Nazaitulshila Rasit

Seawater contamination with pathogenic bacteria, such as Vibrio parahaemolyticus (V. parahaemolyticus), remains a serious environmental concern in aquaculture and coastal communities. Conventional water treatment methods often fail to achieve efficient microbial inactivation, largely because resilient bacteria persist. This study synthesised a cerium oxide–zinc oxide (CeO2 –ZnO) heterostructured catalyst and evaluated its efficacy in the photocatalytic disinfection of V. parahaemolyticus under UV light irradiation. A full-factorial design was employed to optimise the disinfection process. The effects of three key variables, including UV irradiation time (15 minutes to 60 minutes), photocatalyst dosage (0.5 g/L to 2.0 g/L), and initial pH (6 to 9), on photocatalytic disinfection efficiency (%) were investigated. Analysis of variance (ANOVA) revealed that all three factors and their interactions have significant effects on the photocatalytic disinfection efficiency of the CeO2 –ZnO heterostructured catalyst. The optimal conditions for achieving maximum bacterial disinfection against V. parahaemolyticus (99.9% reduction in CFU) were identified at a photocatalyst dosage of 0.5 g/L, UV irradiation for 60 minutes and an initial pH of 6. The findings proved the potential of CeO2 –ZnO heterostructured catalyst as an effective alternative for sustainable water disinfection, particularly in aquaculture water treatment applications. The use of statistical optimisation ensures process efficiency and scalability

Anaerobic digestion is considered an environmentally friendly approach as it converts organic waste into valuable resources such as biogas and organic fertilizers while reducing solid waste. This study enhanced methane production from aquaculture sludge under different operating parameters: temperature (30 °C, 35 °C), S/I ratio (0.5, 1.0), and iron supplement concentration (6 g/L, 10 g/L). The biomethane potential test was conducted using full factorial design to evaluate the effects and interactions of these parameters on methane production. Copperas was utilized as an iron supplement in this study due to its cost-effectiveness and ability to reduce hydrogen sulfide formation, which can hinder microbial activity. Sample 1, which had a S/I ratio of 1.0, an iron supplement concentration of 10 g/L, and a temperature of 35 °C, had the maximum methane yield, with 22 ± 6 mL/g COD _removed . The ANOVA findings showed that the model was significant ( p < 0.05), with the S/I ratio ( A ) and iron supplement concentration ( B ) as significant main effects. The interaction effects between S/I ratio and iron concentration ( AB ), and between iron concentration and temperature ( BC ) were also significant. The R ² value of 0.9959 confirmed that the model fitted well with the experimental values. These findings emphasize the potential of copperas as a sustainable and effective iron supplement to improve methane production during anaerobic digestion while supporting the waste-to-energy concept. Graphical abstract

Sustainability in terms of the economy and the environment is severely hampered by poor waste management in the industrial sectors and a lack of renewable energy sources to meet expanding energy demands. To address this issue, the influences of sodium bicarbonate treatment on biogas generation during the anaerobic fermentation of corn stalks were analyzed. The application of sodium bicarbonate (9%, w/w) resulted in a significantly higher generation of 14692 mL biogas with a production of 223 mL/g, which was 30% higher than the untreated sample biogas generation. Surprisingly, chemical oxygen demand elimination was boosted by a factor of ten. In addition, sodium bicarbonate stabilized the pH of fermented corn stalks. The Gompertz modeling, according to the findings, had a significant correlation coefficient (> 0.995) and fit the accumulative biogas production trends well. Sludge recapture from the fermented effluent was 0.08 m3 sludge/m3 wastewater. Sodium bicarbonate added to corn stalks may increased the cumulative methane production while lowering chemical oxygen demand (COD) levels.

Anaerobic treatment of oily substrate, known as grease trap waste (GTW), was investigated for its practicability via continuous stirred tank reactor (CSTR) at different operating conditions and selected recovery strategies of feeding frequency efficacy. This study determine the performance of feeding frequency efficacy, namely feeding every 24 hours (R24H) and feeding every 12 hours (R12H). Under organic loading rate (OLR) of 2.2 gCOD/L.day, R12H exhibited methane composition of 57%, methane production rate of 0.27 LCH4/L.day, and methane yield of 0.14 LCH4/gCODremoved. At the same OLR, R24H recorded methane composition of 60%, methane production rate of 0.29 LCH4/L.day and similar methane yield as R12H. Findings indicated that R24H showed performance comparable to that of R12H. Given minor variation observed in performance, it is recommended that plant operators may consider scheduling two feedings per day for low loading conditions and switch to one feeding per day for higher loading conditions. This strategy is designed to balance the system and prevent shock loads, which could lead to plant shutdowns. This mechanism will induce their conversion to volatile fatty acids (VFAs); thus, reducing the risk of acid accumulation and pH drops, which could inhibit methanogens to produce methane, especially for oily substrate.

