Abstract
A constructed wetland system, consisting of a surface-flow wetland cell connected in series with three vertical subsurface-flow wetland cells, was tested for treatment of domestic sewage from rural families in southern China. Diatomite, vermiculate, zeolite and hydrotalcite, were used, respectively, as filler adsorbents in the sequenced subsurface-flow cells for adsorption of organic, cationic and anionic pollutants. Selected trees, shrubs and annual herbs were planted to form a wetland plant community. The total treatment capacity, hydraulic loading rate and water retention time were 2 m3/d, 0.5 m/d and 48 h, respectively. Experimental data obtained from a year operation confirmed that the treatment process followed the dynamic pathway of pollutant transformation. The constructed system was effective to remove TSS, CODCr and BOD5 and their effluent concentrations met the first grade of the discharge standards legislated in China. The removal rates of TN, NH3-N and TP were relatively lower, and their effluent concentrations fell within the range between the first and second grade of the standards. An increase in initial pollutant loading and a decrease in temperature in winter caused apparent accumulation of TN, NH3-N and TP in the system. Discharge of sludge at adequate intervals was shown to be effective to enhance the treatment efficiency.
Highlights
Accounted for by its low construction and operation costs and ecologically responsible nature, constructed wetland technology (CW technology) has been rapidly developed as one of the alternative solutions for treatment of various types of wastewaters in different countries [1,2,3,4,5,6,7]
There are numbers of factors affecting the treatment process, the hydraulic loading rate (HLR, the volumetric flow rate divided by the wetland surface area) and water retention time (HRT, the ratio of the useable wetland water volume to the average flow rate) are the two key parameters that need to be determined for the design of a constructed wetland treatment system
The observed observed changes changesin in effluent effluent concentrations concentrations(Table
Summary
Accounted for by its low construction and operation costs and ecologically responsible nature, constructed wetland technology (CW technology) has been rapidly developed as one of the alternative solutions for treatment of various types of wastewaters in different countries [1,2,3,4,5,6,7]. In order to obtain a better understanding of pollutant removal mechanisms, studies have been carried out by different workers on factors that determine the treatment efficiency of constructed wetland systems, including wetland types and combinations [5,10]; hydraulic and pollutant loads [2,11]; plant species [12,13,14]; substrates [15,16]; and their interactions [17,18], etc. Aimed at providing useful information for future design, efforts have been made in the following areas: dynamic simulation models [19,20,21,22]; treatment stages [23] and pollutant
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
