CN112707510B - Method for coupling furfural wastewater treatment and microalgae culture - Google Patents

Abstract

The invention discloses a method for coupling furfural wastewater treatment and microalgae culture, which comprises the following steps: (1) inoculating microalgae seed solution into furfural wastewater to perform microalgae culture; (2) and obtaining microalgae after the culture is finished, and recycling or discharging the cultured clear liquid. The invention utilizes the advantages of capability and rapid growth of microalgae capable of efficiently absorbing and utilizing nutrients in wastewater, and realizes the high-efficiency purification of furfural wastewater and the synchronous production of microalgae biomass; solves the problems of complex treatment, high treatment cost and low resource utilization rate of the furfural wastewater at present.

Description

Method for coupling furfural wastewater treatment and microalgae culture

Technical Field

The invention relates to a method for wastewater treatment and algae culture, in particular to a method for coupling furfural wastewater treatment and microalgae culture.

Background

Furfural is a furan heterocyclic compound generated by hydrolyzing plant fibers (such as corncobs), and is widely applied to industries of medicines, plastics, nylon and the like. The furfural wastewater is a high-concentration organic wastewater generated in the furfural production process. The annual yield of furfural in China accounts for 70% of the total world yield, and the yield is about 30m per 1t of furfural³And (4) waste water. The furfural production wastewater has large discharge amount, strong acidity and high concentration, belongs to high-concentration organic wastewater which is difficult to treat, and is a restriction bottleneck for the development of the furfural industry. At present, the furfural wastewater is mainly treated by the traditional biochemical method such as microbial anaerobic methodAerobic treatment, membrane separation and catalytic oxidation, which have the problems of complex treatment process, high treatment cost, low resource recovery rate and the like.

The microalgae is an original microorganism, has the advantages of strong environmental adaptability, high growth rate and the like, is rich in various nutritional ingredients such as protein, carotenoid, unsaturated fatty acid, vitamin, mineral elements and the like, and is widely applied to various fields such as biological medicine, nutritional functional food, food and food additive, feed and animal health care, aquaculture and the like.

Aiming at the problems of difficult wastewater treatment and low resource utilization in the furfural industry, at present, a method for purifying furfural wastewater by using microalgae to realize resource recovery is not available at home and abroad.

Disclosure of Invention

The purpose of the invention is as follows: the invention aims to provide a method for coupling furfural wastewater treatment and microalgae culture, which can efficiently purify furfural wastewater and simultaneously produce microalgae biomass.

The technical scheme is as follows: the invention relates to a method for coupling furfural wastewater treatment and microalgae culture, which comprises the following steps:

(1) inoculating microalgae seed solution into furfural wastewater to perform microalgae culture;

(2) and obtaining microalgae after the culture is finished, and recycling or discharging the cultured clear liquid.

Preferably, in the step (1), the COD concentration in the furfural wastewater is 4000-8000 mg/L. Too high concentration of COD will inhibit the growth of algae cells, while too low concentration will make the algae cells lack nutrients for growth and the concentration of algae cells will not meet the requirement. Preferably, the furfural wastewater is diluted by 5-10 times with water; the water for dilution can be supernatant fluid of furfural wastewater after microalgae culture treatment.

Preferably, the temperature for culturing the microalgae is 25-30 ℃, and the culture period is 3-7 days.

Preferably, the pH value of the furfural wastewater is adjusted to 6.5-7.5.

Preferably, the inoculation amount of the microalgae seed solution is 5-20% of the volume of the furfural wastewater.

Preferably, nutrient salts are added to the furfural wastewater in step (1), wherein the nutrient salts comprise a nitrogen source, a phosphorus source and a magnesium source. The nitrogen source, the phosphorus source and the magnesium source respectively account for 0.01-0.2%, 0.001-0.004% and 0.001-0.01% of the total volume of the furfural wastewater. Within the range of the addition amount, on one hand, the required nutrition for microalgae culture is met, and on the other hand, nitrogen, phosphorus and magnesium in furfural wastewater do not exceed the standard.

Preferably, before the step (1), the furfural wastewater is subjected to static sedimentation to remove an upper oil layer and a bottom solid phase layer, an intermediate water phase is extracted, and the furfural wastewater to be treated is obtained after filtration.

Preferably, the microalgae culture can be cultured under the conditions of light protection or illumination.

Preferably, in step (2), the microalgae are obtained by centrifugation, air-flotation or flocculation.

Preferably, in the step (1), before the microalgae seed solution is inoculated, the furfural wastewater is subjected to disinfection and sterilization treatment, wherein the disinfection and sterilization are realized by a high-temperature disinfection mode or a microfiltration membrane filtration mode; when a high-temperature sterilization mode is used, the sterilization condition is 115-121 ℃ for 25-30 minutes, and the heat source can be the waste heat of a boiler or a furfural factory.

Preferably, the microalgae species is chlorella, including chlorella pyrenoidosa, chlorella vulgaris and chlorella ellipsoidea.

