The aim of this study is to evaluate the purifying ability of 3 parallel planted filters (PF1, PF2 and PF3) composed of three plants (Phragmites australis (Cav) Trin ex Steud, Typha latifolia L., Cyperus papyrus L.) on leachates from a landfill of industrial waste in Pointe-Noire (Republic of Congo). This landfill site includes a technical landfill for ordinary industrial waste (OIW) and a technical landfill for hazardous and soiled industrial waste (SIW). In order to assess purifying ability, we sampled 14 samples over 8 weeks, with 7 samples of the raw leachates from the technical landfill center, and 7 samples of leachates cleaned after passing through the tryptic vegetable filter. The physico-chemical analyzes made it possible to determine the following parameters: TOC, COD, NO3 -,PO42-, Ni, Cd, CrVI, Zn, Cu and Pb. The results showed a significant decrease in organic pollution with abatement rates in TOC and COD greater than 90%. The average removal efficiency is respectively 45.97% for nitrates and 40.2% for phosphates. The abatement rates for heavy metals range from 41.2% to 60.9% for nickel, from 52.2% to 68.5 % for cadmium, from 49% to 71.7% for chromium VI, from 59% to 74.6% for zinc, from 50.9 % to 65 % for copper and from 61.4% to 75.1% for lead. However, additional analyzes are needed to confirm the hypperaccumulator nature of these plant filters in particular absorption isotherms and kinetics of extraction of heavy metals of Phragmites australis (Cav) Trin ex Steud, Typha latifolia L., Cyperus papyrus L.)

Songolo River receives daily domestic and industrial wastewaters from households, laboratories, small and medium size industries (SMEs) and the Loandjili hospital, which are discharged directly into it without prior treatment. The objective of this study is to evaluate the physico- chemical quality of wastewaters discharged into the Songolo River at Pointe-Noire in Republic of Congo. To do this, 56 wastewater samples were taken. Physicochemical analyzes as temperature, pH, electronical conductivity, total dissolved solids, chloride ions, nitrate ions and total hydrocarbons, were      carried out on wastewaters. These analyzes showed that in terms of time, during wet periods (April to June), the values of the physico-chemical parameters (conductivity, total dissolved solids, chlorides ions, nitrates ions and total hydrocarbons) are the lowest due to the dilution phenomenon brought by the rains. On the other hand, the beginning of the dry season (July) is marked by much higher levels. The results of physico-chemical analyzes of these effluents also revealed that conductivity, total dissolved solids and total hydrocarbons often have values higher than those recommended by the WHO standard for wastewaters intended for release into the natural environment.

The aim of this study is to understand mechanisms that occur during leaching of alkali-resistant zirconium-containing glasses in acid and alkaline solutions. For this, we have developed 5 glass compositions: two alkali-resistant model glasses type CEMFIL, V1 (with zirconium and without heavy metals) and V2 (with zirconium and heavy metals), then three glasses of fly ashes V3 (without zirconium and with heavy metals), V4 (with 30 % of V3, zirconium and heavy metals) and V5 (with 60% of V3, zirconium and heavy metals). V4 and V5 are obtained using V3 as raw material and supplementing with SiO2, ZrO2 and Na2O to give them alkali-resistant properties. Glasses leaching in acidic and basic medium led to an important basification from the first times of alteration at pH = 4 when a basification decrease is observed for solutions initially at pH = 13. Normalized elementary mass losses results showed that, glass alteration  is higher for low-calcium glasses (V1 and V2) and V4 and V5 glasses have the lowest elemental mass losses at pH = 4 and 13. SIMS profiles made on glass alteration films permitted to observe behaviour of  H, Na, Ca, Si and Zr elements after  28 days at pH = 4 and 13 and understand the different  dissolution mechanisms involved. SIMS profiles showed that a hydrated film develops on glass surface characterized by hydrogen enrichment and sodium depletion irrespective of the glass. These glasses are also characterized by a surface enrichment of zirconium (except V3 which does not contain zirconium) whatever the pH. Hydrated film thickness confirm that V1, V2 and V3 glasses are more altered than V4 and V5 glasses. These results are confirmed by ICP-AES leachate analysis.

The brewing industry generates large amounts of wastewater which are released into surface water after treatment. The aim of this study is to evaluate the performance of the anaerobic treatment of brewery wastewaters in a UASB bioreactor containing activated sludge. After sixweeks operation, 30 samples were taken. Physicochemical analyzes were carried out on activated sludge (T, pH, VFA) and raw and treated waters (T, pH, AT, CAT, TSS, and COD). These analyzes showed that the conditions of the environment were favorable to an optimal growth of the bacteria: Mbemba et al.; IJECC, 9(7): 425-434, 2019; Article no.IJECC.2019.035 426 temperatures and pH were mostly mesophilic. the ionization of VFA was continuous and their concentration increased at the exit of the bioreactor thus revealing a significant conversion of organic materials by bacteria. The average values of the physicochemical parameters of the raw and treated wastewaters respectively increased from 31.5°C to 35°C for the temperature, from 8.9 to 7.5 for the pH, to 5.54 mg/l at 0 for AT, from 12.35 mg/l to 3.45 mg/l for TAC, from 234.08 mg/l to 129.61 mg/l for TSS and from 1637 mg/l to 282, 46 mg/l for COD. The effectiveness of the treatment allowed a COD reduction ranging from 70 to 94%. Original Research Article

Inadequate management of ash generated by household waste burned in open air in Republic of Congo, generates pollution sites especially through heavy metal contamination (Pb, Ni, Cr, Cu, Zn). The aim of this study is to evaluate the chemical durability of cementitious matrices containing waste ashes and their ability to retain in their structure heavy metals contained in these ashes. To do this, we collected 40 kg of waste coming from 4 landfills (A, B, C, D) in Brazzaville city. Waste was then burned and turned into ash. 6 cementitious matrice formulations (P1, P2, P3, P4, P5, P6) based on Dolisie Portland cement were made by varying the cement/ash/lime rations. We carried out static leaching tests with raw ashes and cementitious matrices at pH = 7 and at 25°C in distilled water during 30 days. This study shows that cementitious matrices containing ash have good potentiality for retention of heavy metals (more than 75%). But, cementitious matrices containing ash and lime give better results with retention rates between 90-99%.