Heavy metals and nutrients removal in a batch-fed greywater treatment system planted with Canna indica and Oryza sativa L.

The objective of this investigation was to determine whether Canna indica and Oryza sativa L. plants have the phytoremediation potential for removing heavy metals and nutrients from greywater treated in batch-fed Horizontal sub-surface Flow Constructed Wetlands (HssFCW). The HssFCW had a Hydraulic Retention Time (HRT) and organic loading rate (OLR) of 3 days and 3.96 (g.BOD/m2.day) respectively. Greywater (GW) samples were characterized for electrical conductivity (EC), total nitrogen (TN), total phosphorous (TP), pH, sodium adsorption ratio (SAR), metals (Al, Fe, Mg, Ca) and Biochemical Oxygen Demand (BOD5). The accumulation of metals in the soil and edible parts of plants was evaluated in terms of bioconcentration and translocation factors. Metal concentrations were determined using an atomic absorption spectrometer, while nutrients were by colorimetric method. The result shows that the metals and nutrients were below the WHO allowable limit for treated greywater recycling in agriculture. Nutrient removal was insignificantly different while metal removal was significantly different in the constructed wetlands (CW). The results indicated that C. indica is preferred as a perennial plant with unlimited metal accumulation and high nutrient removals compare to O. sativa L. with a high metal concentration in the above-ground plant tissue and also an annual plant.

Comparison of heavy metal and nutrients removal in Canna indica and Oryza sativa L. based constructed wetlands for piggery effluent treatment in north-central Nigeria.

Batch-fed horizontal sub-surface flow constructed wetlands (HssFCW) were developed to compare the potential of Canna indica and Oryza sativa L. in removing heavy metals and nutrients from piggery effluent. Piggery effluent samples were characterized for nutrients (N and P) and metals (Mg, Al, Ca and Fe) before and after introducing them to the HssFCW with hydraulic retention time (HRT) of 3 days and operational flowrate of 0.014 m3/day. Three sets of constructed wetlands (CWs) were monitored during the dry season for 3 months. The bioconcentration factor (BCF) and translocation factor (TF) for the plants were evaluated. The results were all significantly different at p ≤ 0.05. O. sativa L removes more nutrients and metals than C. indica. The BCF for O. sativa L. was higher than for C. indica, while the TF for C. indica was higher for O. sativa L., indicating a higher metal translocation potential. Use of C. indica, a non-food crop, poses no health risks in HssFCWs whereas the grains of O. sativa L. are consumed directly by humans, presenting potential risks when used in HssFCWs. Compared to an annual O. sativa L., the perennial C. indica can be grown continuously in CWs for the phytoremediation of piggery effluent. Novelty statementNo known work about the phytoremediation potential of the two studied macrophytes in the agro-ecological zone is known. The study also provides insight into the bioconcentration of metals in the edible part of Oryza sativa L. FARO 44 (SIPI 692033).The characterization of piggery effluent revealed that its compositions were above the allowable limit for reuse and recycling despite the adoption of low-water use intensive method.The study showed that Oryza sativa L accumulates more metals in the above-ground tissues than in its root and provide insight into its use as a phytoremediation plant in the study area.The footprint of pollutants and metals in Oryza sativa L makes a perennial C. indica more suitable than O. sativa L. in piggery effluent phytoremediation.

Phytoremediation of domestic wastewaters in free water surface constructed wetlands using Azolla pinnata.

Two constructed wetlands, one with Azolla pinnata plant (CW1) and the other without (CW2) for treating domestic wastewaters were developed. Fifteen water parameters which include: Dissolved Oxygen (DO), Biochemical Oxygen Demand (BOD5), Chemical Oxygen Demand (COD), Total Suspended Solid (TSS), Total Phosphorus (TP), Total Nitrogen (TN), Ammoniacal Nitrogen (NH3N), Turbidity, pH, Electrical Conductivity (EC), Iron (Fe), Magnesium (Mg), Manganese (Mn), and heavy metals such as Lead (Pb) and Zinc (Zn) were analyzed using standard laboratory procedures. The experiments were conducted in two (dry and wet) seasons simultaneously. Results showed considerable reductions in all parameters and metals including Zn in CW1 compared with CW2 in the two seasons considered while Pb and Mn were not detected throughout the study. Zn concentration levels reduced significantly in both seasons just as removal efficiencies of 70.03% and 64.51% were recorded for CW1 while 35.17% and 33.45% were recorded for CW2 in both seasons. There were no significant differences in the removal efficiencies of Fe in both seasons as 99.55%, 59.09%, 88.89%, and 53.56% were recorded in CW1 and CW2 respectively. Azolla pinnata has proved effective in domestic wastewater phytoremediation studies.

Landfill leachate treatment using sub-surface flow constructed wetland by Cyperus haspan.

Performance evaluation of pilot scale sub-surface constructed wetlands was carried out in treating leachate from Pulau Burung Sanitary Landfill (PBSL). The constructed wetland was planted with Cyperus haspan with sand and gravel used as substrate media. The experiment was operated for three weeks retention time and during the experimentation, the influent and effluent samples were tested for its pH, turbidity, color, total suspended solid (TSS), chemical oxygen demand (COD), biochemical oxygen demand (BOD(5)), ammonia nitrogen (NH(3)-N), Total phosphorus (TP), total nitrogen (TN) and also for heavy metals such as iron (Fe), magnesium (Mg), manganese (Mn) and zinc (Zn) concentrations. The results showed that the constructed wetlands with C. haspan were capable of removing 7.2-12.4% of pH, 39.3-86.6% of turbidity, 63.5-86.6% of color, 59.7-98.8% of TSS, 39.2-91.8% of COD, 60.8-78.7% of BOD(5), 29.8-53.8% of NH(3)-N, 59.8-99.7% of TP, 33.8-67.0% of TN, 34.9-59.0% of Fe, 29.0-75.0% of Mg, 51.2-70.5% of Mn, and 75.9-89.4% of Zn. The significance of removal was manifested in the quality of the effluent obtained at the end of the study. High removal efficiencies in the study proved that leachate could be treated effectively using subsurface constructed wetlands with C. haspan plant.

Solid waste generation and decomposition using compost bin technique in Pulau Pinang, Malaysia.

Solid waste comprised of a grass clippings mixture was decomposed using a locally-made compost bin in Pulau Pinang, Malaysia, to eliminate challenges associated with improper waste disposal. Bulk density, pH, moisture content, nutrients content, nitrogen (N), phosphorus (P), potassium (K), iron (Fe), zinc (Zn), copper (Cu) and carbon/nitrogen (C/N) ratio were determined over 77 days. A 34% reduction in compost bin volume was observed and bulk density and pH were also reduced from 732 to 482 kg m(-3) and 7.82 to 8.41, respectively, indicating fairly good performance. The final moisture content and C/N ratio were 44.06% and 14 : 1, respectively, and the results also showed that the presence of nutrients and heavy metals in the final compost were within acceptable limits for use as a soil conditioner. Final concentrations of N, P and K were 347 mg kg(-1), 510 mg kg(-1) and 14.8 g kg(-1) and for heavy metals, Fe, Zn and Cu were 5308, 300 and 20 mg kg(-1), respectively, which considerably assisted in the decomposition process. Processed waste materials from the bin were shown to be excellent organic fertilizers with over 75% germination index for seeds grown into bean sprouts in 72 h. An improved bin design to eliminate greenhouse gas emission into the environment is suggested.