Retting Of Flax Biological Wastewater Treatment Process

The production of flax in Yunnan province has got fast development in the past years. At the same time, the majority of the wastewater from the factory were discharged freely to the environment without any treatment, even for those treated before discharge, the facility is always very simple, and the effluent can't meet the relevant standard, accident is inevitable. So it makes senses to have a deep study on the treatment of flax degumming wastewater.Local economic character was deeply considered in choosing a suitable technology for flax wastewater treatment, and the technique of hydrolyzation acidification following oxidation-ditch was chosen as it is cost effective, stable and easy to maintenance.Hydraulic conditions were analyzed in the process of reactor design. Analyses on velocity of flow, velocity distribution and resistance in ditch were emphasized for oxidation-ditch. The conclusion is as follows: Velocity of flow is related with water deep, and 0.17ms^-1 was believed to be reasonable for the experiment. Diffused aeration was employed for oxygen supply while drive system was installed on the bottom of the reactor. Aeration system and drive system were separated in order to get a perfect velocity distribution. Diversion walls ware set on sinuosity in the ditch to reduce the resistance.ACF32 (mixture of different microbial species) was chosen for flax sewage treatment in my experiment. Rhodospirillum in ACF32 can degrade BOD5 and COD effectively; nitrifying bacteria, denitrifying bacteria and phosphobacteria in ACF32 can get high efficiency of denitrification and dephosphrization. ACF32 also contains species capable of degrading lignin. Based on the advantages mentioned above, ACF32 were chosen to culture activated sludge.The conclusion shows that: for flax wastewater with BOD5 concentration between 3500 mgL^-1-4500 mgL^-1 COD concentration between 5400 mgL^-1 -7000 mgL^-1, TN concentration about 190 mgL^-1, TP concentration about 20 mgL^-1, PH between 4.5-5.5 and chroma between 250-800, high removal efficiency can be got with the technique of hydrolyzation acidification following oxidation-ditch. The COD concentration of effluent from hydrolyzation acidification reactor and oxidation-ditch reactor is 3000mgL^-1 and 200mgL^-1 respectively, with removal efficiency of 57% and 93% respectively, the totalremoval efficiency for COD reached to 97%. The concentration of TN in effluent is 20mgL^-1 compared to 190mgL^-1 in influent, with removal efficiency of 89%. The concentration of TP in effluent is about 2.5mgL^-1 compared to 20mgL^-1 in influent, with stable removal efficiency about 85%. The chroma removal efficiency reached to 69% though it still can't meet the relevant discharge standard.With the help of kinetic analyses, we computed the following parameters: 0.63 mgMLSS' mgCOD^-1 for yield rate(Y), 0.075d^-1 for endogenous-decay coefficient(K_d).In the process of cost-benefit analyses, data from practical project was applied for reference. The result shows that: unit cost is in inverse proportion to flux, with the increase of flux, the unit cost will fall accordingly. The relationship between unit cost and flux and be formulated approximately as follows: Y=16574X^-0.1988. The qualitative relations mentioned above also applies to unit operation cost.The innovations of the thesis are as follows:(1) The original or conventional activated sludge system is mainly focused on the treatment of a given wastewater with a given single species. In my experiment, multi-species have been employed for flax wastewater treatment, which is more applicable for practical project.(2) Biotechnology was employed based on the characteristic of flax wastewater. The technique of hydrolyzation acidification following oxidation-ditch, which is believed to be cost effective and stable, was chosen after comparison of different techniques.(3) All construct units of the system is designed and optimized based on sound analyzes on hydraulic conditions and principles of bio-degradation.(4) The experiment shows that high removal efficiency can be guaranteed with the technology we introduced, and it supplied a successful example for the combination of dominant species with conventional buildings.(5) Key kinetic parameters of dominant species were determined through kinetic analyzes.