Treatment of Livestock Wastewater by Bentonite Coated Chitosam

In this study a new type of flocculating agent-Bentonite Coated Chitosan was prepared to treat the livestock wastewater which came from the piggery. The bentonite coated chitosan was prepared of natural bentonite which was used as raw material and chitosan which was used as modifying agent. The raw concentration of the ammonia nitrogen and COD of the livestock wastewater were 1800~2200 mg/L and 2000~2100 mg/L. The study showed that the the best removal rate of them are 72.47% and 88.26% when the dosing quantities are 0.5g/L, stirring times are 20 min, stirring rates are 300 r/min, pH are 5, standing time are 60 min. The soil layer and shape of the chitosan did not changed after be modified.


INTRODUCTION
In recent years, livestock farm was developed to scale with the increasing demand of the livestock products.However the discharge of livestock wastewater is also increased (Jerz et al., 2011).Now the livestock wastewater is the primary pollution sources than industrial wastewater and domestic wastewater (Luting and Huafei, 2008).The livestock wastewater includes poultry excrement, piggery rinse water and so on Jinlian and Ning (2000).
This type of the wastewater has the advantages such as high concentration of the CODcr, the ammonia nitrogen and the SS (Jie, 2009;Zhiyong et al., 2007) .It will caused pollution surface water, underground water and farmland if random discharged (Xia et al., 2011).How to solve the livestock wastewater effectively is one of the most urgent problems to be settled especially during the twelfth five years plan that the ammonia nitrogen is added one of the water pollutant.
At present the livestock wastewater treatment are ABR (Shengqiong and Hongwang, 2011), SBR (Jian et al., 2009), USR (Sheng et al., 2011) and so on.However, these methods have the problems such as difficult to control, operation complicated, secondary pollution.This experiment prepared the bentonite coated chitosan which used natural bentonite as the raw material and chitosan as modifying agent to treat the livestock wastewater.In recent years the midified bentonite is used in the field of the heavy metals wastewater, organic wastewater and dyeing wastewater (Liping et al., 2010).It was a penetration that the Bentonite Coated Chitosan was used in the livestock wastewater firstly and the treatment efficiency was also proved in the study.

EXPERIMENTAL MATERIALS
The livestock wastewater used in the experiment was the effluent of a livestock farm in Shenyang Liaoning.The indexes of the livestock wastewater were showed in the Table 1.
The bentonite comes from the Heishan Liaoning.Its chemical constitute was showed in the Table 2.
The chitosan which decollation degree was 90% was dissolved with 5% (v/v) acetic acid solution in the 100 mL beaker.50 g of the bentonite coated chitosan was stirred with 50~60 mL of the chitosan solution and putted in the microwave oven under 800 w for 5 min, heated, porphyrized, selected through 0.18 mm (Hong et al., 2009a).

METHODOLOGY
The bentonite coated chitosan was putted into livestock wastewater of 500mL, changed the pH and

RESULTS AND ANALYSIS
The effect of the dosing quantity: The livestock wastewater was treated at the conditions of the concentration of the pH was 5, the stirring rate was 300 r/min, the stirring time was 20 min and the standing time was 30 min.The effect of the dosing quantity was shown in the Fig. 1. Figure 1 indicated that the removal rate of the ammonia nitrogen increased with the increase of the dosing quantity and meet the max when the dosing quantity was 0.2~0.5 g.The removal rate of the COD changed little at the removal rate of 45%.This was because the negative charge on the pollutant was neutralized by the bentonite coated chitosan and subsided at the function of adsorption bridge (Hong The effect of the pH: The livestock wastewater was treated at the conditions of the concentration of the dosing quantity was 0.5 g, the stirring time was 20 min, the stirring rate was 300 r/min and the standing time was 30 min.The effect of the pH was shown in the Fig. 2. Figure 2 indicated that the pH had a big impact on the removal rate of the ammonia nitrogen which the best treated effect was 6.This was because the pH had impact on the organic polymer adsorbent and the properties of the charge on the surface of the bentonite coated chitosan.At low pH value, there was more hydrogen ion which would compete with the ammonia ion in the bentonite coated chitosan.It was not good for the adsorption of the ammonia nitrogen.At high pH value, the surface of the adsorption was jammed easily (Hong et al., 2010).The impact on COD was not significant.The highest removal rate occurred when pH was 5.

The effect of the stirring time:
The livestock wastewater was treated at the conditions of the concentration of the dosing quantity was 0.5 g, the pH was 5, the stirring rate was 300 r/min and the standing time was 30 min.The effect of the stirring time was shown in the Fig. 3.
Figure 3 indicated that the removal rate of the ammonia nitrogen and COD increased firstly and decreased with the increase of the stirring time.The biggest removal rates were occurred when the stirring time was 20 min.This was because the adsorbent was saturate and the adsorbent would be destroyed if last the stirring time.So the proper stirring time was 20 min in this experiment.
The effect of the stirring rate: The livestock wastewater was treated at the conditions of the concentration of the dosing quantity was 0.5 g, the stirring time was 20min, the pH was 5 and the standing time was 30 min.The effect of the stirring rate was shown in the Fig. 4. The effect of the standing time: The livestock wastewater was treated at the conditions of the concentration of the dosing quantity was 0.5 g, the stirring time was 30min, the stirring rate was 300 r/min and the pH was 5.The effect of the standing time was shown in the Fig. 5.
Figure 5 indicated that the impact of standing time on ammonia nitrogen and COD were same approximately and the removal rate of them increased with the increase of the standing time.The removal rates did not changed if the standing time was more than 60 min.The ammonia nitrogen and COD were adsorbed and floated in the water sample after stirring.These adsorbent sinked under the gravity and the function completed when the standing time was 60min.So the proper standing time was 60 min in the experiment.
The single factor experiment indicated that the optimum process parameters of the livestock wastewater which treated by bentonite coated chitosan was the dosing quantity: 0.5 g, the pH: 5, the stirring time: 20 min, the stirring rate: 300 r/min and the standing time: 60 min The orthogonal experiment: The table of the orthogonal experiment of L16 (4 5 ) was build base on the single factors of the concentration of the dosing

Fig. 1 :
Fig. 1: The effect of the dosing quantity

Fig. 3 :
Fig. 3: The effect of the stirring time et al., 2009b).Considering the removal rate of ammonia nitrogen and COD, the proper dosing quantity was 0.5 g.

Fig. 4 :
Fig. 4: The effect of the stirring rate

Table 1 :
The indexes of the raw livestock wastewater

Table 3 :
The result of the orthogonal experiment