TWI491567B - Biological treatment of wastewater - Google Patents

Description

Wastewater biological treatment

The invention relates to a wastewater treatment method, in particular to a biological treatment method for wastewater.

Bioflocculant is a metabolite produced by microorganisms themselves or microorganisms. The main components are cellulose, protein, glycoprotein, polysaccharide and deoxyribonucleic acid. They have high charge or hydrophilicity on the surface and can flocculate and precipitate. Suspended particles, bacterial cells and colloidal particles in water, in particular, bioflocculants have high efficiency, safety, non-toxicity, environmental protection, biodegradability, wide application range and low dosage compared with other commonly used flocculants. And the price is low and so on.

In addition, from the current research on the application of bioflocculants at home and abroad, bioflocculants can be excellent for BOD, TOC, CN, COD, suspended matter, heavy metals, turbidity, color and oil in wastewater. The stable removal effect can be applied to the flocculation and sedimentation treatment of livestock wastewater, petrochemical wastewater, dyeing and finishing wastewater, food processing wastewater, emulsifying wastewater, drinking water drinking water, etc., as well as improving the performance of activated sludge.

However, in the preparation of bioflocculants, flocculating strains must be screened first, usually in a solid medium for primary screening, followed by re-screening with fermentation medium, and then the flocculation effect is checked with a kaolin suspension, which clearly shows the workload of this screening method. Large and inefficient, and the cost of culture is considerable after screening flocculating strains. Therefore, for the mass production of bioflocculants, low productivity and high production cost are urgent problems to be solved, otherwise they will be Limitations are imposed on wastewater treatment applications.

Therefore, the object of the present invention is to provide a biological treatment method for wastewater which can rapidly and efficiently produce a bioflocculant at a low yield and obtain a good flocculation and sedimentation effect of the wastewater.

Therefore, the biological treatment method for wastewater of the present invention comprises: (a) obtaining an activated sludge from a wastewater treatment system; and (b) applying the activated sludge to a surface of a solid medium to purify and separate the activated sludge. (c) selecting a flocculating cell from the solid medium, the surface of the flocculating cell having a jelly; (d) inoculating the flocculating cell into a liquid medium to culture a first bioflocculant; and (e) placing the first bioflocculant into the wastewater treatment system for flocculation precipitation treatment.

The effect of the invention is that, after obtaining the activated sludge from the wastewater treatment system, the flocculating activity can be quickly screened by directly observing whether the surface of the bacterial cell separated from the activated sludge forms a gel on the solid medium. The bacterial cells are cultured to obtain a bioflocculant with good flocculation activity, stability, high yield and low cost, and can be used for flocculation and sedimentation of the wastewater of the wastewater treatment system, thereby achieving good treatment results, and Reduce processing costs.

The biological treatment method for wastewater of the present invention comprises steps (a) to (h) in sequence:

In step (a), an activated sludge is obtained from a wastewater treatment system as a source of flocculated cells. Here, the wastewater treatment system refers to Hong Yuanxing The wastewater field of the company, which is an activated sludge tank (aeration tank) taken from one of the activated sludge units of the wastewater treatment system.

In step (b), a small amount of activated sludge is taken using an inoculating loop, and the activated sludge is applied to the surface of a solid medium (flat dish) by scribing to purify and separate the cells in the activated sludge. .

The solid medium used was 12 g of amica, 5 g of beef extract, 10 g of glucose, 2 g of potassium dihydrogen phosphate (KH ₂ PO ₄ ), and 5 g of dipotassium hydrogen phosphate (K ₂ HPO ₄ ).

In the step (c), after the activated sludge collected is purified and cultured, the morphology of the surface of the solid medium is directly observed by an optical microscope, and the cells having a gel on the surface are screened to serve as flocculating cells.

The gel on the surface of the cells is a metabolite excreted by the cells during the growth process. The main components are cellulose, protein, glycoprotein, polysaccharide and deoxyribonucleic acid. Further, the flocculating fungus is a fungus (such as a yeast), a bacterium, or a combination thereof.

In the step (d), the selected flocculating cells are adhered with a bacterium stick and inoculated into a triangular flask containing 15 ml of liquid medium, and cultured at a temperature of 35 ° C for 3 to 4 days. A first bioflocculant having a volume of 15 ml and a bacterial concentration of 800 ml/g can be cultured.

