About half the population in developing countries lack safe excreta disposal facilities. Improper wastewater disposal contaminates groundwater resulting in spread of water related diseases such as typhoid, cholera, dy...About half the population in developing countries lack safe excreta disposal facilities. Improper wastewater disposal contaminates groundwater resulting in spread of water related diseases such as typhoid, cholera, dysentery. This research experimentally tested the applicability of charcoal and saw dust packed membranes as sewage purifiers for on-site sanitation systems like, septic tanks, cesspool, pit latrines, pour-flush pit excreta systems. Tests for E. coli, COD and BOD of the influent which was raw sewerage from sewers and effluent from layered saw dust and charcoal purifying materials experimental setup were separately carried out. The layers were varied from 150 mm, 200 mm and 300 mm with 150 mm layers of gravel in between. The experimental tests showed that 300 mm charcoal layers with a 150 mm gravel middle layer, reduced E. coli from 4800×1014 CFU/100ml to 1.08×104 CFU/100ml, BOD5 from 698 mg/l to 0.5 mg/l, COD from 1492 mg/l to 3.0 mg/l against environmental standards of 1.0×104 CFU/100ml, 50 mg/l, and 100 mg/l respectively and its efficiency is directly proportional to thickness of charcoal dust layers. In conclusion, introducing a lined purification chamber with layers of charcoal dust between the on-site sanitation system and soak pit will eliminate the pollution of ground water.展开更多
This paper studies a stochastic endogenous growth model with pollution. It introduces government expenditure and exogenous pollution abatement technology to eliminate pollution and proves that under appropriate equili...This paper studies a stochastic endogenous growth model with pollution. It introduces government expenditure and exogenous pollution abatement technology to eliminate pollution and proves that under appropriate equilibrium conditions the main economic indexes （including economic growth rate, the optimal government expenditure rate） in the centrally planned economy and decentralized economy can be expressed by the parameters of the model uniquely. The optimal tax policy is analyzed ,and the optimal pollution is derived.展开更多
文摘About half the population in developing countries lack safe excreta disposal facilities. Improper wastewater disposal contaminates groundwater resulting in spread of water related diseases such as typhoid, cholera, dysentery. This research experimentally tested the applicability of charcoal and saw dust packed membranes as sewage purifiers for on-site sanitation systems like, septic tanks, cesspool, pit latrines, pour-flush pit excreta systems. Tests for E. coli, COD and BOD of the influent which was raw sewerage from sewers and effluent from layered saw dust and charcoal purifying materials experimental setup were separately carried out. The layers were varied from 150 mm, 200 mm and 300 mm with 150 mm layers of gravel in between. The experimental tests showed that 300 mm charcoal layers with a 150 mm gravel middle layer, reduced E. coli from 4800×1014 CFU/100ml to 1.08×104 CFU/100ml, BOD5 from 698 mg/l to 0.5 mg/l, COD from 1492 mg/l to 3.0 mg/l against environmental standards of 1.0×104 CFU/100ml, 50 mg/l, and 100 mg/l respectively and its efficiency is directly proportional to thickness of charcoal dust layers. In conclusion, introducing a lined purification chamber with layers of charcoal dust between the on-site sanitation system and soak pit will eliminate the pollution of ground water.
基金Supported by the National Natural Science Foundation of China （70271069）.
文摘This paper studies a stochastic endogenous growth model with pollution. It introduces government expenditure and exogenous pollution abatement technology to eliminate pollution and proves that under appropriate equilibrium conditions the main economic indexes （including economic growth rate, the optimal government expenditure rate） in the centrally planned economy and decentralized economy can be expressed by the parameters of the model uniquely. The optimal tax policy is analyzed ,and the optimal pollution is derived.
