Posted May 19, 2016 by admin in Natural Resource Management | 27 Total Views
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STUDIES ON PHYTOREMEDIATION AND SYSTEM VARIATION TO ENHANCE CONSTRUCTED WETLAND EFFECTIVENESS IN PROCESSING WASTEWATER CONTAINING HEAVY METAL

HEAD OF RESEARCH TEAM : Dr. Devi N. Choesin
TEAM MEMBERS : Dr. Iriawati, Viky Vidayanti M.Si, Wisya Aulia, S.Si, Miranti Prima Asri, S.Si.
OFFICIAL ADDRESS : SITH ITB, Gd. Lab. Tek. XI, Jalan Ganesa No. 10 Bandung
EMAIL : devi@sith.itb.ac.id

Background

Pollution of water and soil by various agents, especially due to industrial activity, is an environmental problem that must be seriously addressed. Phytoremediation provides an alternative approach to waste management that is effective, inexpensive, and environmentally friendly. This technique uses plants to remove or decrease the toxicity level of pollutants in the environment. The application of plants in phytoremediation is generally integrated with the use of constructed wetland systems. These man-made systems are designed to mimic the process of water purification by natural wetlands through elimination of certain organic and inorganic compounds. Heavy metals are among the pollutants that are increasingly being found in the environment as a result of various human activities.

The general objective of this research was to examine more closely aspects of phytoremediation and the optimization of constructed wetland systems in treating waste containing heavy metals, in this case chromium (Cr) and acid mine drainage (AMD) pollution as case examples. The research consisted of three separate experiments; all of which were aimed at the above general objective. The specific objectives of the experiments were to: (1) measure effectiveness of Typha angustifolia as heavy metal accumulator of chromium (Cr) and analyzing Cr speciation and distribution in the plant; (2) determine the effects of substrate variation (specifically the use of coconut shell charcoal and activated charcoal) to improve effectiveness of artificial wetland system in treating wastewater containing Cr; and (3) determine the effects of water flow (vertical or horizontal) and addition of sulfate-reducing bacteria on the effectiveness of a constructed wetland system in treating AMD.

Methodology

Experiment 1. Hydroponic media with and without the plant Typha angustifolia were given the addition of 0, 1, 5, 10 and 20 mg/L of Cr(VI) (K2Cr2O7). Total Cr concentration in media, media and room  temperature,  light  intensity,  humidity,  pH,  total  dissolved  solids  (TDS),  and conductivity were measured during 15 days retention period. Total Cr, analysis of distribution and speciation of Cr at the root and shoot of T. angustifolia were measured after 15 days of treatment. Rate of Cr decline in water media and bioconcentration factor (BCF) were then calculated. Experiment 2. Experiments were conducted to compare five different systems treated with simulated Cr wastewater, i.e., system 0 as a control system containing only wastewater; system 1 containing the plant Pistia stratiotes; system 2 containing 100% soil substrate and Pistia stratiotes; system 3 containing 75% soil + 25% coconut shell charcoal as substrate, and Pistia stratiotes; and system 4 containing 75% soil + 25% coconut shell activated charcoal as substrate and Pistia stratiotes. Each system was exposed to simulated waste from K2Cr2O7  with total Cr concentration of 15 mg/L for 15 days. In the varied systems, physicochemical factors and heavy metal content before and after treatment in aqueous media, substrate and biota (plant) were measured. To determine the mechanism of absorption of heavy metals by T. angustifolia, the distribution and speciation of Cr in plants were determined by X-ray fluorescence (XRF) and X- ray absorption spectroscopy (XAS). Total Cr concentration in the samples was measured by Atomic Absorption Spectrophotometer (AAS). Experiment 3. The constructed wetland system was designed in the form of a glass container measuring 35x20x30 cm (length x width x height), planted with Cyperus papyrus on substrate consisting of three layers, i.e., soil, sand and gravel (except the control system). The study compared five different systems: system 1 is a vertical-type system without the addition of bacteria; system 2 is a vertical-type with the addition of bacteria; system 3 is a horizontal-type without the addition of bacteria; system 4 is a horizontal-type with the addition of bacteria; and 5 is a control system containing AMD without water flow, bacteria addition, substrate, or plants. All systems were given AMD waste for 15 days.

