Abstract
Industrial sludge is a by-product which is enormously generated in wastewater treatment plants. Constructed wetland for sludge treatment (CWST) is a low cost, effective technology. This study investigated the effect of various design and operation parameters on the efficiency of four pilot-scale CWSTs to determine the optimal parameters by using the Analytic Hierarchy Process (AHP) for Decision- Making. The wetland units were planted with Phragmites australis or Typha angustifolia, operated with four sludge loading rate (SLR) (50, 60, 70 and 80 L/m2) and monitored in six different hydraulic retention time (HRT) (2,5,7,9,12 and 14 days). AHP results provided the optimal key parameters (vegetation of P. australis, 14-day HRT, SLR of 60 L/m2) which gave the most effective sludge treatment, reducing 99.8%, 95.16% and 98.23% for COD, TKN and TP, respectively. The results also showed that HRT, SLR and vegetation remarkably affected to the efficiency of CWST. In addition, AHP is an effective method to determine the optimal design and operation parameters of CWST.
Highlights
INDUSTRIAL sludge management has become a matter of concern because of three reasons: (i) Sludge is a by-product with enormous volume and not expected but inevitably generated in the wastewater treatment [1]. (ii) In the composition of the industrial sludge containing hazardous substances such as heavy metals [1]. (iii) The cost of sludge treatment is tremendous to a wastewater treatment plant, accounting for 40-60% of the total cost of the wastewater treatment plant [1]
The Chemical Oxygen Demand (COD), Total Kjeldahl Nitrogen (TKN) and Total Phosphorus (TP) concentrations of the leachate were affected by both sludge loading rate (SLR) (P < 0.01) and hydraulic retention time (HRT) (P < 0.01) and there was a significant interaction between SLR and HRT to treatment efficiency according to the two-way ANOVA (P < 0.01)
Four pilot-scale Constructed wetland for sludge treatment (CWST) were operated with different four SLRs and HRTs from 2 days to 14 days and different vegetation, which provided whether SLR, HRT and vegetation significantly affected to the treatment efficiency
Summary
INDUSTRIAL sludge management has become a matter of concern because of three reasons: (i) Sludge is a by-product with enormous volume and not expected but inevitably generated in the wastewater treatment [1]. (ii) In the composition of the industrial sludge containing hazardous substances such as heavy metals [1]. (iii) The cost of sludge treatment is tremendous to a wastewater treatment plant, accounting for 40-60% of the total cost of the wastewater treatment plant [1]. INDUSTRIAL sludge management has become a matter of concern because of three reasons: (i) Sludge is a by-product with enormous volume and not expected but inevitably generated in the wastewater treatment [1]. Sludge becomes one of the major challenges for many countries in the world, it is necessary to have an alternative sludge treatment technology to ensure the performance and handling costs. Constructed wetland for sludge treatment (CWST) derived from Constructed Wetland has been applied successfully for over twenty years [2]. Advantages of CWST are the treatment efficiency and economic (investment and operation cost). It is known as a technology-friendly environment [3]. CWST consists of two main components, are available in nature: the filter material (sand, gravel...) and the vegetation; the majority of pollutants in sludge will be retained in CWST, and gradually be transformed into minerals, gas, another part is absorbed by plants, only a small
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