Wherein, the liquid medium comprises 5 g of beef extract, 10 g of glucose, 2 g of potassium dihydrogen phosphate (KH ₂ PO ₄ ), and 5 g of dipotassium hydrogen phosphate (K ₂ HPO ₄ ), and the initial pH value thereof 7.

In the step (e), the cultured first bioflocculant is placed in the discharge water of the mixed gelation tank of the wastewater treatment system (alloyed aluminum sulfate has been used) In the coagulation treatment, the flocculation precipitation treatment is carried out.

In the step (f), the first bioflocculant is mixed with the discharged water of the biological sedimentation tank (the final settling tank) of the activated sludge unit, and the mixed volume ratio of the two is between 0.01 and 0.02. After 3 to 4 days of cultivation, a second bioflocculant was prepared, which had a volume of 5 liters and a flocculating cell concentration of between 300 and 380 mg/l.

The discharged water of the biological sedimentation tank has a COD value of between 220 and 280 mg/l, and will continue to be introduced into the mixed gelation tank afterwards, and the precipitate is removed by adding aluminum sulfate as a coagulant. Colloidal particles and suspended particles.

In the step (g), taking the discharge water (about 8 to 9 tons) of the second bioflocculant and the biological sedimentation tank (the final sedimentation tank) so that the volume ratio is between 0.01 and 0.02. Mixing in a large culture tank of the wastewater treatment system, and adding glucose (or molasses), urea and phosphorus to the large culture tank, wherein the amount of glucose is between 10 and 20 kg, and the amount of urea is 50 g. And the amount of phosphorus is less than 1g, and simultaneously aeration, to ensure that the dissolved oxygen value of the culture system is greater than 2mg / l, after 3 to 4 days of cultivation, to obtain a third bioflocculant, the weight of which is 10 metric tons, the concentration of flocculating bacteria contained is between 300 and 380 mg/l.

In the step (h), the cultured third bioflocculant is placed in the outflow water of the mixed gel pool to be subjected to flocculation precipitation treatment.

The invention is further illustrated by the following examples, but it should be understood that this embodiment is intended to be illustrative only and not to be construed as limiting.

<Screening results of flocculated cells>

By using the scribing separation method and the observation of the optical microscope, four flocculated cells with gelatinous surface were screened from the activated sludge in the wastewater field of Hongyuan Industrial Co., Ltd., and the first was detected by spectrophotometer. The absorption value of the bioflocculant at a wavelength of 505 nm (Mycelial cells), 560 nm (test yeast), and 600 nm (bacterial bacteria) showed that the highest absorption value at a wavelength of 505 nm was at a wavelength of 560 nm and 600 nm. The absorption value is relatively low, and it can be seen that the selected flocculating cells are mycelia, yeast and bacteria, and the mycelium concentration is the highest.

<Effect of culture days on the synthesis of the first bioflocculant>

The outflow water of the mixed gel condensate tank of the waste water field of Hongyuan Industrial Co., Ltd. was collected, which has been coagulated by aluminum sulfate and filled into 100 ml in 6 beakers (No. 1~6 respectively). The outflow water of the mixed gel pool.

Next, 1 ml of the negative coagulant was added to the beaker of No. 2, and another 1 ml of the flocculating liquid solution which was cultured for 0 days, 3 days, 4 days, and 5 days in the triangular flask was added to the No. 3 to 6 beakers.

Then, after a flocculation test for 10 minutes, the COD value of the supernatant liquid in the beakers Nos. 1 to 6 was measured, and the results are shown in [Table 1].

It can be seen from the results of [Table 1] that the flocculated bacterial liquid (see No. 4, 5) after the culture for 3 days and 4 days, that is, the first bioflocculant, has a better flocculation effect on the outflow water of the mixed gelation pool. And in the flocculation test for about 2 minutes, the rubber feathers have been rapidly formed in the beaker. It is speculated that the physiological condition of the flocculated cells is logarithmic growth phase and stable phase, and the metabolites produced by them have negatively charged ions. The electro-neutralization method collects the positively charged colloidal particles on the surface after coagulation to form larger particles and then sediments and removes. Therefore, the culture days of the bioflocculant prepared by the invention are limited to between 3 and 4 days. Although the flocculation effect is not superior to the use of negative coagulant (see No. 2), it is clear that the COD value of the discharged water can meet the discharge standard, which proves that the bioflocculant prepared by the present invention replaces the negative coagulation aid. The feasibility of using the agent.

