludge cake powdered particles was measured under the same reaction conditions as in Experimental Examples 1 to 5, and is shown in Table 4 below.

Moisture content (%) of reduced sludge powder particles division Experimental Example 1 Experimental Example 2 Experimental Example 3 Experimental Example 4 Experimental Example 5 Sludge Cake Moisture (%) 55.5 52.6 48 43.8 40.5 Powder particle moisture (%) 3.5 3.1 2.8 2.5 2.1

From Table 2 above, it can be seen that the higher the quicklime content in the sludge cake, the lower the moisture content. In the second step above, quicklime (CaO) and calcium chloride (CaCl ₂ ) were added to the sludge cake at a ratio of 5:5, 6:4, 7:3, 8:2, and 9:1 to experiment examples 1 to 5 and When the moisture content was measured by reacting and separating in the same way, it was confirmed that there was a difference in moisture content of 1.5-3% of the slut powder.

When the reduced sludge cake is heated and pulverized into powder, the moisture content is 2-3%, which makes it easy to store and transport and reduce the landfill site. It can also be used as a soil fertilizer or soil improver.

<Example 3> Livestock manure waste treatment

Total solids (TS) of wastes from livestock manure were 46,300 mg/L, volatile solids (V/S) were 32,000 mg/L, COD Cr 60,400 mg/L, BOD5 34,500 mg/L, and TN 3,500 mg/L. relatively high.

Meanwhile, the pig manure slurry had about 8.50% of total solids (TS), 68.94% of volatile solids (VS)/total solids (TS), 13,380 mg/L of BOD, 15,721 mg/L of COD, and 23.636 mg/L of SS. , TP is 1,198 mg/L and TKN is 9,800 mg/L. Odor substances usually generated in pig farms are composed of volatile fatty acids (VFA), phenols, indoles, and nitrogen compounds (Schaefer, 1977; Williams and Evans, 1981).

In the present invention, pig excrement collected from a pig farm was separated, liquid was treated as wastewater, and solid pig excrement was used as a sample. 0.1-0.5 kg of quicklime was mixed at a ratio of 1: 0.1-0.5 with respect to 1 kg of pig manure with a moisture content of 45-50%, and then stirred for 10-30 minutes, and then the total weight and moisture content were measured. The results are shown in Table 5 below.

Moisture content of pork powder cake according to the mixing ratio of pork powder and quicklime (%) division Experimental Example 1 Experimental Example 2 Experimental Example 3 Experimental Example 4 Experimental Example 5 Pork meal/quicklime 1:0.1 1:0.2 1:0.3 1:0.4 1:0.5 reaction time 10 minutes 15 minutes 20 minutes 25 minutes 30 minutes Moisture content (%) 25.5 26 26.5 27 27.5

From the above results, when the mixing ratio of pig manure and quicklime was mixed at a ratio of 1: 0.1 - 0.5, the moisture content of the pig manure cake was 25.5 to 27.5%. Therefore, it can be seen that the moisture content of pork bun cake is reduced from 45 to 50% to 25.5 to 27.5% by heating and reacting with quicklime for 30 minutes.

The pork manure sludge cake reduced to a moisture content of 25-27% was treated in the same manner as in Example 2 to obtain particles in which inorganic substances and sludge were mixed in the form of powder or granules having a moisture content of 2-3%. The above sludge particles can be used as soil fertilizers or soil conditioners.

<Example 4> Food waste treatment

Total solids (TS) 190,000 mg/L, volatile solids (VS) 154,300 mg/L, COD Cr 206,100 mg/L, BOD5 138,300 (mg/L), and TN 3,600 mg/L from food waste. it's high A total of 88% of food waste is generated from households and restaurants, in the order of household 69%, restaurants 19%, group cafeterias 5%, agricultural and fishery markets 4%, large-scale stores 2%, and tourist lodging facilities 1%. Although the composition and content of food waste vary depending on the emission source, its relatively high protein content makes it useful as feed, but its high moisture content poses a risk of growth of pathogenic microorganisms. Production and dry feed are sorted, crushed, heated/dried, sorted, and produced.

In the process of treating food waste in the above, the solid and liquid were separated from the food waste that had undergone screening and crushing, and then the obtained food waste was used as a sample.

0.1-0.5 kg of quicklime was mixed at a ratio of 1: 0.1-0.5 with respect to 1 kg of food waste with a moisture content of 45-50%, and then stirred for 10-30 minutes, and then the total weight and moisture content were measured. The results are shown in Table 6 below.

Moisture content (%) of food cake according to the mixing ratio of food waste and quicklime division Experimental Example 1 Experimental Example 2 Experimental Example 3 Experimental Example 4 Experimental Example 5 sludge/quicklime 1:0.1 1:0.2 1:0.3 1:0.4 1:0.5 reaction time 10 minutes 15 minutes 20 minutes 25 minutes 30 minutes Moisture content (%) 25.5 26 26.5 27 27.5

From the above results, when the mixing ratio of food cake and quicklime was mixed at a ratio of 1: 0.1 - 0.5, the moisture content of the food cake was 25.5 to 27.5%. Therefore, it can be seen that the moisture content of the food cake is reduced from 45 to 50% to 25.5 to 27.5% by heating and reacting with quicklime for 30 minutes.

The food sludge cake reduced to a moisture content of 25-27% was treated in the same manner as in Example 2 to obtain particles in which inorganic substances and sludge were mixed in the form of powder or granules having a moisture content of 2-3%. The above sludge particles can be used as soil fertilizers or soil conditioners.

The present invention reduces the water content of wastewater sludge by about 50% to 90%, thereby reducing the cost of landfilling of the sludge as well as reducing the land for landfilling. Furthermore, since the granulated sludge contains organic matter and inorganic matter, it acts as an antagonist to the water activity and respiration of the soil, improving the growth of soil microorganisms. In addition, a sustainable recycling system can be provided by recycling waste sludge.

Claims (6)

Quicklime (CaO) and calcium chloride are added to the waste sludge obtained by wastewater treatment with coagulant and activated sludge and heated to obtain a sludge cake by adding quicklime (CaO) and calcium chloride to the waste sludge by dehydrating the sludge by slaking reaction, and adding quicklime and calcium chloride to the waste sludge at a ratio of 1:0.4 -0.45: The first step of reacting by adding at a weight ratio of 0.05-0.1, and
A method for reducing waste sludge comprising a second step of heating and pulverizing the dehydrated sludge cake to make it into particles. The method of reducing waste sludge according to claim 1, wherein the waste is selected from livestock, manure, or food. delete delete The waste sludge according to claim 1, wherein the granulation is performed by heating and grinding the dehydrated sludge cake at 40-50 ° C. at 30-40 rpm for 30-60 minutes using a device equipped with a hot air balloon and an agitator. reduction method. delete

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