Treatment results of starch wastewater by different kinds of flocculants
The effect of culture condition on different types of bioflocculant production and its application on actual wastewater treatment were studied in this chapter. The advantages of mixed strain HXJ-1 were as follows: directly using acidic wine wastewater, adapting to wastewater at high concentrations and the presence of less nitrogen. HXJ-1 achieved good flocculating rate when the chemical oxygen demand (COD) was 12,000 mg/L, C/N 20:1. Three kinds of bioflocculants had some good treatment results on starch wastewater, printing and dyeing wastewater and landfill leachate. The treatment effect of XJBF-1 (produced by mixed strain HXJ-1) on the starch wastewater was better than that of traditional polyacrylamide and other bioflocculants produced by a single bacterial (X15BF-1) and yeast strain (J1BF-1). XJBF-1 had better treatment results on three types of wastewater. It also had good removal rate of chromaticity, especially on the starch wastewater , the printing and dyeing wastewater; the removal rate was up to 88%, and the starch wastewater COD removal rate was up to 86%.
- Alcoholic wastewater
- mixed strains
- culture condition
- actual wastewater treatment
Microbial flocculent, the secondary metabolites with flocculating activity and produced by microorganisms , is a new water treatment agent with efficient, safe, natural degradation characteristic to flocculate and sediment the solid suspended particles and colloidal particles which are not easily degradable in water [2, 3]. Most bioflocculants are still in the developmental stage and under research because of the high cost of the culture medium and the lack of high production of flocculating engineering fungus. Therefore, the synthesis of microbial flocculants from inexpensive carbon source showed its potential benefit since it could address the critical problems of substrate costs . The use of industrial wastewater, such as soy sauce wastewater, and biological hydrogen production waste as an alternative medium to reduce the cost of production of microbial flocculants has been reported in recent years [5, 6]. China is one of the largest alcoholic beverage-producing and -consuming countries; nutrients in the alcoholic wastewater might be used as free resources for microorganism growth and synthesis of bioflocculants to reduce the cost of culture medium, and the pollutant in the wastewater might also be reduced after it is utilized by microorganisms. Therefore, the idea ‘use waste to treat waste’ may realize material recycling and will benefit the environment and society. In addition,
Only a few references on actual wastewater treatment by bioflocculant could be found at present . In order to put bioflocculant into use on actual wastewater treatment, based on previous study [9, 10], different culture conditions on single strains and mixed strains were studied in this chapter. Three kinds of bioflocculants produced by different strains were used in actual wastewater treatment. These results will provide reference for complex bioflocculant research and future applications.
2. Materials and Methods
The flocculant-producing strains used in the experiments were isolated and selected from activated sludge from Chengdu wastewater treatment plant. They were primarily identified to be
2.1.2. Wastewater quality parameters
Wastewater came from Chengdu alcoholic production plant. The water quality parameters are reducing sugar 20.80 g/L, chemical oxygen demand (COD) concentration of 90,000 mg/L and PH3.6.
2.1.3. Wastewater fermentation medium
Appropriate dilution of alcoholic wastewater and pH adjustment according to the testing requirements, adding nitrogen (urea as the nitrogen source) according to a certain C/N ratio, and sterilization at 121℃ after 30 min were performed.
2.1.4. Actual wastewater for treatment
The landfill leachate: from Chengdu landfill plant. The water quality parameters: COD concentration: 1944 mg/L, turbidity: 1440 degrees, chromaticity: 512 times, SS: 11.04 g/L and pH: 6.5.
The starch wastewater: from Chengdu medicine production plant. The water quality parameters: COD concentration: 9660 mg/L, turbidity: 2098 degrees, chromaticity: 320 times, SS: 1.094g/L and pH: 2.3.
The printing and dyeing wastewater: from Chengdu textile plant. The water quality parameters: COD concentration: 760 mg/L, turbidity: 165 degrees, chromaticity: 1200 times, SS: 0.348g/L and pH: 8.7.
2.2.1. Measurement of flocculating activity
The flocculating activity was measured using the previous method  with a slight modification . Ninety-three mL Kaolin suspension (1g/L), 5 mL of 1% CaCl2 solution and 2 mL of bioflocculant were taken in a 200 mL beaker, and the pH was adjusted to 7.0. Then the beaker was placed in an electric mixer for 250 r/min of fast stirring for 1 min, 60 r/min of slow stirring for 2 min and then kept unstirred for 15 min at room temperature. The supernatant was carefully transferred to a utensil, and the optical density of the supernatant (OD550) was measured by spectrophotometer, keeping an equal volume of distilled water as a control. The flocculating rate (FR) indicates the flocculating activity, which is calculated as follows:
where A is the absorbance at 550 nm of control and B is the absorbance at 550 nm of treatment.
2.2.2. The effects of culture conditions on microbial flocculant production and flocculating activity
Ten percent relative inoculum size (V/V cell concentration: 108/L)
2.2.3. Different bioflocculants applications on actual wastewater treatment
After 93 mL starch wastewater, printing and dyeing wastewater and landfill leachate were poured into three 200 mL beakers respectively, 5 mL of 1% CaCl2 solution and 2 mL of four different types of flocculants were added in each of the 200 mL beaker, and the pH was adjusted to 7.0. Then the beaker was placed in an electric mixer for 250 r/min of fast stirring for 1 min and 60 r/min of slow stirring for 2 min and then kept unstirred for 15 min at room temperature. Variations in wastewater COD, turbidity, chromaticity and SS were measured before and after the treatment. The COD speed-measuring device was used to measure COD , the spectrophotometric method was used to measure turbidity , the dilution factor method was used to measure chromaticity  and the constant weight method was used to measure SS .
