Application Research Of Advanced Anaerobic Technology In Printing And Dyeing Wastewater Treatment

Shaoxing Wastewater Treatment Plant (SWWTP) is responsible to treat municipal and industrial wastewater with a total treatment capacity of 700, 000 m³/d. Wastewater of SWWTP is mainly composed of 8% municipal sewage, 90% dyeing and printing wastewater and 2% other industrial wastewater. Being main component of SWWTP's wastewater originates from the alkali-decomposition processes of dyeing, printing, terylene artificial silk printing and dyeing wastewater (TPD wastewater), it is characterized by high pH (9.14-10.21), COD, color, SS (suspended solids) and low BOD/COD ratio (different from traditional printing and dyeing wastewater and municipal sewage). It belongs to the wastewater hard to be treated.In the past 4 years, SWWTP has well performed its responsibility and its effluent can be discharged below the discharging standard. However, WWTP have to be confronted with the sky-high wastewater treatment cost and thinking over the aerobic residual sludge disposal every day because of its predominant aerobic treatment unit. Under the condition of present energy resources are badly needed and deficient greatly of resources, the topic of sustainable development has become people's concerns. For its potential benefits of superior COD removal, lower sludge production and to cut down energy consumption, along with biogas generation, anaerobic digestion is a well established wastewater treatment technology, with worldwide application.The main purposes of this paper were to research the performance of application of advanced anaerobic technology in printing and dyeing wastewater treatment and cutting down the aerobic residual sludge of SWWTP. The key results from these studies are summarized as followings:Three kinds of different pilot-scale anaerobic reactors consisting of anaerobic baffled reactor (ABR), anaerobic plug flow reactor (APFR) and AnaEG were operated in the pilot-scale experiment of anaerobic technology. The average value of the diminished COD was 494, 393, 307mg/l or the average ratio of the diminished COD was 36.0%, 28.6% and 22.4%. The diminished BOD of AnaEG was 100 mg/l, while that of ABR and APFR was 8, 61 mg/L. All B/C were about or above 0.40, and were in the scope of easily biodegradation. Component of nutrient material changed very little. The ratio of C: N: P became better. The role of sulfate-reducing increased the concentration of sulfides/H2S in the anaerobic effluent, which heavily inhibited the Methanobacterium sp., and the methane produced little. The effluent of aerobic process after anaerobic could below the discharge standard.After cleaned and remedied, the average value of the diminished COD of anaerobic effluent in No.1 Stage of SWWTP was 165 mg/l. The diminished BOD was 40 mg/l, and the ratio of B/C increased. The diminished SO₄^2- was 70 mg/l and SS removed was 81 mg/l. The ratio of C: N: P became better. Influent and effluent pH was 9.58 and 8.51, and the variation range became narrow. According to the cost analysis, the practice of anaerobic in SWWTP would reduce the cost 4.90 million yuan per year.The degradation ratio of TA was 8.5% in the AnaEG,which showed that TA is hard to be decomposed under anaerobic conditions. The paper was to evaluate anaerobic treatment efficiency of reducing toxic compounds by gas chromatography mass spectrometry (GC-MS) analysis showed that a main component of the raw effluent was long-chain n-alkanes. Alkanes in the AnaEG could be reduced from 71.26% to 19.57%. The categories of the total organic components reduced from 112 to 64. AnaEG had a better degradation performance on the toxicity of long-chain n-alkanes which is toxicity to Methanobacterium sp. Three different toxicity tests showed that the wastewater had heavy toxicity, and AnaEG could reduce its toxicity.The sludge activity of the anaerobic sludge after digestion for one year in landfill was at its peak. It was the fittest seeded granular sludge and its adding could accelerate the star up of the reactor. SEM demonstrated the main microbial species of sludge in the three different sludges (granular sludge of landfill after digestion for 1 year; granular sludge of landfill after digestion for 0 d; granular sludge taken from the pilot-scale EGSB after operation 400 d) had obvious differences. However, denaturing gradient gel electrophoresis (DGGE) analysis of polymerase chain reaction (PCR)-amplified 16S rDNA gene fragments demonstrated a high degree of similarity of them. The particle size distribution demonstrated that there were some different between them. Three-step Model for the anaerobic granular sludge formation in sanitary landfill was put forward.The inversed sludge ratio of aerobic excess biomass recirculated to ABR could get 60% reduction in sludge production under aerobic conditions with effluent TCOD concentration well below the discharging limit of 150mg/L. High influent pH could promote the minimizing excess sludge production efficiency. The inverse ratio of the aerobic sludge recirculation to anaerobic reactor could reach 60% and 40% individually for the system with aerobic sludge retention time (SRT) of 10 d and 25 d. The distinct difference in sludge yield of aerobic and anaerobic/anoxic processes could explain the reason why it was different for different pH and aerobic SRT. Produce application presented that aerobic excess biomass in No.1 Stage of SWWTP could be reduced by 0.24 ton dry sludge/10,000 ton wastewater; No.1 Stage could reduce 2780 ton wet sludge per day.The aerobic TA degradation bacterium JD-1 was Pseudomonas aeruginasa, and anaerobic TA degradation bacterium JD-2 was Bacillus Cereus. JD-1 could degrade 1000 mg/L of TA in 24 h under aerobic conditions, and JD-2 could degrade 1000 mg/L of TA in 72 h. GC-MS analysis showed that their degradation approaches were different. One decolour facultative aerobes bacterium JD-3 isolated from AnaEG was Pseudomonas aeruginasa could degrade many kinds of azo-dyes of 100 mg/L in 72 h. Dyes were decoloured best under anoxic conditions.