Biological Effects Of Livestock Wastewater Treatment By Using Environmental Biological Methods

As large scale livestock production develop rapidly, abundance of livestock excreta and all kinds of castoffs lead to a severe environmental pollution. It also becomes the restricted factor to develop itself. The pollutants from the livestock production are becoming the third source of pollution after industrial wastes and domestic garbage. The contaminants are composed of harmful gases from animal body, excreta, scraps and feathers, as well as the washing water from the livestock production factories. There are many methods to cope with the breed aquatics' wastes but not easy. Environmental biological ways have been proved to be the key methods to clean the livestock waste water. This paper is probing the biological effects of the aerobic microorganism and constructed wetland technology.The Aerobic biological technique aimed at studying the nitrogen removal under the shortcut nitrification-denitrification condition. The influences of the fators including pH, NH₄⁺-N Load, carbon nitrogen ratio (C/N) and dissolved oxygen (DO) in the SBR system on the HNO₂ accumulation were investigated. The method to achieve the shortcut nitrification-denitrification and how to reach a stable accumulation of HNO₂ by changing the running parameters in the SBR system were also explored.The constructed wetland was located in the sewerage-treat station of the teaching garden of Sichuan agricultural university. Phragmites australis and Alpinia aquatuca which has not been reported were used as wetlands treatment. Substrates are the purple soil, sands and gravels. It was investigated the nitrogen and phosphorus removal from this waste water, and two concentrations were studied to deal with the Phragmites australis: one was the original waste water and the other was diluted one time. We tested its physiological characteristics of the roots' activity, superoxide dismutase (SOD) and peroxidase (POD) as well as the content of malondialdehyde (MDA), chlorophyll and dissociated proline. And also reseach the changes of RAPD fingerprinting of Phragmites australis under the contamination stress in high concentration livestock wastewater. The results are summarized in the following.(1) When the pH value was too high, the activity of Nitrosomas will be affected and the accumulation of nitrite will decrease accordingly. The pH value affects the concentration of FA. When it was 8.5, the best denitrification purpose was achieved and the accumulation of nitrous acid is also high. When parameters of feed-water (such as concentration of ammonia nitrogen, bubble amount, and pH value) were well controlled, a relatively high load was favorable to the accumulation of nitrous acid and may result in a good denitrification effect. Too high an ammonia nitrogen load was good to nitrobacteria. However, would influence the activity of Nitrosomas. On the other hand, since Nitromonas was adapted to an environment with a high FA concentration, its activity will increase to a certain degree as well. With ammonia nitrogen load of feed-water, DO and pH value maintained, change of feed-water cod value will exert an influence on the accumulation of nitrous acid. When C/N=7, the amount of accumulated nitrous acid reaches a maximum. At this time, denitrification effect and COD removal rate are also the best.(2) In the SBR system, on the condition that F/M, C/N, pH, MLSS, and temperature remain constant, the concentration of DO was well correlated with that of three-nitric. When DO concentration was 3.0mg/L, the accumulation rate of nitrosonitro and the concentration of ammonia nitrogen in water discharge reach 85% and 0mg/L respectively. Favorable short-range nitifying and denitrifying purposes are obtained. With DO value kept under 2.0mg/L-7.0mg/L, the SBR system operates normally. When DO was at a concentration other than 7.0mg/L, removal rate of total nitrogen reaches 99% and that of COD maintains at about 95%, and the quality of water discharge is favorable.(3) The adsorption of phosphorus in the soil increased with the adding of oscillating time. Eight hours was the optimal oscillating time for sand and gravel's adsorption. The adsorption of phosphorus in the substrates do fit with the Langmuir, Freundlich and Temkin equations. Nevertheless the Langmuir equation was the optimum. Competition adsorption is non-existent in the three mixed substrates. The constructed wetland remove the Phosphorus was mainly by the adsorption of substrates. The adsorptive capacity was the soil＞sand＞gavel. In the constructed wetlands of sewage treatment plant, substrate adsorption to phosphorus increased along with the bed length. When the plants were applied to treat the waste water, the distribution of nitrogen and phosphorus was different in the root, stem and leaf. As for Alpinia aquatuca, its root was well in nitrogen adsorption, for Phragmites australis was aerial part. Phosphorus removal ability of Alpinia aquatuca was not good, especially in the simulated constructed wetlands. But the leaves of reed could efficiently remove phosphorus.(4) Wetland with plants were superior to unplanted in nitrogen and phosphorus's removal. Variance analysis showed that there was no significant variance among the different treatment, which means that the plants removal was not the key factors. And the complex plants-bed can remove more than the only one plant-bed (except for NO₂^--N).(5) In order to study the effect of the different concentrations on the removal efficiency, the inlets were mixed with the effluent of the flotation column and CASS pool in different proportions. At the proportion of 7∶3, TP got the best removal and NH₄⁺ -N at 5∶5, COD at 8∶2. The C/N also had an effect on the removal efficiency. In Phragmites australis bed, Alpinia aquatuca bed and multiplicity bed, NH₄⁺ -N had the best removal at 1∶1, 3∶1, 4∶1 respectively. When FeCl₃ was added in the substrates, the removal efficiency of TP increased with the increase of FeCl₃.