The Flocculation Research Of Paint Wastewater With Microbiology

With the development of modern painting process, spraying dosage is increasing, however, there is a lot of spray coating which named overspray can’t deposit on to workpiece. Sprayed paint go into the tank through a circulating water, and then flocculate. Conventional flocculants have some shortcomings, such as a large amount of slag, non-biodegradable and toxic. But microbial flocculant is a safe, non-toxic and biodegradable natural metabolite produced by bacteria, fungi, yeast and alga in their growth. Its main components are polysaccharide, protein, lipid, glycolipid, nucleic acid and glycoprotein, et al. It can make the bacteria cells, suspended particles and colloid particles to flocculation and sediment and it has been a research hot spot in the current world of water treatment agent.First, the strain was obtained through the separation and filtration which is named as FL-2. According to the physiological and biochemical experiments and16S rDNA sequence alignment, the strain FL-2has a100%confidence level with Acinetobacter lwoffii, and they are located at the same branch on the phylogenetic tree, which proves that the FL-2belongs to Acinetobacter lwoffii. In addition, the study of growth curve of FL-2shows that it is almost no lag phase, and at60h it begins to enter into the decline phase; kaolin suspension flocculation experiments find that only flocculant producted at72h has the highest flocculating rate, which can reach to87.68%.Second, the single factor experiment and the response surface experiment were conducted successively for optimizing culture medium and culture conditions of strain FL-2. The cultivation conditions of the strain FL-2with the highest rate of kaolin suspension flocculation are determined by single factor experiments, which is30℃, pH=9, and shaking speed of160r/min; the compositions of culture medium are glucose as carbon source, NaNO3, NH4Cl and urea as mixing nitrogen source, magnesium sulfate as inorganic salt.Third, the component content and structural properties of microbiological flocculant FL-2were analysised. According to the analysis of the qualitative and quantitative experiments and flocculation experiment, it mainly includes polysaccharide and protein, and they mainly exist in the extracellular. Through analysing the IR and UV spectrum, flocculant FL-2molecule mainly contains hydroxyl, carboxyl, amino, hydrogen bonds and so on, but no nucleic acid.Then, a series of flocculation experiments were carried out using the microbial flocculant FL-2and Jelly bacillus for paint fog wastewater and the flocculation mechanism is also investigated. The conclusions are as follows:at the condition of pH12-13, the adding volume of flocculant5mL and3mL, and no coagulant aid, the removal rate can reach93.02%and93.23%. When adding0.1mol/L3%CaC12and MgSO4on the flocculating rate increase to a certain extent, but inorganic salt can make environmental secondary pollution, so when emissions requirements is not very high, it can choose not to add it. Besides, at the temperature range of20and80℃, flocculant can keep good flocculation effect. Flocculant FL-2has quantities of-OH,-COO-,-NH groups, which makes it extremely easy to generate hydrogen bonding with the H+and OH-on the surface of paint fog particles to realize flocculation effect. Meanwhile, a large of-COO-are combined with the metal cations released from paint fog through ionic bond, thus forming floes.Last, the compound of FL-2and bacillus to flocculate the paint mist were studied. It concludes that the best solution:when firstly adding2mL bacillus, then adding2mL FL-2, finally Flocculating rate reached96.19%, but when this two kinds of bacteria compound with Inorganic flocculant, it was not good.