Enriched sewage sludge from anaerobic pre-treatment in spurring valorization potential of black soldier fly larvae.

The valorization of sewage sludge by black soldier fly larvae (BSFL) has gained attentions for sewage sludge management since the sludge can be reduced securely as well as larval biomass can be used for biorefineries application. Nevertheless, the BSFL growth was impeded while assimilating nutrition from sewage sludge due to the presence of extracellular polymeric substances (EPS) that had entrapped the essential nutrients inside. Accordingly, the pre-treatment of sewage sludge via anaerobic digestion at different pH was employed in this work to rupture the EPS structure and release more nutrients for larval growth. The results showed that larvae fed with raw sewage sludge had attained the lowest final larval weight (2.05 ± 0.38 mg/larva) as opposed to batches fed with pre-treated sewage sludges. This was because the soluble carbohydrate (more than 6.81 ± 1.31 mg of glucose/g sewage sludge) in EPS was released after anaerobic pre-treatment, facilitating larval assimilation for growth. Furthermore, it was observed that further increasing of pH for sewage sludge pre-treatment had led to lower final larval weight gained due to the inhibitory effect stemming from ammonia production at higher pH. The anaerobic pre-treatment of sewage sludge being executed at pH 3 for 8 days had achieved the highest final larval weight at 7.34 ± 0.97 mg/larva. The still low quality of sewage sludges after the pre-treatment also offered benefit, where high sewage sludge reduction and waste reduction index were recorded due to the necessity of BSFL to consume more sewage sludge in compensating the nutrients destitution in sludge. Lastly, the possibility of predicting final larval weight was successfully materialized via a statistical model derived from the multiple linear regression method. The derived model incorporated the interactive parameters of anaerobic pre-treated pH and durations at various combinations could predict the final larval weight.

Residual palm kernel expeller as the support material and alimentation provider in enhancing attached microalgal growth for quality biodiesel production.

Albeit the biodiesel production from suspended microalgal system has gained immense interests in recent years, the domineering limitation of being economically infeasible has hindered this technology from partaking into a large-scale operation. To curtail this issue, attached growth system had been introduced by various studies; however, those were still unable to alleviate the socio-economic challenges faced in commercializing the microalgal biomass production. Thus, this study had developed a novel approach in cultivating-cum-harvesting attached Chlorella vulgaris sp. microalgae, whilst using solid organic waste of palm kernel expeller (PKE) as the supporting and alimentation material for microalgal biofilm formation. The effects of three variables, namely, PKE dosage, light intensity, and photoperiod, were initially modelled and later optimized using Response Surface Methodology tool. The derived statistical models could predict the growth performances of attached microalgal biomass and lipid productivity. The optimum growing condition was attained at PKE dosage of 5.67 g/L, light intensity of 197 µmol/m2 s and photoperiod of 8 light and 16 dark hours/cycle, achieving the microalgal density and lipid content of 9.87 ± 0.05 g/g and 3.39 ± 0.28 g/g, respectively, with lipid productivity of 29.6 mg/L day. This optimum condition had led to the intensification of biodiesel quality with a high percentage of monounsaturated fatty acid, i.e., oleic acid (C18:1), encompassing 81.86% of total fatty acid methyl ester components. Given that the positive acquisition of PKE as an excellent supporting material in enhancing the microalgal density and lipid productivity that had resulted in the commercially viable biodiesel quality, this study served as a novel revolution in augmenting the microalgae and solid waste utilities for sustainable energy generation.

Development of ß-cyclodextrin crosslinked citric acid encapsulated in polypropylene membrane protected-µ-solid-phase extraction device for enhancing the separation and preconcentration of endocrine disruptor compounds.

Endocrine disruptor compounds (EDCs) such as plasticisers, surfactants, pharmaceutical products, personal care products and pesticides are frequently released into the environmental waters. Therefore, a sensitive and environmentally friendly method is entailed to quantify these compounds at their trace level concentrations. This study encapsulated the ß-cyclodextrin crosslinked with citric acid in a polypropylene membrane protected-µ-solid phase extraction (BCD-CA µ-SPE) device for preconcentrating the EDCs (triclosan, triclocarban, 2-phenylphenol, 4-tert-octylphenols and bisphenol A) in real water samples before the analysis by high-performance liquid chromatography. FT-IR and TGA results indicated that BCD-CA was successfully synthesised with the formation of ester linkage (1078.33 cm-1) and O-H stretching from carboxylic acid (3434.70 cm-1) with higher thermal stability as compared with native CD with the remaining weight above 72.1% at 500 °C. Several critical parameters such as the sorbent loading, type and amount of salts, extraction time, sample volume, sample pH, type and volume of desorption solvents and desorption time were sequentially optimised and statistically validated. Under the optimum condition, the use of BCD-CA µ-SPE device had manifested good linearity (0.5-500 µg L-1) with the determination of the coefficient range of 0.9807-0.9979. The p-values for the F-test and t-test (6.60 × 10-8 - 1.77 × 10-5) were lesser than 0.05 and low detection limits ranging from 0.27 to 0.84 µg L-1 for all studied EDCs. The developed technique was also successfully applied for EDC analyses in four distinct real water samples, namely, wastewater, river water, tap water and mineral water, with good EDCs recoveries (80.2%-99.9%), low relative standard deviations (0.1%-3.8%, n = 3) with enrichment factor ranging from 9 to 82 folds. These results signified the potential of the BCD-CA µ-SPE device as an efficient, sensitive, and environmentally friendly approach for analyzing EDCs.

