The Transformation Of Nitrogen And Phosphorus Forms During Co-Composting Of Sewage Sludge And Straw Biomass.

The disposition and utilizition of urban sewage sludge is one of the serious environmen- tal problems in big citys all over the world. The compost and land utilizition of urban sewage sludge was a useful method to make it innoxious and resourceful. Fermenting sewage sludge at high temperature by aeorbic bacterium and oxygen (High Temperature Aeorbic Compost Technology) is an important approach to change solid organic waste into organic fertilizer of high-quality innoxiously and resourcefully. It not only solved the environmental problem caused by sewage sludge, but also was of great significance to develop organic fertilizer, preserve and improve soil fertility as well as enhance agricultural development sustainably. Some nitrogen and phosphorus were lost during the composting process in the degradation and transformation of organic matter. The transformation characteristics of nitrogen and pho- sphorus during the composting process were realized, which is important to control composting conditions and reduce nutrient losses.The objective of this study is to investigate the transformation of nitrogen and phosph- orus forms during co-composting of sewage sludge and straws in aerated static pile compost- ing system and natural ventilation fermentation system. With sewage sludge (SS) as raw materials, and wheat straw bran (WSB, particle size less than 0.5cm), wheat straw section (WSS, about 3cm length), maize straw bran (MSB, particle size less than 0.5cm) and maize straw section (MSS, about 3cm length) as conditioners in this study, the results were as following:1. There were three temperature stages including warming period, high temperature period and cooling period for each treatment. During the composting, the warming rate of the treatment adding the small diameter of the straw were higher than that of the treatment adding the large diameter of the straw. The high temperature period of the former was longer than that of the latter. Adding two different straw had no apparent impact on the changes of the moisture content and pH value. The EC of the treatment adding the maize straw was higher than that of wheat straw, but GI value has the opposite effect. For the same straw, moisture content, pH value, GI value of the treatment adding the small diameter straw changed with a more great range than those of adding the large diameter straw, but EC value has the opposite effect.2. The TN, NH4+-N and NO3--N content of the treatment adding the wheat straw changed with a more great range than those of adding the maize straw. For the same straw, the TN and NO3--N of the treatment adding the small diameter straw increased more than that of adding the large diameter straw. The former was more helpful to nitration reaction than the latter. The NH4+-N and the pH reached their maximum values at the same time. It was helpful to decrease the sustained high-temperature period for nitrification reaction.Adding two different straw had no apparent impact on the changes of the Total hydrolysable nitrogen, Ammonia nitrogen, Amino sugar nitrogen and Amino acid nitrogen. For the same straw, the Total hydrolysable nitrogen, Ammonia nitrogen, Amino sugar nitrogen and Amino acid nitrogen of the treatment adding the small diameter straw increased more than that of adding the large diameter straw. The HUN nitrogen of the treatment adding the wheat straw increased more than that of adding the maize straw, especially the small size of the straw.3. A considerable part of inorganic phosphorus converted into organic phosphorus along with the compost being maturity, which induces the content of organic phosphorus increased. Small sized straw added in compost as compost conditioner contributes to the inorganic phosphorus converting to organic phosphorus. Adding two different straw had no apparent impact on the changes of the TP. The available p and organic p of the treatment adding the wheat straw increased more than that of adding the maize straw, especially the small size of the straw.The Hedley classification method was used to study the various forms of inorganic phosphorus. The results showed that H2O-P, NaHCO3-P, NaOH-P, HCl-P and Residual-P were significantly increased in whole composting process. Adding two different straw had no apparent impact to the changes of the H2O-P and Residual-P. The NaHCO3-P content of the treatment adding the wheat straw changed with a more great range than those of adding the maize straw, but NaOH-P and HCl-P has the opposite effect. For the same straw, the H2O-P, NaHCO3-P, NaOH-P and HCl-P of the treatment adding the small diameter straw increased more than that of adding the large diameter straw. The Residual-P of the treatment adding the wheat straw section increased more than that of adding the maize straw bran.The Chang classification method was used to study the various forms of inorganic phosphorus. The results showed that various forms of inorganic phosphorus content dropped to the minimum at high-temperature period, but various forms of NH4Cl-P, Al-P, Fe-P, O-P and Residual-P were significantly increased in whole composting process. Adding two different straw had no apparent impact to the changes of the NH4Cl-P, NaHCO3-P, Fe-P, O-P, Ca-P and Residual-P. For the same straw, the NH4Cl-P and Residual-P of the treatment adding the small diameter straw increased more than that of adding the large diameter straw. The Al-P, Fe-P, O-P and Ca-P of the treatment adding the wheat straw section increased more than that of adding the maize straw bran.NH4Cl-P content of Chang classification method was higher than H2O-P content of Hedley classification method, but it was much smaller than the total content of H2O-P and NaHCO3-P of Hedley classification method. NaOH-P content of Hedley classification method was less than the total contents of Al-P and Fe-P of Chang classification method. There were no significant differences between Ca-P and Residual-P of Chang analysis with HCl-P and Residual-P of Hedley classification method. It showed that Hedley method was more reasonable in grading the modality of abiophosphorus between the two systems of grading the modality of abiophosphorus druing the compost process.