<Flocculation effect of the third bioflocculant>

The outflow water of the mixed gel pool of the wastewater field of Hongyuan Industrial Co., Ltd. will continue to be introduced into a floating tank for treatment.

The third bioflocculant is obtained by the step (f) and the step (g) of the first bioflocculant obtained by the step (d), and is used for completely replacing the negative coagulant (slow mixing). And directly added to the above-mentioned floating tank, the flocculation effect produced is shown in [Table 2], and it is understood that the bioflocculant prepared by the present invention has good COD and SS in the water body in the field operation of the wastewater field. Precipitation removal effect.

Therefore, the present invention separates the cells from the activated sludge taken from the wastewater treatment system, and directly observes the morphology of the cells by an optical microscope, thereby rapidly screening the cells forming a gel on the surface to serve as flocculating cells. After 3 to 4 days of culture, a bioflocculant with good flocculation activity and stability can be obtained, so that high yield and low cost can be achieved.

Moreover, in the dyeing and finishing wastewater treatment process, the prepared bioflocculant is directly placed into the slow mixing stage of the wastewater treatment system, and it is apparent that it can completely or partially replace the slow mixing stage of the wastewater treatment system. The negative coagulant, in this way, not only allows the discharge water quality of the wastewater treatment system to meet emission standards, but also effectively reduces wastewater treatment costs.

The above is only the preferred embodiment of the present invention, and the scope of the invention is not limited thereto, that is, the simple equivalent changes and modifications made by the scope of the invention and the description of the invention are All remain within the scope of the invention patent.

Claims (10)

A biological treatment method for wastewater comprises: (a) obtaining an activated sludge from a wastewater treatment system; (b) applying the activated sludge to a surface of a solid medium to purify and separate the bacteria in the activated sludge (c) selecting a flocculating cell from the solid medium, the surface of the flocculating cell having a jelly; (d) inoculating the flocculating cell into a liquid medium to culture the first bioflocculation And (e) placing the first bioflocculant into the wastewater treatment system for flocculation precipitation treatment. The biological treatment method for wastewater according to claim 1, wherein in step (b), the activated sludge is applied to the surface of the solid medium by using a scribing method, the solid medium containing agar and beef Extract, glucose, potassium dihydrogen phosphate, and dipotassium hydrogen phosphate. The biological treatment method for wastewater according to claim 1, wherein in step (c), the flocculated cells are screened through observation by a microscope. The biological treatment method for wastewater according to claim 1, wherein in the step (c), the flocculating fungus is a fungus, a bacterium, or a combination thereof. The wastewater biological treatment method according to any one of claims 1 to 4, wherein, in the step (d), the initial pH value of the liquid medium is 7, the culture temperature is 35 ° C, and the culture time is Between 3 and 4 days. The wastewater biological treatment method according to claim 5, wherein in the step (d), the liquid medium comprises beef extract, glucose, potassium dihydrogen phosphate, and dipotassium hydrogen phosphate. The biological treatment method for wastewater according to claim 5, further comprising a step (f), the first bioflocculant obtained by the step (d), and the activated sludge unit of the wastewater treatment system The mixed water is mixed to obtain a second bioflocculant, and the mixed volume ratio of the first bioflocculant to the discharged water of the activated sludge unit is between 0.01 and 0.02, and the cultivation days are between 3 ~4 days between. According to the wastewater biological treatment method described in claim 7, further comprising a step (g), the second bioflocculant obtained by the step (f) is mixed with the discharged water of the activated sludge unit, and Adding glucose, urea and phosphorus, and simultaneously aerating to obtain a third bioflocculant, the mixing volume ratio of the second bioflocculant to the discharged water of the activated sludge unit is between 0.01 and 0.02 The number of days of cultivation is between 3 and 4 days. According to the biological treatment method for wastewater according to claim 8, the method further comprises a step (h) of continuously depositing the third bioflocculant into the wastewater treatment system for flocculation precipitation treatment. According to the biological treatment method for wastewater according to claim 8, wherein in step (g), the amount of water discharged from the activated sludge unit is between 8 and 9 metric tons, and the amount of glucose used is between 10 and 10 ~20 kg, the amount of urea used is 50 grams, the amount of phosphorus used is less than 1 gram, and the dissolved oxygen value of the culture system is controlled to be 2 mg / liter.