دانلود رایگان مقاله حذف بیولوژیکی نیترات از آب و فاضلاب با فرایند نیترات سازی فاز جامد

Abstract

Nitrate pollution in receiving waters has become a serious issue worldwide. Solid-phase denitrification process is an emerging technology, which has received increasing attention in recent years. It uses biodegradable polymers as both the carbon source and biofilm carrier for denitrifying microorganisms. A vast array of natural and synthetic biopolymers, including woodchips, sawdust, straw, cotton, maize cobs, seaweed, bark, polyhydroxyalkanoate (PHA), polycaprolactone (PCL), polybutylene succinate (PBS) and polylactic acid (PLA), have been widely used for denitrification due to their good performance, low cost and large available quantities. This paper presents an overview on the application of solid-phase denitrification in nitrate removal from drinking water, groundwater, aquaculture wastewater, the secondary effluent and wastewater with low C/N ratio. The types of solid carbon source, the influencing factors, the microbial community of biofilm attached on the biodegradable carriers, the potential adverse effect, and the cost of denitrification process are introduced and evaluated. Woodchips and polycaprolactone are the popular and competitive natural plant-like and synthetic biodegradable polymers used for denitrification, respectively. Most of the denitrifiers reported in solid-phase denitrification affiliated to the family Comamonadaceae in the class Betaproteobacteria. The members of genera Diaphorobacter, Acidovorax and Simplicispira were mostly reported. In future study, more attention should be paid to the simultaneous removal of nitrate and toxic organic contaminants such as pesticide and PPCPs by solid-phase denitrification, to the elucidation of the metabolic and regulatory relationship between decomposition of solid carbon source and denitrification, and to the post-treatment of the municipal secondary effluent. Solid-phase denitrification process is a promising technology for the removal of nitrate from water and wastewater.

8. Concluding remarks and future

perspectives Solid-phase denitrification is a promising technique to remove nitrate from a variety of water and wastewater, including drinking water, groundwater, aquaculture wastewater, secondary effluent and wastewater with low C/N ratio. The types of carbon sources, temperature, DO levels and HRT play important roles in determining the denitri- fication rate and effluent quality, including the release of DOC and ammonium formation, nitrite accumulation and production of N2O and CH4. The selection of an appropriate carbon source is a tradeoff between their denitrification rate, availability and cost. Although a variety of natural materials were investigated for denitrification, woodchip would be attractive in practical application due to its low cost, long life-span of effectiveness and less adverse effects. Compared with the natural plantlike substrates, the synthetic biodegradable polymers exhibited better and stable denitrification performance. The availability of the cheap biodegradable polymers such as the wastes of the bioplastic industry is determinant for its application in commercial denitrification process. Studying the mass reduction rate of solid carbon materials to determine their renewal period is necessary in the continuation of the solid-phase denitrification. The post-treatment to remove the released DOC from the solid-phase denitrification needs to be further investigated for its practical application in drinking water. To date, solid-phase denitrification technique has been studied mostly on the laboratory scales except for in-situ groundwater remediation. The fact that a little research was reported on the performance of solid-phase denitrification in commercial systems is another drawback for its full-scale application. Regarding the bacterial community, most of the denitrif