3. Results and discussion
3.1. The effect of wastewater concentration on bioflocculant production
The wastewater concentration of the fermentation liquid with the effect of different microbial flocculant production is shown in Figure 1.
3.2. The effect of C/N on bioflocculant production
The effect of C/N in the fermentation broth on bioflocculant production by different strains is shown in Figure 2. It could also be seen that the flocculating rate of HXJ-1 increased rapidly with the increasing C/N ratio and achieved the maximum rate 89.3% at C/N 20:1 and then declined slightly.
3.3. The effect of initial medium pH on bioflocculant production
The effect of initial pH of alcoholic wastewater fermentation medium on bioflocculant production by different strains is shown in Figure 3. The flocculating rate of
3.4. Treatment effect of different flocculants on the starch wastewater
The starch wastewater normally has a high COD concentration and turbidity. Its main component of starch wastewater is starch, protein and carbohydrate. The results of starch wastewater treatment of four different bioflocculants are shown in Table 1. The COD removal rate was very high, reaching 81% and 86% by X15BF (produced by bacterial strains) and XJBF-1 (produced by mixed strains of bacteria and yeast) respectively, much higher than that of polyacrylamide (PAM) removal rate of COD. At the same time, the removal rate of SS in the starch wastewater and three kinds of microbial flocculants was equal to PAM but was quite superior to turbidity and chromaticity removal in the starch wastewater compared with PAM. The results also showed that the removal rates of all indicators in the starch wastewater by XJBF-1 were the highest, and excellent wastewater treatment results were achieved compared with the traditional flocculant and other two kinds of bioflocculants in starch wastewater treatment.
3.5. Treatment effect of different flocculants on landfill leachate
The composition of landfill leachate is very complex, with variations in water quality and quantity and a high concentration of organic matter. The landfill leachate treatment results of four kinds of flocculants are shown in Table 2, which indicated that the removal rates of turbidly, chromaticity and SS by three bioflocculants were not as high as PAM, especially the X15BF and J1BF produced by a single bacterial and yeast strain. However, the COD removal rate reached 73% by XJBF-1 (produced by mixed strains), while the PAM COD removal rate was only 58%. Although the removal rates of turbidity, chromaticity and SS of landfill leachate by XJBF-1 were not as good as PAM, the treatment effect had significantly improved compared with the bioflocculants produced by a single strain. The removal rates of chromaticity and SS have been more than 70%, except for the turbidity removal rate which is only 50%. It is difficult to treat landfill leachate because of its complex composition. Therefore, relatively speaking, these types of bioflocculants played a certain role in landfill leachate treatment, especially XJBF-1 produced by mixed bacteria and yeast showed good results on landfill leachate treatment.
3.6. Treatment effect of different flocculants on the printing and dyeing wastewater
The printing and dyeing wastewater has a high chromaticity degree and complex composition; the wastewater has greater biological toxicity, which contains dyes, sizing additives, oils, acids, alkalis, fibre impurities and inorganic salts, the structure of dyes, nitro and amino compounds, copper, chromium, zinc, arsenic and other heavy metals. The treatment effects by four kinds of bioflocculants on the printing and dyeing wastewater are shown in Table 3. From the experimental results, COD removal rates on the printing and dyeing wastewater by four flocculants were low, only 45–57%, but there was a high removal rate of suspended particles. The turbidity and chromaticity removal rates by X15BF (produced by a single bacterial strain) and XJBF-1 (produced by mixed bacterial and yeast strains) achieved 70–80%. The results were far better than those of J1BF produced by yeast and traditional PAM. Especially in XJBF-1, the chromaticity removal rate was high as 88%, much higher than those of PAM and the other two microbial flocculants produced by bacteria and yeasts respectively. The SS removal efficiency by PAM was slightly better than that of the three types of microbial flocculants.
The advantages of mixed strain HXJ-1 were as follows: directly using acidic wine wastewater, adapting to wastewater at high concentrations and the presence of less nitrogen. Three kinds of bioflocculants had some good treatment results on the starch wastewater, printing and dyeing wastewater and landfill leachate, respectively. The treatment effect of XJBF-1 (produced by mixed strains) on the starch wastewater was better than that of traditional PAM, and XJBF-1 had better treatment results on the three types of wastewater than those of X15BF-1 and J1BF-1 produced by single bacterial and yeast strain respectively. XJBF-1 had good removal rates for three kinds of wastewater chromaticity, especially for the starch wastewater and dyeing wastewater.
This study was supported by the Sichuan basic application project (Fund No. 05JY029-026-2). The authors are grateful to Dr. Chi Chang (Agriculture and Agri-Food, Canada), Prof. Yang Jinxia (Sichuan University, China), Mr. Zhang jing (General Manager of Chengdu Hen Shi English Translation Company) and Ms Song Jinling for discussion and English editing.
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