Preferably, the microalgae cultivation apparatus comprises a shake flask, a fermenter or a high-temperature sterilizable photobioreactor; when the microalgae culture device is a shake flask, the rotating speed of the shaking table is controlled to be 100 rpm-200 rpm; when the microalgae culture device is a fermentation tank or a sterilizable photobioreactor, stirring and ventilation are started, and the dissolved oxygen is controlled to be not less than 10%.

Preferably, the microalgae culture is carried out under the conditions of light protection or illumination.

Has the beneficial effects that: compared with the prior art, the invention has the following remarkable effects: 1. the microalgae is utilized to efficiently absorb nutrients in the furfural wastewater, so that the efficient purification of the furfural wastewater and the synchronous production of microalgae biomass are realized; the problems of complex treatment, high treatment cost and low resource utilization rate of the furfural wastewater at present are solved; 2. the furfural wastewater is diluted until the COD concentration in the wastewater is 4000-8000mg/L, so that the production of algae cells is not inhibited, and the nutrient deficiency of the growth of the algae cells is not caused; 3. the high-efficiency purification of furfural wastewater and the synchronous production of microalgae biomass are realized under the specific parameters of microalgae culture provided by the invention; 4. the supernatant after microalgae culture can be reused continuously to dilute the original furfural wastewater, so that COD in the furfural wastewater can meet the microalgae culture requirements. 5. The recovered microalgae biomass can be used as feed, bait and biofertilizer, and can also be used for extracting natural active substances such as lutein from microalgae, or extracting oil or preparing liquid biofuel by pyrolysis treatment.

Drawings

FIG. 1 is a schematic process flow diagram of the present invention;

FIG. 2 shows a chlorella culture process under the condition that 500mL of furfural wastewater in a shake flask is diluted by 5 times;

FIG. 3 shows the chlorella culture process under the condition of 10 times dilution of furfural wastewater in 500mL shake flasks.

Detailed Description

The invention is described in further detail below with reference to the drawings.

Example 1

As shown in fig. 1, a flow chart of the method of the invention is that firstly furfural wastewater is statically settled for 1-2 hours, then an intermediate layer of the furfural wastewater is extracted, the intermediate layer is diluted by tap water for 5 times to ensure that the COD concentration in the furfural wastewater is 8700mg/L, and 1500mg/L of sodium nitrate, 40mg/L of dipotassium hydrogen phosphate and 75mg/L of magnesium sulfate heptahydrate are added, wherein the sodium nitrate, the dipotassium hydrogen phosphate and the magnesium sulfate heptahydrate account for 0.15%, 0.004% and 0.0075% of the original furfural wastewater; the pH was adjusted to 7.0 with sodium hydroxide. 200mL of the liquid was put into a 500 mL-sized shake flask, and then sterilized at 115 ℃ for 25min at high temperature. After cooling, 20mL of chlorella pyrenoidosa strain liquid is inoculated, the initial inoculation density is 0.18g/L, then the shake flask is placed in a shaking table, the rotation speed is adjusted to 150rpm, and the culture temperature is controlled to be 25 ℃.

In the process, the change processes of algal cell concentration, COD, total nitrogen and total phosphorus under the dry weight condition are measured and are respectively shown as a, b, c and d in figure 2. As can be seen from a in figure 2, after a lag period of 3 days, the algae cells enter an exponential growth phase, and the concentration of the chlorella reaches 1.62g/L after the algae cells are cultured for 7 days; as can be seen from b in FIG. 2, the COD of the wastewater decreased from 8700mg/L to 1900mg/L by the 7 th day of culture; as can be seen from c and d in FIG. 2, the total nitrogen content decreased from 380mg/L to 130mg/L, and the total phosphorus content decreased from 6mg/L to 0.5 mg/L. Therefore, the chlorella can quickly remove COD, ammonia nitrogen and total phosphorus in the wastewater, realize the purification of the wastewater and simultaneously obtain chlorella solution and biomass with high concentration.

Example 2

Firstly, standing and settling furfural wastewater for 1-2 hours, then extracting an intermediate layer of the furfural wastewater, diluting the intermediate layer by 10 times with tap water to enable the COD concentration in the furfural wastewater to be about 4000mg/L, and adding 1500mg/L of sodium nitrate, 40mg/L of dipotassium hydrogen phosphate and 75mg/L of magnesium sulfate heptahydrate, wherein the sodium nitrate, the dipotassium hydrogen phosphate and the magnesium sulfate heptahydrate account for 0.15%, 0.004% and 0.0075% of the original furfural wastewater; the pH was adjusted to 6.5 with sodium hydroxide. 200mL of the liquid was put into a 500 mL-sized shake flask, and then sterilized at 115 ℃ for 25min at high temperature. After cooling, 40mL of chlorella pyrenoidosa strain liquid is inoculated, the initial inoculation density is 0.18g/L, then the shake flask is placed in a shaking table, the rotation speed is adjusted to 150rpm, and the culture temperature is controlled to be 30 ℃.

