Conventional pump-and-treat strategies for dealing with groundwater contamination are both energy- and time-consuming. Potential passive biological techniques are of interest to remedy the massive volume of total petroleum hydrocarbon (TPH)-contaminated groundwater worldwide. In this study, novel biopellets made of TPH-acclimated microbes, fermented fruit peel materials, and CaO2 recycled from eggshells were manufactured to treat TPH-contaminated groundwater. The biopellets provided 56 mg of oxygen and achieved a C:N:P ratio by weight of 10:4:1. Moreover, each biopellet was capped with alginate to prolong its floating time in water to 25 days. The mimicked groundwater spiked with 500 mg/L diesel TPHs (TPHd) was treated using our novelly manufactured biopellets. After 8 days of treatment, results showed a 98.8% removal of spiked TPHd at a rate of 64.1 mg/L per day, with a microbial count that increased from nearly zero to 1.0 × 107 CFU/mL. The residual TPHd constituents were mainly C13–C18. Furthermore, microbial consumption of N, P, and oxygen was noted during the 8-day period of TPHd removal. As the TPHd level increased to 1500 mg/L, the removal rate reached 45 mg/L per day, and all TPHd had been removed after 22 days.
Nowadays, the structural complexity of dyes used in the textile industry and the widely adopted water-saving strategy in the dyeing processes often fail plants’ biological wastewater treatment units due to chemical oxygen demand (COD) overload. To alleviate this problems, this study investigated a regenerable adsorption–oxidation process to treat dyeing wastewater with COD around 10,000 mg/dm3 using a highly nano-pored activated carbon (AC) as a COD adsorbent, followed by its regeneration using hydrogen peroxide as an oxidizing reagent. In addition to studying AC’s COD adsorption and oxidation performance, its operational treatment conditions in terms of temperature and pH were assessed. The results firstly demonstrated that about 50–60% of the COD was consistently adsorbed during the repeated adsorption operation before reaching AC’s maximum adsorption capacity (qmax) of 0.165 g-COD/g-AC. The optimal pH and temperature during adsorption were 4.7 and 25 °C, respectively. Secondly, AC regeneration was accomplished by using an initial peroxide concentration of 2.5% (by wt %) and EDTA-Fe of 2.12 mmole/dm3. The reuse of the regenerated ACs was doable. Surprisingly, after the first AC regeneration, the COD adsorption capacity of the regenerated AC even increased by ~7% with respect to the virgin AC. Thirdly, the results of a five-consecutive adsorption–regeneration operation showed that a total of 0.3625 g COD was removed by the 5 g AC used, which was equivalent to an adsorption capacity (q) of 0.0725 (= 0.3625/5) g-COD/g-AC during each adsorption stage. Based on the obtained results, a regenerable COD adsorption–oxidation process using a nano-pored AC to treat the high-textile-COD wastewater looks promising. Thus, a conceptual treatment unit was proposed, and its potential benefits and limitations were addressed.
Some mosquitos are disease-causing vectors. Their widespread existence poses a great threat to disease control worldwide. Finding an effective, low-cost solution for mosquito population control is desperately needed. Pruned branches from three fruit trees of date, pomelo, and guava were chopped, dried, and smoldered to form biochar and smoke. The smoke was condensed at 6 °C to form a smoke condensed liquid (SCL) to be used as a larvicide for mosquito larva control. The SCL had a smoky smell, minimal nutrients, and little metal contents, yet contained plenty of phenolic molecules commonly used as biocides. Via bacterial inhibition zone tests, ten percent of the date, pomelo, and guava SCLs had 1.44, 1.13, and 0.83 times higher bactericidal effects, respectively, than the use of 75% ethanol. The effectiveness of bacterial inhibition was positively related to the amounts of volatile compounds in the SCL liquids. As for larvicidal effects, a ten percent solution of the date and pomelo SCLs killed all tested larvae within 2 hrs. The reactive time versus each SCL’s LC50 was determined and fitted with a first-order mathematic model. The adopted model and its estimated parameters showed satisfactory results in presenting the dose–effect relationships in larval mortality of all the tested SCLs. Finally, the liquid pHs and dissolved oxygen (DO) over time were examined for their effectiveness and variation, respectively, and the SCL addition was concluded as the sole key factor in the mortality of the tested larvae.
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