The rapid development of the aquaculture industry has contributed to the high amount of nutrients in wastewater that subsequently led to eutrophication and deterioration of water quality. Aquaculture wastewater consists of uneaten fish feed, fecal and other excretion or residue of chemicals used. Thus, this study aimed to evaluate the performance of hybrid coagulants of Moringa oleifera (MO) and copperas for aquaculture wastewater treatment. In this present study, different formulations of MO and copperas were explored in the coagulation treatment of aquaculture wastewater using a jar test experiment. The FTIR and SEM analysis are used to determine the morphology and surface of MO. This study focuses on the effect of coagulant aids formulation, coagulant dosage, the effect of initial pH and coagulation time on turbidity and ammonia removal in the coagulation of aquaculture wastewater. The finding shows that the highest removal of turbidity and ammonia was obtained with the use of 80% MO and 20% copperas at the condition of initial pH of 6 at 20 min of coagulation time, with the highest percentage removal of 66% and 91%, respectively. The coagulation isotherm of hybrid coagulant 80:20 is well described with the Freundlich isotherm model which describes the surface heterogeneity.

The potentials for non-stop hydrogen and methane production employing an ideal loading mixture of palm oil mill effluent (POME) and aquaculture wastewater (AWW) in a double-phase digester at a thermophilic state are presented. Different organic loadings were studied such as 31, 41, 51 and 61 Kg COD/(m3 d) for the generation of hydrogen; 9, 11, 14 and 16 kg COD/(m3 d) for the synthesis of methane. In a UASB reactor, hydrogen production was kept under control with a constant HRT of 12 h. At the loading of 51 kg COD/h, the maximal H2 content, volumetric H2 generation rate and H2 yield were observed as 46%, 6 L H2/d and 34 mL H2/g COD, respectively (m3 d). After an HRT of 6 days, the substrate from the hydrogen digester was further fermented into methane in the CSTR digester. At an organic loading rate of 14 kg COD/h, the highest volumetric CH4 generation rate and yield were 11 L CH4/d and 0.13 m3 CH4/kg COD, respectively (m3 d). This two-stage procedure removed 92% of the chemical oxygen requirement overall. Based on the findings, the Gompertz modeling was a good fit for the cumulative methane generation patterns, with a strong correlation coefficient (> 0.994). Sludge recovery was 0.07 m3 sludge/m3 wastewater and water recovery was 0.82 m3/m3 wastewater. This double-phase technique has the potential to contribute greatly to the development of a comprehensive waste management plan, including the digestion of palm oil mill effluent and aquaculture wastewater.

A unique dual-phase biological system for producing power from the potato wastes was developed. In the beginning, commercially available glucoamylase was used to hydrolyze potato wastes resulting the production of potato waste hydrolyzate. A 100 g of potato waste produced 30 g of hydrolysis solid and 750 mL of potato waste hydrolyzate. Within 6 h, the maximum glucose generation was 20 g/L while the maximum COD elimination was 85%. During the second phase, the soluble potato waste hydrolyzate was utilized to feed microbial fuel cells (MFC), which produced electricity. The maximum voltage measured was 1.1 V. When the external resistance was 1091 Ω, the power density reached its greatest point of 93 mW/m3. To evaluate MFC performance, a Coulombic efficiency of 20% was obtained, thus exploring a new field by converting the high-starch molecules into biofuels, thereby lowering the cost of commercial biofuel production.

This study looked into the possibility of using peroxydisulfate pretreatment to enhance biogas production from anaerobic fermentation of algal slurry. The results demonstrate that a peroxydisulfate added system with a dose of 0.02 g peroxydisulfate/g algal sludge TSS produces the most accumulative methane after 61 days of fermentation. At 0.02, 0.03, 0.06, 0.2, 0.3, 0.6, and 1.2 g peroxydisulfate/g algal sludge TSS cumulative methane generation was 1.16, 1.09, 1.15, 1.14, 1.09, 0.77, and 0.16 times higher than control. After 120 minutes of pre-treatment, the SCOD in the system continued to rise when the peroxydisulfate dosage was enhanced. To simulate the methane yield, a one-substrate model might be utilized. After dosing with peroxydisulfate, the hydrolysis rate reduced, and the maximum resultant and anticipated cumulative methane output was achieved with 0.02 g peroxydisulfate/g algal sludge TSS. After digestion, microcystin-LR in algae slurry was mostly eliminated. Heavy metals could be released from algae cells into the effluent as a result of the greater peroxydisulfate dosage. From the fermented effluent, sludge recapture was 0.09 m3 sludge/m3. The supplementation of peroxydisulfate to algae slurry may boost cumulative methane generation while also lowering microcystin-LR levels.