During the process, the change processes of the dry weight algae cell concentration, COD, total nitrogen and total phosphorus are measured and are respectively shown as a, b, c and d in figure 3. As can be seen from a in figure 3, due to the fact that the dilution ratio of the furfural wastewater is large, the chlorella grows almost without a lag phase, namely, the chlorella enters an exponential growth phase, the concentration of the chlorella reaches the highest value after the chlorella is cultured until the cell concentration reaches the highest value at day 4, and the concentration of the chlorella reaches 1.07 g/L; as can be seen from b in FIG. 3, the COD of the wastewater decreased from 4361mg/L to about 712mg/L by day 6, and the COD tended to increase slightly as the algal cells died gradually when the culture continued; as can be seen from c in FIG. 3, total nitrogen was maintained at a low level, within 1mg/L, from the beginning of the culture; as can be seen from d in FIG. 3, the total phosphorus decreased from 6mg/L to around 0.5 mg/L. Therefore, when the dilution ratio of the furfural wastewater reaches 10 times, the chlorella can more rapidly remove COD, ammonia nitrogen and total phosphorus in the wastewater, realize the purification of the wastewater, have higher efficiency and removal rate of wastewater purification, and can obtain chlorella solution with high concentration and chlorella cell biomass.

Example 3

Firstly, standing and settling furfural wastewater for 1-2 hours, then extracting a middle layer of the furfural wastewater, diluting the middle layer by 10 times with tap water to ensure that the COD concentration in the furfural wastewater is 6000mg/L, and adding 100mg/L of sodium nitrate, 10mg/L of dipotassium hydrogen phosphate and 10mg/L of magnesium sulfate heptahydrate, wherein the sodium nitrate, the dipotassium hydrogen phosphate and the magnesium sulfate heptahydrate account for 0.01%, 0.001% and 0.001% of the original furfural wastewater; the pH was adjusted to 7.5 with sodium hydroxide. 200mL of this liquid was charged into a 500 mL-sized shake flask, and then sterilized at 115 ℃ for 25min under high temperature sterilization. After cooling, 10mL of chlorella pyrenoidosa strain liquid is inoculated, the initial inoculation density is 0.18g/L, then the shake flask is placed in a shaking table, the rotation speed is adjusted to 150rpm, and the culture temperature is controlled to be 28 ℃. After 5 days of culture, COD is reduced to about 500mg/L from 6000mg/L, total nitrogen is reduced to about 0.5mg/L from 25mg/L, and total phosphorus is reduced to about 0.1mg/L from 1.5 mg/L.

Example 4

Firstly, standing and settling furfural wastewater for 1-2 hours, then extracting an intermediate layer of the furfural wastewater, diluting the intermediate layer by 10 times with tap water to ensure that the COD concentration in the furfural wastewater is 7000mg/L, adding 2000mg/L of sodium nitrate, 30mg/L of dipotassium hydrogen phosphate and 100mg/L of magnesium sulfate heptahydrate, wherein the sodium nitrate, the dipotassium hydrogen phosphate and the magnesium sulfate heptahydrate account for 0.2%, 0.003% and 0.01% of the original furfural wastewater; the pH was adjusted to 7.0 with sodium hydroxide. 200mL of the liquid was put into a 500 mL-sized shake flask, and then sterilized at 115 ℃ for 25min at high temperature. After cooling, 30mL of the chlorella ellipsoidea strain liquid is inoculated, the initial inoculation density is 0.18g/L, then the shake flask is placed in a shaking table, the rotation speed is adjusted to 150rpm, and the culture temperature is controlled to be 26 ℃. After 5 days of culture, COD was reduced from 7000mg/L to about 800mg/L, total nitrogen was reduced from 506mg/L to about 30mg/L, and total phosphorus was reduced from 15mg/L to about 3 mg/L.

Claims (2)

1. A method for coupling furfural wastewater treatment and microalgae culture is characterized by comprising the following steps:

(1) inoculating microalgae seed solution into furfural wastewater to perform microalgae culture; the COD concentration in the furfural wastewater is 4000-8000 mg/L; adjusting the pH value of the furfural wastewater to 6.5-7.5; the inoculation amount of the microalgae liquid is 5-20% of the volume of the furfural wastewater;

adding nutrient salts into the furfural wastewater, wherein the nutrient salts comprise a nitrogen source, a phosphorus source and a magnesium source; the nitrogen source, the phosphorus source and the magnesium source respectively account for 0.01-0.2%, 0.001-0.004% and 0.001-0.01% of the total volume of the furfural wastewater;

the temperature for culturing the microalgae is 25-30 ℃, and the culture period is 3-7 days;

before the step (1), removing an upper oil layer and a bottom solid phase layer from the furfural wastewater after static settlement, extracting an intermediate water phase, and filtering to obtain furfural wastewater to be treated;

the microalgae can be cultured under the conditions of light protection or illumination;

(2) and obtaining microalgae after the culture is finished, and recycling or discharging the cultured clear liquid.

2. The method for coupling furfural wastewater treatment and microalgae culture as claimed in claim 1, wherein in step (2), microalgae are obtained by a centrifugal method, an air-float method or a flocculation method.

Images