Study On Anammox Treatment Of Turtle Quaculture Wastewater And Its Microbial Mechanism

Turtle aquaculture is a major Chinese agricultural industry in rural area especially in the Yangtze River Delta. Using greenhouse to breed turtle was the main way of turtle aquaculture which conducted in the closed and constant temperature environment. The high-protein fish meal was used as main feed for turtles to keep them growing rapidly. However, a lot of high-protein feed was directly accessed to the aquaculture wastewater because of low efficiency of utilization. Therefore, the greenhouse turtle breeding wastewater contained relatively high content of nitrogen. In the intensive areas of turtle aquaculture, the greenhouse turtle breeding wastewater riched in nitrogen was usually discharged into rivers and lakes without any treatment, and caused the eutrophication of the reciving water bodies. The unordered discharge of greenhouse turtle breeding wastewater has brought hurt to the daily life and production safety of the surrounding residents. Also, the current situation caused limits sustainable development of the turtle aquaculture. According to the on-the-spot investigation of the feed way and wastewater quality of greenhouse turtle aquaculture in the typical rural greenhouse turtle breeding farms, then designed a greenhouse turtle breeding wastewater treatment technology based on Anaerobic Ammonium Oxidation (Anammox). Solved the problem in long start-up time of Anammox reactor and low specific growth rate of Anammox bacteria, the Anammox greenhouse turtle breeding wastewater treatment process was valid and stable. Primary results were summarized as follows:1. Based on the on-the-spot investigation of twenty typical rural greenhouse turtle breeding farms in four towns of Hangzhou, the turtle aquaculture almost adopted in the isothermal (the temperature was maintained at30±1℃and airtight greenhouse. The aquaculture density was around25-30turles per square metres. Two wastewater discharged ways were used in the farms which were particial drain and entire drain. The greenhouse turtle breeding wastewater was yellowish-brown or dark green, and pH was range from4.89to8.90. The SS, COD, ammonium, TN and TP concentration were changed greatly within the range600-1200mg L"1,18.1-612.0mg L-1,0.6-207.8mg L-1,6.3-275.0mg L-1and0.8-100.4mg L-1,respectively. The greenhouse turtle breeding wastewater contained relatively high ammonium and low COD.92.2%of wastewater C/N ratio was below4. Above all, the greenhouse turtle breeding wastewater was one kind of low C/N ratio wastewater. 2. Three Upflow Anaerobic Sludge Blanket (UASB) reactors were compared for Anammox enrichment using synthetic wastewater with Spherical Plastic (SP) and Bamboo Charcoal (BC) addition, and without carrier (CK). After four months of operation, the Anammox activity occurred in all reactors allowing continuous removal of ammonium and nitrite. Ammonium and nitrite removal efficiencies were all higher than98%in steady phase with the effluent concentrations below1mg L-1. According to the concentration of effluent ammonium, the processes occurred in all the three reactors could be divided into phases of sluggish, expressive, enhanced and steady. The UASB anammox reactor strewed with black sludge in the initial of the operation. However, the color of the biofilm changed into pale yellow and then reddish brown with the operation time.The start-up time could be shortened from117d and97d in CK and SP reactor to85d in BC amendment reactor. BC addition could accelerate the start-up of Anammox, the start-up time of the BC amendment reactor could be dramatically shortened for32and12d compared with the CK and SP reactor. The stoichiometric ratio of NO2--N consumption to NH4+-N consumption in the steady phase were1.12±0.11、1.14±0.11and1.17±0.12in CK, SP and BC rector, respectively. And the ratio of nitrate production to ammonium consumption were0.11±0.04、-0.02±0.06and-0.04±0.06in CK, SP and BC rector, respectively. Both of the ratio were smaller than well-accepted value. The main reason might be nitrification, denitrification and Anammox might coexist in BC, SP and CK reactor.3. To track Anammox bacteria in the three reactors, FISH and Q-PCR analyses for all Anammox bacteria were carried out on the operation days. The number of Anammox bacteria in all reactors increased with time during the whole start-up process, which was consistent to the removal rule of anmmonium and nitrite. On day123of steady phase, the Anammox cells in the sludge of CK, SP and CK accounted for23.3%,32.6%and43.7%, respectively. The number of Anammox bacteria16S rRNAgene copies was25.64±2.76×107,47.12±2.76×107and577.99±27.25×107copies g-1VSS in the sludge of CK, SP and CK, respectively. On day123, which represented the steady phase, the percentage of Anammox bacteria in BC reactor was1.86times and1.34times higher than that of CK and SP reactor, respectively. The number of Anammox bacteria16S rRNA gene copies in BC reactor was around22.5times and12.3times greater than that in CK and SP reactor, respectively. In addition, the max specific growth rate and minimum td were0.064d-1and10.8d in BC reactor. The max specific growth rate of anammox bacteria in BC reactor was1.78times and1.88times greater than that in CK and SP reactor, respectively. BC addition significantly increased the Anammox bacteria number in the UASB reactor which resulted in the acceleration of the Anammox start-up process4. The anaerobic ammonium removal from greenhouse turtle breeding wastewater was investigated using SP and BC anammox reactor. The result demonstrated that the nitrogen removal from greenhouse turtle breeding wastewater could be performed successfully. During the entire experiment, the anmmonium and TN removal efficiency was almost higher than85%, while the COD removal efficiency was higher than56%. The TN removal efficiency of BC reactor was a little higher than SP reactor. Based on the nitrogen and carbon balance in the process, the average anammox contribution to nitrogen removal was75.7-86.8%. Anammox was always dominant when fed with COD concentration varied from194.0mg L-1to577.8mg L-1. The fermentation was the main way to remove COD and the removal efficiency was around67.22-76.92%. Based on PCR-DGGE analyses, the results revealed that the Planctomycete, Proteobacteria, Chloroflexi, Chlorobi bacteria etc. were coexisting in the UASB reactor. A part of Planctomycete could be tolerated high content of organic carbon. The main reason might be these Planctomycete could utilize or metabolize the organic carbon, and that should be discussed continusly in future research.