| Summary: | 碩士 === 國立屏東科技大學 === 環境工程與科學系所 === 99 === This study utilized treated pig excretion from the ranch at National Pingtung University of Science and Technology as nutrient source to study the optimum growth condition for algae in 5 L incubator. Concentrate algae solution was provided by Taiwan Algae Co. Ltd. Two experiments were conducted in the present study; Experiment 1 studied the effect of different amounts of CO2 on the growth of algae in treated pig wastewater whereas effect of various treated pig wastewater on the growth of algae was determined in Experiment 2. Two experiments had similar incubation conditions as follows: pH 7.0, temperature 25°C, continuous lighting, stirring at 20 rpm and incubated for 72 h. In Experiment 1, there were four different CO2 treatment groups which were 0 L CO2/min, 1 L CO2/min, 2 L CO2/min and 3 L CO2/min. In Experiment 2, there were two differently treated pig wastewater as nutrient source: aerobically and anaerobically treated wastewater and both incubated under 1 L CO2/min condition. Each treatment in both experiments had four replicates and sampling was done at 0, 12, 24, 36, 48, 60 and 72 h; algae growth and DM, NH4+-N , NO3--N, PO43--P , BOD , COD , ORP , conductivity and minerals (Fe, Mn, Zn, Cu, K, Ca and Mg) were analyzed.
Results in Experiment 1 showed that algae in 2 L CO2/min treatment, between the 24th until 72nd h of incubation, NO3--N utilization of algae was reduced from 363.75 mg/L to 260.57 mg/L. In 1 L CO2/min treatment, between 0 to 60th h, NH+4-N was reduced from 2.05 mg/L to 1.64 mg/L. In 0 L CO2/min treatment, the effect on PO43--P was better than other treatment groups between 0-72 h, dropping from 0.40 mg/L to 0.33 mg/L, indicating that with or without N source supplementation did not affect it’s utilization. Under different nutrient N sources, optimum algae utilization effect occurred in different treatment groups. Overall, N source supplementation treatment groups had better effect, in 1 L CO2/min treatment group at 60th h, its DM was 3.19%, significantly different (P<0.001) from other treatment groups; comparing with 0 h, its growth achieved 61.00%. For water quality index on the effect of water purification, in the four treatment groups, BOD and COD tend to decrease as incubation period increased.
Results in Experiment 2 showed that algae in aerobic and anaerobic treated pig wastewater, NO3--N content was 16.74 mg/L and 0.36 mg/L, respectively, and was significantly different (P<0.001). NO3--N content in pig wastewater was very important of algae growth. Under aerobic treatment, algae growth rate increased as incubation period increased, and until 72 h, algae DM was 2.34%. In anaerobic treatment, algae growth rate did not incraese and mortality seemed to occur. For water quality index on the effect of water purification, between 0-60 h of incubation, BOD in aerobic treated pig wastewater decreased from 144mg/L to 13 mg/L, causing high oxygen dissolved in the water; between 0-72 h of incubation, COD was decreased from 700 mg/L to 578 mg/L. In anaerobic treatment, COD was reduced from 1060 mg/L to 848 mg/L. During incubation, data from the two treatment group were stable and continuous reduction was observed after 72 h, water purification effect was excellent.
The study have proven that livestock wastewater contained high concentrations of organic substances, nutritious N source and microelements. Properly treated wastewater could be used to grows algae and algae growth was optimum under appropriate lighting, temperature and pH condition for photosynthesis, and achieving the objective to reduce CO2 and water purification.
Key Words: CO2, algae, pig wastewater, water quality index
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