Fungal Fermented Palm Kernel Expeller as Feed for Black Soldier Fly Larvae in Producing Protein and Biodiesel.

Being the second-largest country in the production of palm oil, Malaysia has a massive amount of palm kernel expeller (PKE) leftover. For that purpose, black soldier fly larvae (BSFL) are thus employed in this study to valorize the PKE waste. More specifically, this work elucidated the effects of the pre-fermentation of PKE via different amounts of Rhizopus oligosporus to enhance PKE palatability for the feeding of BSFL. The results showed that fermentation successfully enriched the raw PKE and thus contributed to the better growth of BSFL. BSFL grew to be 34% heavier at the optimum inoculum volume of 0.5 mL/10 g dry weight of PKE as compared to the control. Meanwhile, excessive fungal inoculum induced competition between BSFL and R. oligosporus, resulting in a reduction in BSFL weight. Under optimum feeding conditions, BSFL also registered the highest lipid yield (24.7%) and protein yield (44.5%). The biodiesel derived from BSFL lipid had also shown good compliance with the European biodiesel standard EN 14214. The high saturated fatty acid methyl esters (FAMEs) content (C12:0, C14:0, C16:0) in derived biodiesel made it highly oxidatively stable. Lastly, the superior degradation rate of PKE executed by BSFL further underpinned the sustainable conversion process in attaining valuable larval bioproducts.

Correlating black soldier fly larvae growths with soluble nutrients derived from thermally pre-treated waste activated sludge.

Black soldier fly larvae (BSFL) have been deployed to valorize various organic wastes. Nonetheless, its growth rate whilst being offered with waste activated sludge (WAS) is not promising, likely by virtue of the presence of extracellular polymeric substances' structure in WAS. In this work, the WAS were first thermally pre-treated under different treatment temperatures and durations before being administered as the feeding substrates for BSFL. The results showed the thermal pre-treatment could improve WAS palatability and subsequently, enhance the growth of BSFL especially after the pre-treatments at 75 °C and above. The highest larva weight gained was recorded at 2.16 mg/larva for the WAS sample being pre-treated at 90 °C and 16 h. Furthermore, the samples pre-treated above 75 °C also achieved higher degradation rates, indicating that the 75 °C was a threshold temperature to effectively hydrolyze the WAS. The changes of WAS characteristics, namely, (i) soluble chemical oxygen demand (SCOD), (ii) soluble carbohydrate, (iii) soluble protein, (iv) humic substances and (v) total soluble protein and humic substances, after the thermal pre-treatments were also studied in correlating with the BSFL growth. Accordingly, a model was successfully developed with the highest R2 value attained at 0.95, evidencing the SCOD was the most suitable WAS characteristic to accurately predict the BSFL growth behavior.

Hydrolysis kinetics for solubilizing waste activated sludge at low temperature thermal treatment derived from multivariate non-linear model.

Low temperature thermal pre-treatment is a low-cost method to break down the structure of extracellular polymeric substances in waste activated sludge (WAS) while improving the sludge biodegradability. However, previous models on low temperature thermal pre-treatment did not adequately elucidate the behaviour of sludge hydrolysis process for the duration ranging from 5 to 9 h. Therefore, this work had developed an inclusive functional model to describe the kinetics of sludge hydrolysis for a wide range of treatment conditions (30 °C-90 °C within 0 and 16 h). As compared with treatment duration, the treatment temperature played a greater impact in solubilizing WAS. Accordingly, the 90 °C treatment had consistently produced WAS with the highest degree of solubility. Nonetheless, the mediocre discrepancies between 90 °C and 75 °C may challenge the practicality of increasing the treatment temperatures beyond 75 °C. The effects of treatment duration on soluble chemical oxygen demand, soluble carbohydrate and soluble protein were only significant during the first 4 h, except for humic substances release that continued to increase with treatment duration. Finally, a good fit with R2 > 0.95 was achieved using an inclusive multivariate non-linear model, substantiating the functionality to predict the kinetics of sludge hydrolysis at arbitrary treatment conditions.

A review on recent disposal of hazardous sewage sludge via anaerobic digestion and novel composting.

