Volume 20 - 2018

It is an indisputable fact that any environmental clean-up technology generating certain kind of effective result would be easily supported. One of them includes Permeable reactive bio-barrier which is an innovative technology started from 90’s to treat a variety of contaminants along the natural gradient flow of groundwater through immobilization or transformation of pollutants into less toxic and harmful form. Despite of any broad acknowledgement, there are lesser known knowledge about use of microorganisms in permeable reactive barriers, mingling of microorganisms with other reactive media and their effect on each other’s reactivity. The current review deals with an overview of the types of reactive media used in Permeable Reactive Barriers (PRBs) as well as different bio-barriers (PRBBs) utilized for the treatment of various contaminants, long–term performance of permeable reactive barrier and combination of microorganism and reactive media to look forward for their symbiotic relationship in permeable reactive barrier for environmental remediation.

In this study, raw boron enrichment waste was treated with hydrochloric acid and ultrasound at 35-kHz frequency for 60 minutes. To optimize the adsorption conditions for removal of methylene blue (MB) from synthetic wastewaters using raw boron enrichment waste (BEW), acid modified boron enrichment waste (HBEW) and ultrasound modified BEW (UBEW) by adsorption process and to compare the adsorption efficiency of chemical and ultrasonic modifications of BEW were aimed. The optimum adsorption conditions were determined economically and eco-friendly aspect and MB removal percents were found as 80%, 80% and 92% at optimum conditions for BEW, HBEW and UBEW, respectively. The maximum regression coefficient values were obtained as 0.911, 0.998 and 0.984 for BEW, HBEW and UBEW, respectively at Langmuir isotherm model. The adsorption rate was fitted well to pseudo-second order kinetics according to a good correlation coefficient. The adsorption of MB onto adsorbents studied is spontaneous in nature and feasible because of negative ∆G values. The results indicated that the boron enrichment process waste could be a suitable adsorbent for removal of MB from aqueous solution. The maximum adsorption capacities were equal to about 107,0 mg/g, 160,7 mg/g and 145,3 mg/g for BEW, HBEW and UBEW adsorbents at 298 K, respectively. The maximum dye removal percent was achieved for UBEW as 92% and ultrasound assisted modification was found more efficient method compared with acidic modification for MB removal.

The content of heavy metals in sediment and the aquatic plant Phragmites australis (roots and leaves), collected from six different stations along the Nil river, were determined providing information about heavy metals pollution status of this aquatic ecosystem.
The results showed that the abundance of heavy metals measured in the sediments decreased in the order: Fe>Zn>Pb>Cr>Cd. Apart from Cr and Fe, the concentration of heavy metals exceeded the background values. Metals concentrations were found decreasing with the increasing distance from the river mouth, suggesting that anthropogenic inputs, related to agricultural and domestic discharge into the river, are the major sources of heavy metals in the river sediments and aquatic plants.
The assessment of heavy metals pollution was carried out using geoaccumulation index (Igeo) and enrichment factor (EF). According to the mean values of Igeo, the sediment of Nil river is considered as moderately polluted with Pb and Cd, unpolluted to moderately polluted with Zn and unpolluted with Cr and Fe. The mean values of enrichment factor indicate that all stations presented moderate enrichment with Zn, minor enrichment with Cr and moderately to severe enrichment with pb and Cd in three stations.
Regarding the plant samples, the results showed that the concentration of the elements analyzed in Phragmites australis did not exceed the threshold of phytotoxicity.
Mean concentrations of all elements were less in the plants organs compared to the concentrations of the same elements in the corresponding sediment sample. Metals accumulated by P. australis were mostly distributed in root tissues, as shown by the values of translocation factors (TF) which were <1. A positive association between the metal concentrations in P. australis organs and its environment was also found; this suggests that this plant can be used as biological indicator in biomonitoring studies.

The paper presents a laboratory study of concrete mixes based on the alkali-activation of an industrial by-product, ground granulated blast furnace slag (GGBS). A number of factors potentially affecting the resulting concrete quality in terms of workability and strengths were investigated (namely activator type, molarity, curing conditions and times). The statistical significance of the effect of these factors was supported by ANOVA. Higher workability and strengths (with lower activator concentrations) were obtained for KOH containing mixes. Curing at constant moisture and ambient temperature was successful for most alkaline activators and mixes, which showed good concrete strengths at all curing times; when Na2SiO3 was used in addition to NaOH or KOH activators of moderate to high molarity, strengths exceeded those of Ordinary Portland Cement (CEM-I) concrete of a similar water/cement ratio.