Wastewater treatment refers to the process of treating sewage to meet the allowable discharge standards and then discharging it into the sewer. At present, there are generally two methods for treating laboratory waste liquid:
1. Reuse. Adopting a recycling water system enables the wastewater to be reused multiple times during the experiment, reducing the amount of wastewater discharged. Bosida laboratory wastewater treatment equipment purifies and treats laboratory wastewater before discharging it, protecting the environment and reducing pollution.
2. Purification treatment. Purification treatment involves using various methods to separate the pollutants contained in wastewater or convert them into harmless substances, thereby purifying the wastewater. There are generally three methods of purification:
(1) Physical methods: sedimentation, filtration, centrifugal separation, flotation (air flotation), mechanical retention, oil separation, extraction, evaporation crystallization (concentration), reverse osmosis, etc.
(2) Chemical methods: coagulation sedimentation, acid-base neutralization, oxidation-reduction, electrolysis, adsorption disinfection, etc. (3) Biological methods: activated sludge process, biofilm process, biological oxidation pond, sewage irrigation, etc. I. Treatment of Mercury-containing Waste Liquid
The allowable discharge concentration of mercury in the waste liquid is 0.05mg/L(calculated as Hg). The treatment methods are:
Treatment methods for laboratory waste liquid
Sulfide co-precipitation method: First, adjust the pH value of the waste liquid containing mercury salts to 8-10, and then add an excess of Na2S to generate HgS precipitate. Then FeS04(co-precipitating agent) is added to form FeS precipitate with the excess S2-, which adsorbs and co-precipitates the HgS particles suspended in water that are difficult to settle. Then it is left to stand, separated, and after centrifugation and filtration, the mercury content in the filtrate can be reduced to below 0.05mg/L.
2. Reduction method: Using copper shavings, iron shavings, zinc granules, sodium borohydride, etc. as reducing agents, metallic mercury can be directly recovered.
Ii. Treatment of Waste Liquid Containing Cadmium
Hydroxide precipitation method: Add lime to the waste liquid containing cadmium, adjust the pH value to above 10.5, stir thoroughly and let it stand to convert cadmium ions into insoluble Cd(OH)2 precipitates. After separating the precipitate, the Cd ions in the filtrate were detected by dithizone spectrophotometry (reduced to below 0.1mg/L), the filtrate was neutralized to a pH value of approximately 7, and then discharged.
2. Ion exchange method: By taking advantage of the fact that Cd2+ ions have a stronger binding force with cation exchange resins than other ions in water, they are preferentially exchanged. Iii. Treatment of Lead-Containing Waste Liquid
Add slaked lime to the waste liquid and adjust it to a pH value greater than 11 to cause lead in the waste liquid to form Pb(OH)2 precipitate. Then, Al2(SO4)3(coagulant) is added to lower the pH value to 7-8. Pb(OH)2 and Al(OH)3 will precipitate together. The precipitates will be separated. After meeting the standards, the waste liquid will be discharged.
Iv. Treatment of Arsenic-Containing Waste Liquid
FeCl3 is added to the arsenic-containing waste liquid to make the Fe/As ratio reach 50, and then the pH value of the waste liquid is controlled at 8-10 with slaked lime. Arsenic in the waste liquid is removed by the adsorption effect of the co-precipitation of new hydroxides and arsenic compounds. Let it stand overnight, separate and settle. After meeting the standards, discharge the waste liquid.
V. Treatment of Phenolic Waste Liquid
Phenol is a highly toxic cytoplasmic poison. Treatment method: For low-concentration phenol-containing waste liquid, sodium hypochlorite or bleaching powder can be added and boiled to decompose phenol into carbon dioxide and water. If it is a high-concentration phenolic waste liquid, it can be extracted with butyl acetate, then back-extracted with a small amount of sodium hydroxide solution. After adjusting the pH value, it can be distilled for recovery. The treated waste liquid is discharged. Vi. Comprehensive Waste Liquid Treatment
Adjust the PH of the waste liquid to 3-4 with acid or alkali, add iron powder, stir for 30 minutes, then adjust the pH to about 9 with alkali, continue to stir for 10 minutes, add aluminum sulfate or basic aluminum chloride coagulant, and carry out coagulation and sedimentation. The supernatant can be directly discharged, and the sedimentation is treated as waste residue.