The high investment cost required by modern treatment technologies of hazardous sewage sludge such as incineration and anaerobic digestion have discouraged their application by many developing countries. Hence, this review elucidates the status, performances and limitations of two low-cost methods for biological treatment of hazardous sewage sludge, employing vermicomposting and black soldier fly larvae (BSFL). Their performances in terms of carbon recovery, nitrogen recovery, mass reduction, pathogen destruction and heavy metal stabilization were assessed alongside with the mature anaerobic digestion method. It was revealed that vermicomposting and BSFL were on par with anaerobic digestion for carbon recovery, nitrogen recovery and mass reduction. Thermophilic anaerobic digestion was found superior in pathogen destruction because of its high operational temperature. Anaerobic digestion also had proven its ability to stabilize heavy metals, but no conclusive finding could confirm similar application from vermicomposting or BSFL treatment. However, the addition of co-substrates or biochar during vermicomposting or BSFL treatment may show synergistic effects in stabilizing heavy metals as demonstrated by anaerobic digestion. Moreover, vermicomposting and BSFL valorization had manifested their potentialities as the low-cost alternatives for treating hazardous sewage sludge, whilst producing value-added feedstock for biochemical industries.

Systematic Performance Comparison of Fe3+/Fe0/Peroxymonosulfate and Fe3+/Fe0/Peroxydisulfate Systems for Organics Removal.

Activated zero-valent iron (Ac-ZVI) coupled with Fe3+ was employed to activate peroxymonosulfate (PMS) and peroxydisulfate (PDS) for acid orange 7 (AO7) removal. Fe3+ was used to promote Fe2+ liberation from Ac-ZVI as an active species for reactive oxygen species (ROS) generation. The factors affecting AO7 degradation, namely, the Ac-ZVI:Fe3+ ratio, PMS/PDS dosage, and pH, were compared. In both PMS and PDS systems, the AO7 degradation rate increased gradually with increasing Fe3+ concentration at fixed Ac-ZVI loading due to the Fe3+-promoted liberation of Fe2+ from Ac-ZVI. The AO7 degradation rate increased with increasing PMS/PDS dosage due to the greater amount of ROS generated. The degradation rate in the PDS system decreased while the degradation rate in the PMS system increased with increasing pH due to the difference in the PDS and PMS activation mechanisms. On the basis of the radical scavenging study, sulfate radical was identified as the dominant ROS in both systems. The physicochemical properties of pristine and used Ac-ZVI were characterized, indicating that the used Ac-ZVI had an increased BET specific surface area due to the formation of Fe2O3 nanoparticles during PMS/PDS activation. Nevertheless, both systems displayed good reusability and stability for at least three cycles, indicating that the systems are promising for pollutant removal.

Characterization and Kinetic Studies of Poly(vinylidene fluoride-co-hexafluoropropylene) Polymer Inclusion Membrane for the Malachite Green Extraction.

Textile industry effluent contains a high amount of toxic colorants. These dyes are carcinogenic and threats to the environment and living beings. In this study, poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-co-HFP) was used as the based polymer for PIMs with bis-(2-ethylhexyl) phosphate (B2EHP) and dioctyl phthalate (DOP) as the carrier and plasticizer. The fabricated PIMs were employed to extract the cation dye (Malachite Green; MG) from the feeding phase. PIMs were also characterized by scanning electron microscopy (SEM), atomic force microscope (AFM), contact angle, water uptake, Fourier-transform infrared spectroscopy (FTIR) and ions exchange capacity. The performance of the PIMs was investigated under various conditions such as percentage of carrier and initial dye concentration. With permeability and flux values of 0.1188 cm/min and 1.1913 mg cm/min, PIM produced with 18% w/w PVDF-co-HFP, 21% w/w B2EHP, 1% w/w DOP and 40% w/w THF and was able to achieve more than 97% of MG extraction. The experimental data were then fitted with a pseudo-second-order (PSO) model, and the calculated R2 value was ~0.99. This shows that the data has a good fit with the PSO model. PIM is a potential alternative technology in textile industry effluent treatment; however, the right formulation is crucial for developing a highly efficient membrane.

Stabilization of heavy metals loaded sewage sludge: Reviewing conventional to state-of-the-art thermal treatments in achieving energy sustainability.

Sewage sludge has long been regarded as a hazardous waste by virtue of the loaded heavy metals and pathogens. Recently, more advanced technologies are introduced to make use of the nutrients from this hazardous sludge. Successful recovery of sludge's carbon content could significantly convert waste to energy and promote energy sustainability. Meanwhile, the recovery of nitrogen and trace minerals allows the production of fertilizers. This review is elucidating the performances of modern thermal treatment technologies in recovering resources from sewage sludge while reducing its environmental impacts. Exhaustive investigations show that most modern technologies are capable of recovering sludge's carbon content for energy generation. Concurrently, the technologies could as well stabilize heavy metals, destroy harmful pathogens, and reduce the volume of sludge to minimize the environmental impacts. Nevertheless, the high initial investment cost still poses a huge hurdle for many developing countries. Since the initial investment cost is inevitable, the future works should focus on improving the profit margin of thermal technologies; so that it would be more financially attractive. This can be done through process optimization, improved process design as well as the use of suitable co-substrates, additives, and catalyst as propounded in the review.