(6) The ability of nitrification was the weakest, and denitrilfication intensity was the strongest in the 1/3 position of the constructed wetlands system. Velocity of nitrification and denitrification were both the fastest during the ftrst 8h. Intensity of nitrification and denitrification obviously had a phenomenon of stratification. The upper layer is better than the lower layer. And there was a negative correlation between the nitrification and denitrification rate. Denitrification intensity changed with different values of C/N in the study, and it could reach the maximum while C/N was 3. Through 6 months' water quality monitoring, the pollutants degraded along with the bed length. And the degradation was different with the times and positions. As for NH₄⁺ -N, the best removal was in August, and at the front part. And for TP, the best removal was in July, and at the aftering half part.(7) Effects of livestock wastewater on the physiological characteristics of leaves and roots were investigated under the stress of two concentrations of livestock wastewater——high and mid-concentration of livestock wastewater which was half diluted from the raw livestock wastewater. The results showed that the effects of two concentration livestock wastewater stress on the physiological characteristics of Phragmites australis were similar, but different in stress strength. The variability extent of each physiological index under long-term continuous stress of high concentration of raw livestock wastewater was greater than that of mid-concentration of livestock wastewater. This indicated that the physiological effects of high concentration livestock wastewater on Phragmites australis were stronger than those of mid-concentration livestock wastewater. Except for the content of malondialdehyde (MDA) and the activities of superoxide dismutase (SOD), other physiological indexes of Phragmites australis which was grown in the constructed wetland were significantly higher than those of Phragmites australis growing in the actual conditions of Fenjiang River.(8) The Activities of superoxide dismutase (SOD) significantly increased under the stress of livestock wastewater. The content ofperoxidase (POD) decreased at the beginning and then slowly restored to the previous level before stress. The activities of catalase (CAT) gradually decreased all the time. The variation tendency of the activities of POD showed that Phragmites australis were greatly hurt at the beginning and as the stress time continued Phragmites australis gradually adapted to the livestock wastewater with no harmful substance H₂O₂ largely accumulated. The activities of SOD significantly increased indicating that the body of Phragmites australis produced a great deal of active oxygen atom, and would inevitably produce H₂O₂ if clear off the harm brought by active oxygen atom, while the variation trend of the activities of POD and CAT showed that POD and CAT did not take effect that producing H₂O₂ by getting rid of the harm brought by active oxygen atom. So it could infere that Phragmites australis had another protection mechanism to get rid of the harm brought by H₂O₂ accumulation. This protection mechanism probably was relevant to some other non-enzyme protection system clearing away active oxide.(9) The activities of Phragmites australis roots significantly increased, the content of MDA gradually decreased and the content of praline kept steady at a lower level after rapidly decreasing under the stress of livestock wastewater. On the condition of stress of wastewater, the increasing activity of Phragmites australis roots contributed to resist harm from wastewater stress, and increase anti-oxidative abilities. The activities of Phragmites australis roots still keep at a higher level under nearly one month stress. This indicated that the growth condition of Phragmites australis was not greatly affected. MDA was the important product of the peroxidation of membrane. The gradual decrease of MDA showed that the cell membrane system of Phragmites australis was not strongly damaged under the stress of livestock wastewater, and the peroxidation of cell membrane was weak, which embodied that electrolyte leakage diminished, and permeability of cell membrane decreased. The decrease of proline content indicated that Phragmites australis were not able to actuate the accumulation mechanism of praline to enhance anti-adversity abilities under the stress of livestock wastewater. In other words, the damage was small, and Phragmites australis had a strong anti-adversity ability.(10) Content of chlorophyll presented a gradual decreasing tendency, while the value of chlorophyll a/b presented an increasing tendency under the stress of two concentration livestock wastewater. With the decrease of chlorophyll content, photosynthesis of leaves of Phragmites australis was partly affected, and the leaves of Phragmites australis had indication of growing old, but it didn't greatly affect the growth condition of Phragmites australis. The increase of chlorophyll a/b value was due to chlorophyll a increment more than that of chlorophyll b. In conclusion with it, chlorophyll a/b was relevant to chlorophyll a and chlorophyll b. And there was fixed scope of application to take chlorophyll a/b as the important index to measure the grown condition of plant leaves.(11) The results of the variation of physiological characteristics of Phragmites australis under the stress of livestock wastewater showed that the stress of high concentration and mid-concentration livestock wastewater had lower effects on the growth condition of Phragmites australis, and Phragmites australis showed stronger anti-adversity abilities. The results of RAPD PCR amplification using 160 primers showed that there were three primers displayed repeatable and different RAPD fingerprinting patterns in the existeing materials. The three RAPD primers were S74, S516 and S14, respectively. The results indicated that Phragmites australis mutated at molecular level under the stress of high-concentration livestock wastewater. The specific RAPD fragments caused by this mutation might closely link with the anti-polluted genes of Phragmites australis. The excellent growth performance of the plants under high-concentration livestock wastewater could be relevant to this gene mutation. This work will provide the basis for further research on revealing the molecular mechanism of strong anti-polluted capability of the plants on the constructed wetland.