Malaysia encounters a consistent rise in the generation of solid waste and leachate on a daily basis. It should also be noted that leachate has a low degree of biodegradability (BOD5 /chemical oxygen demand [COD]), as shown by its BOD5 /COD ratio. Its high toxicity levels significantly threaten the environment, water bodies, and human well-being. High concentrations of COD, color, and ammoniacal nitrogen (NH3 -N) in leachate prevent this wastewater from being allowed to be discharged directly into the water body. Therefore, an effective process to remove the pollutant is desired. The aims of this study are to investigate the performance of ozonation with two metallic compounds, ZrCl4 and SnCl4 , and optimize their performance using response surface methodology (RSM). In this study, the performance of ozonation with ZrCl4 (O3 /ZrCl4 ) recorded better pollutant removals compared with the ozonation with tin tetrachloride (O3 /SnCl4 ), as seen in the removals of 99.8%, 93.5%, and 46.3% for color, COD, and NH3 -N, respectively. These removals were achieved by following the experimental model (optimum experiment condition) generated by RSM at O3 dosage of 31 g/m3 , COD and ZrCl4 dosage ratio (COD, mg/L/ZrCl4 , mg/L) of 1:1.35, with the pH solution of 8.78 and reaction time of 89 min. The R2 of each parameter for this model was recorded as 0.999 (COD), 0.999 (color), and 0.998 (NH3 -N), respectively. These data indicated that the model is well fitted as the predicted data by statistical calculation and in good agreement with the actual data. PRACTITIONER POINTS: The performance of O3 /ZrCl4 and O3 /SnCl4 was examined for remediate stabilized landfill leachate. The performance of O3 /ZrCl4 and O3 /SnCl4 was optimized using RSM, and a set of experimental models was generated and tested. O3 /ZrCl4 recorded the higher removal of COD, color, and NH3 -N compared with O3 /SnCl4 . At best condition, both methods recorded removal as 89% to 99.8% of pollutants in leachate and product clear effluent. This finding gives a new approach to treat landfill leachate effectively and efficiently.
Studies have indicated that up to 47% of total N fertilizer applied in flooded rice fields may be lost to the atmosphere through NH3 volatilization. The volatilized NH3 represents monetary loss and contributes to increase in formation of PM2.5 in the atmosphere, eutrophication in surface water, and degrades water and soil quality. The NH3 is also a precursor to N2O formation. Thus, it is important to monitor NH3 volatilization from fertilized and flooded rice fields. Commercially available samplers offer ease of transportation and installation, and thus, may be considered as NH3 absorbents for the static chamber method. Hence, the objective of this study is to investigate the use of a commercially available NH3 sampler/absorbent (i.e., Ogawa® passive sampler) for implementation in a static chamber. In this study, forty closed static chambers were used to study two factors (i.e., trapping methods, exposure duration) arranged in a Randomized Complete Block Design. The three trapping methods are standard boric acid solution, Ogawa® passive sampler with acid-coated pads and exposed coated pads without casing. The exposure durations are 1 and 4 h. Results suggest that different levels of absorbed NH3 was obtained for each of the trapping methods. Highest level of NH3 was trapped by the standard boric acid solution, followed by the exposed acid-coated pads without casing, and finally acid-coated pads with protective casing, given the same exposure duration. The differences in absorbed NH3 under same conditions does not warrant direct comparison across the different trapping methods. Any three trapping methods can be used for conducting studies to compare multi-treatments using the static chamber method, provided the same trapping method is applied for all chambers.