Main Results and Conclusions

Experiment 1. Results showed that the remaining concentration of Cr in media containing T. angustifolia (37.87  to 65.74%) were significantly lower (p<0.05)  than in media without  T. angustifolia (64.01 to 81.64%). The decline rate of total Cr in media containing T. angustifolia (2.28 to 4.14% per day) were higher (i.e., faster) than in media without T. angustifolia (1.22 to 2.40% per day). Measurements of total Cr in root and shoot of T. angustifolia showed that Cr accumulation in roots (287.16 to 4399.79 mg/kg) was higher than in in shoots (234.02 to 1157.28 mg/kg). Based on Cr accumulation in T. angustifolia, BCF was calculated to range from 285.73 to 523.06. Analysis of Cr distribution indicate that Cr was detected in almost all parts of T. angustifolia root and shoot, but at different intensities. The species of Cr in the root and shoot of T. angustifolia was found to be Cr(III); a reduced form of Cr(VI) which is more stable and less toxic than Cr(VI). From overall results of this study, it can be concluded that: (1) T. angustifolia has moderate potential to absorb and accumulate Cr, based on the level of Cr accumulation (up to 1000 mg/kg) and BCF (1000 > BCF > 250); and (2) T. angustifolia has phytostabilization and rhizodegradation abilities as phytoremediation mechanisms, based on the distribution and speciation of Cr. Experiment 2. All systems were effective in reducing total Cr concentration. The control system reduced the lowest percentage of total Cr, i.e., 97.4%, while system 4 reduced the most total Cr, i.e., 97.8%. However, the reduction in total Cr was not significantly different among systems (p>0.05). Soil substrate accumulated the highest total Cr, with total Cr accumulation of 12.7%; however, the effectiveness of soil, charcoal, and activated charcoal were not significantly different (p> 0.05). Based on the results, it could be concluded that the addition of activated charcoal and charcoal to the soil substrate did not affect the system’s effectiveness in reducing total Cr concentrations in water within a period of 15 days; however there were significant differences in Cr concentration reduction measured at 3-day periods. Moreover, the addition of activated charcoal and charcoal did not affect the accumulation of Cr in Pistia stratiotes or in substrate. Experiment 3. Measurement results indicate that system 4, the system with horizontal flow and addition of bacteria was most effective in treating AMD waste. System 4 decreased Fe content in AMD by about 97.8 % and Mn content by about 90.8 %, and increased the pH value to 6.8. This system reached the standard quality for maximum permitted concentrations in the shortest period of time compared to other systems. System number 1 reduced Fe levels by 79.4% Fe and Mn levels by 76.5%, and increased the pH to 5.8. System number 2 decreased Fe levels by 92% and Mn by 89.2%, and increased the pH to 6. System number 3 decreased Fe levels by 87% and Mn levels by 83.4% and increased the pH to 5.9. Meanwhile, in system 5 (control), Fe and Mn levels, as well as pH, remained relatively constant. Overall results suggest that the horizontal- type design is more effective than vertical-type, and addition of bacteria can enhance system performance in processing AMD.

Results from all three experiments confirmed the effectiveness of constructed wetland systems in reducing heavy metal content in polluted waste.

LIST OF RESEARCH OUTPUT

1. “Phytoremediation of Chromium: Distribution  and  Speciation  of  Chromium  in  Typha  angustifolia  as  Heavy  Metal Accumulator”.

2. “Efektivitas Lahan Basah Buatan Tipe Subsurface Flow dengan Penambahan Bakteri dalam Pengolahan Limbah Air Asam Tambang”.

3. “Effect of Substrate Variation on Constructed Wetland System Effectiveness in Reducing Total Chromium Concentration in Water”. International Conference on Food, Ecological and Life Sciences. 15-16 June 2015. Bangkok, Thailand.

4. “Chromium Absorption and Accumulation by Typha angustifolia as Heavy Metal Accumulator”. International Conference on Biosciences (ICoBio). 5-7 August 2015. Bogor, Indonesia.


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