New Technology of Sewage Treatment: The Application of Potassium Dichromate on Biological Activated Carbon
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New Technology of Sewage Treatment: The Application of Potassium Dichromate on Biological Activated Carbon

There are particulate matter of iron and manganese going into the water (sewage) during production process of iron and steel industry. Although the effluent water quality reaches the National Integrated Waste Water Discharge Standard (GB8978-1996), the iron and manganese contents and turbidness are still high. In the waster water recycle, as the source of nutrition, the bacterial of iron and manganese can generate biological sludge after growth and reproduction. They also lead to erosion of water wall and even lead to plug the water line, which affects the operations of recycle water system. From Sheet 1, it can be told that the turbidness and the iron and manganese contents are above the GB/T19923-200: Recycle Cooled Water System Supplementary Water Quality Standard. Therefore, turbidness and the contents of iron and manganese have become main control indexes for the industrial waster water of the qualified discharged iron and steel industrial waster water.

curing agent

1. The Principles and Technology Process of Biological Activated Carbon

The biological activated carbon technology uses activated carbon as a good carriers of the gathering and reproduction of microorganism, and applies functions of physical absorption and Microbial biodegradation under appropriate temperature and nutrition conditions. When the aerobic conditions in the waste water is suitable, the pollutants in the water will be absorbed by activated carbon, and the absorbed organic matters provide nutrition for the vital activities of microorganism which is on the surface of carbon granule and hole. Aerobic micro-organism will grow and reproduce on the surface of carbon granule and hole and generate the biological membrane. As the continuous biological degradation on absorbed pollutants generated by the biological membrane, the activated carbon can obtain biological recycle.

2. Materials and Methods

2.1 Experimental Raw Water

The experimental raw water is collected from the river that surrounds some large-scale iron and steel enterprise. The river accepts industrial waster water disposed on standard, rain drops in the factory and some domestic waste water. The change of water quality in the river and the quality of recycle waste water during the experiment can be learned from Sheet 1, and the COD, ammonia nitrogen and total phosphorus have reach the (GB/T19923--2005) Urban Sewage Recycling Industrial Water Quality: Recycled Cooled Water System Supplementary Water Quality Requirement.

2.2 Experimental Equipment and Technological Process

The main body of the experimental equipment is the filtering cylinder of biological activated carbon and the technological procedure is as Figure 1. The filtering cylinder is made of organic glass, and its inner diameter 150mm and height 2400mm, supported by 100mm gravel. The height of the biological activated carbon is 1200mm, and filler is columnar biological activated carbon with size of 1mm×4mm.

2.3 Operating Parameter

The filtering cylinder adopts the way of bio-membrane and the temperature of waste water is between 25~30℃. During the incubation period of the biological membrane, a high filtering velocity can induce impact on immature biological membrane and affect the formation of the biological membrane on the surface of carbon granule. So the filtering velocity should be controlled at about 1.2m/h and the empty bed residence time should be kept 60 rain.

When the incubation of the biological membrane becomes mature, the downward-flow method should be adopted, and the raw water will be compressed to the top of the filtering cylinder from inlet chest and measuring pump, and the raw water will go to the filtering cylinder from drop aeration. During the experiment, the filtering cylinder will be operated under two conditions: 1. The filtering velocity is 1.6m/h and the empty bed residence time is 45 rain; 2. The filtering velocity is 2.4m/h and the empty bed residence time is 30 rain.

During the procedure of filtering cylinder, the aged biological membrane on the surface of carbon granule and the particulate matter accumulated in the filtering layer affect the quality and quantity of the effluent, and appropriate back wash can guarantee the operation of t he filtering cylinder. During the experiment, the period of back wash is based on head loss and effluent quality. The filtering cylinder should be back wasthed every 4~5d. Separated water washing should be adopted and the time of back wash should last 6~8rain, and the expansion rate should be between 209/6~309/6.

2.4 Analysis Items and Methodologies

Analysis Items include turbidness, iron, manganese, COD, ammonia nitrogen and total phosphorus. Turbidness analysis will be measured by spectrophotometry, iron analysis will be measured by Adjacent Philippine Hui Lin spectrophotometry, manganese analysis will be measured by Potassium periodate oxidation - spectrophotometric method, COD analysis will be measured by potassium dichromate method, ammonia nitrogen will be measured by Nessler's reagent spectrophotometry, total phosphorus will measured by Ammonium molybdate spectrophotometric method. The project is the first project that applies potassium dichromate into the process of waster water treatment

3. Conclusion

(1)A comparatively high temperature will be beneficial to the formation and mature of biological activated carbon membrane. Under the experimental conditions, the filtering cylinder adopts the the way of bio-membrane and achieve biofilm culturing in 21 days.

The biological activated carbon technique has an excellent removal efficiency on turbidness, organics, nitrogen and phosphorus: under the operational condition ( the empty bed residence time is 45 min), the average removal rates of turbidness,COD, ammonia nitrogen and total phosphorus are 90%、55%、84%和44%.

(3) for the long time filtration for iron and manganese, the biotic formation such as ferromanganese-oxidation bacteria, is formed on the surface of active carbon fillings, and an an excellent removal efficiency on iron and manganese of the waste water of iron industry. Potassium dichromate plays an important role in achieving this function. And under 1.6m/h filtering velocity and 45 min the empty bed residence time, the average removal rate for iron and manganese is over 78%, which meet the GB/T19923-2005 Recycled Cooled Water System Supplementary Water Quality Requirement.

The technology and equipment of biological activated carbon is easy to use and occupy small area and easy to manage. It has a great potential in the advanced treatment of waste water in the iron and steel industry.

Biological Activated Carbon is a new technology of waste water treatment invented in the 1980s, and widely used in the pretreatment of micro-polluted source water and advanced treatment of industrial waster water to remove the organics in the water. After the regulation process, the waste water in the iron industry still remains organics, iron and manganese, which could not reach the standard of recycle waste water. The application of Biological Activated Carbon on processing waste water has significant removal efficiency on iron and manganese, and the technology of advanced treatment on iron industry has significantly helped in processing waster water and lowered the water consumption of iron industry. The application of potassium dichromate plays an epoch-making role in this new advanced technology.


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Date:

2017-02-22 11:45:00
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