Method for repairing arsenic-containing wastewater by using sludge

[0024] Example 1:

[0025] The method of using sludge to repair arsenic-containing wastewater involved in this embodiment specifically includes the following steps:

[0026] (2) Pre-cultivation of sludge

[0027] Select 200-500 parts of urban sewage plant sludge, industrial organic sludge or anaerobic digestion sludge according to parts by weight, add 70 parts by weight of ferrous sulfate and 40 parts of potassium nitrate, then put them in the incubator, stir and mix, and fill with nitrogen 20 -60 minutes, control the temperature at 20-30°C and leave it for 7-10 days to prepare pre-cultured sludge for use;

[0028] (2) Preparation of NAFO medium

[0029] Add the medium to the bioreactor according to the following weight ratio: NH 4 Cl 25-30 parts, K 2 HPO 4 20-30 parts, MgSO 4 10-15 parts, CaCl 2 1-3 parts, 80-410 parts of anhydrous sodium acetate, 80-170 parts of sodium nitrate or 100-210 parts of potassium nitrate, FeCl 2 ·4H 2 O200-400 parts or heptahydrate FeSO 4 270-560 parts or 85-180 parts of iron sulfide and 100-1000 parts of water; mix to obtain NAFO medium;

[0030] (3) Preparation of biological iron flocculant

[0031] The pre-cultured sludge prepared in step (1) was inoculated into the NAFO medium prepared in step (2) at a volume ratio of 5-30%, adjusted to a pH value of 6.5-7.8, and then transferred to the bioreactor with 1 Fill with nitrogen at a rate of -25 mL/min for 30-60 minutes, control the temperature at 20-30°C and seal for 5-25 days. After 5-25 days, the sludge turns from black to yellow-brown, which is the bio-iron flocculant formed on the inner wall of the bioreactor ;

[0032] (4) Removal of arsenic from wastewater

[0033] After standing the bioreactor for 1-5 hours for precipitation, the bio-iron flocculant prepared in step (3) is centrifuged at 6000 rpm for 5-15 minutes, and the supernatant is filtered off, and then the arsenic content tested to be purified The wastewater is charged into the bioreactor, so that the ratio of the bio-iron flocculant to arsenic in the bioreactor is 0.06-0.48g bio-iron flocculant: 1mg arsenic, adjust the stirring rate of the bioreactor to 80-120rpm/min, control The temperature of the bioreactor is 20-30°C, and after 2-8 hours of stirring, the arsenic in the wastewater can be removed to achieve purification.

[0034] The step (4) removing arsenic from wastewater in this embodiment can be replaced by the following steps:

[0035] Centrifuge the liquid in the bioreactor in step (3) to remove the supernatant, take out the bio-iron flocculant and add it to the arsenic-containing wastewater, or prevent the bio-iron flocculant in the freeze dryer at -55 to -65°C Freeze and dry for 20-36 hours to prepare dry bio-iron flocculant powder, and then add it to arsenic-containing wastewater; make the ratio of bio-iron flocculant to arsenic content in the bioreactor 0.06-0.48g bio-iron flocculant: 1mg Arsenic can be purified by stirring for 2-8 hours.

[0036] Example 2:

[0037] The sludge was taken from a sewage treatment plant in Jimo City, Qingdao. It was digested sludge. Take 200mL of sludge, add 0.71g of ferrous sulfate and 0.4g of potassium nitrate, infuse with nitrogen for 30min, and incubate at 25℃ for 7d. Take 10mL sample from the above pre-culture sludge and add it to 200mL sterile NAFO medium: NH 4 Cl 0.28g/L, K 2 HPO 4 0.25g/L,MgSO 4 0.1g/L, CaCl 2 0.01g/L, 20mM sodium acetate, 15mM sodium nitrate, FeCl 2 ·4H 2 O 15mM, adjust the pH to 7.0. Fill the reactor with nitrogen for 30 minutes, and let it stand for 8 days at 25°C. After culturing, the sludge turns from black to yellow-brown, and the biological iron flocculant is prepared.

[0038] After NAFO cultivation, the apparent color of the sludge changed significantly, from the original black with foul smell to yellow-brown flocs, and the smell disappeared. The relationship between the microbial community before and after NAFO cultivation was constructed by high-throughput 16s rRNA gene sequencing. (Attached figure 1 ), the results showed that the microorganisms in the original sludge were mainly Burkholderiaceae (Burkholderiaceae), Caulobacteraceae (Caulobacteraceae), Gemmatimonadaceae (Bacomonas) and Ectothiorhodospiraceae (Exothiorhodospiraceae). , But the microorganisms in bioflocculants are mainly Xanthomonadaceae (Xanthomonadaceae), Chitinophagaceae (Spring hair fungi) and Bacilales Incertae Sedis (Bacillales), which means that after NAFO culture, the sludge The microbial community of the bio-iron floc has changed significantly, and the microorganisms that can induce the formation of bio-iron flocs can survive; in addition, the scanning electron microscope, X-ray diffractometer and Fourier infrared spectra of bio-iron flocs are attached figure 2 with 3; From the attached figure 2 It can be seen that the biological iron flocs are composed of NAFO cells and iron minerals, and most of the cells are wrapped by iron minerals. Energy spectrum analysis further shows that the iron content of the biological iron flocs is as high as 36.65%; X-ray diffractometer (XRD ) The results show that the mineral form of biological iron flocs is mainly composed of amorphous or weak crystalline iron oxides (attached image 3 a), Fourier spectrum (FTIR) at 468cm -1 There is a strong absorption peak, which also confirms the existence of iron oxides in the biological iron flocs (attached image 3 b).

[0039] The dry powder of the bio-iron flocculant prepared above was added to the arsenic-containing wastewater to further verify the repair effect of the flocculant on different types of arsenic. 0.03g of the bio-iron flocculant was added to 250ml of the three with a concentration of 0.5-2mg/L. The initial pH is 4.0, 5.5 and 7.5 respectively. Place the above-mentioned triangular flask in a shaker at 180rpm (25℃) and shake for 2h; then determine the remaining trivalent arsenic or pentavalent arsenic concentration in the solution, Calculate the removal efficiency of biological iron flocculant for trivalent arsenic or pentavalent arsenic; Figure 4 It can be seen that after 2 hours of reaction, both trivalent arsenic and pentavalent arsenic can be effectively removed, and the bio-iron flocculant has higher removal efficiency for trivalent arsenic and pentavalent arsenic under low pH conditions, and the initial pH is 4.0 at the same time. When the concentration is 0.5mg/L, the removal efficiency of trivalent arsenic and pentavalent arsenic are 97.4% and 90.3%, respectively. With the increase of arsenic concentration and pH, the removal efficiency of trivalent arsenic and pentavalent arsenic decreases. However, the removal rate is still greater than 65%, which means that the biological iron flocculant can effectively remove different types of arsenic. The biological iron flocculant prepared by the invention can be used for the repair of arsenic-containing wastewater.