# Editorial on the Special Issue “Application of Environmentally Friendly Technologies in Green Processes”

Hayet Djelal

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Hayet Djelal. Editorial on the Special Issue “Application of Environmentally Friendly Technologies in Green Processes”. Processes, 2025, 13 (2), pp.318. 10.3390/pr13020318. hal-04912513

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Editorial

# Editorial on the Special Issue “Application of Environmentally Friendly Technologies in Green Processes”

Hayet Djelal ID

UniLaSalle Ecole des Métiers de l'Environnement, Cyclann, Campus de Ker Lann, Av. Robert Schuman, 35170 Bruz, France; hayet.djelal@unilasalle.fr; Tel.: +33-299058800

The treatment of wastewater by activated sludge, known as conventional biological treatment, is widely implemented. However, the removal efficiency is very low for biorecalcitrant compounds, such as dyes, drug residues, pesticides, and hydrocarbons, as well as heavy metals [1,2]. Furthermore, novel processes must be developed through a combination of treatments, for example, biological treatment combined with advanced oxidation processes [3], the use of green chemicals [4], and the management of by-products of treatment processes [5–7].

This Special Issue on "Application of Environmentally Friendly Technologies in Green Processes" aims to curate novel advances in the treatment of organic and inorganic micropollutants, with a view to preserving the natural environment. The valorization of treatment co-products is also addressed, for example, on sludge resulting from the biological treatment of wastewater. All articles in this Special Issue were selected after rigorous peer review. There is wide interdisciplinary collaboration with some international partnerships.

Three literature reviews offer an inventory of wastewater treatment techniques. The first concerns the treatment of dyes [8]; the second, slaughterhouse wastewater [9]; and the third, the treatment using UASB reactor technologies [10].

Three articles present innovative approaches based on green processes. In fact, Arabica coffee husk was used as a precursor for biochar preparation, which was then used in the Fenton-like process of Dicamba, an herbicide [11]. In other cases, the leaf extract of *Cascabela thevetia* enables the green synthesis of AgNO₃, which has antibacterial activity [12]. The third study concerns the elimination of heavy metals by adsorption on a biosorbent from *Monotheca buxifolia* seeds [13].

The topic of sludge from wastewater treatment is addressed through either production reduction or recovery. The amount of sludge in electrochemical machining can be reduced through complexing (with EDTA) or reducing (with ascorbic acid) processes. This sludge reduction significantly increases the lifespan of equipment and reduces the cost of the process [14]. Surplus sludge from sewage treatment plants was mixed with Portland cement for application in construction materials [15]. Another approach is to mix sludge with Sorel cement [16].

The last article applies an artificial neural network (ANN) to optimize the removal of several pollutants from aqueous solution, with the aim of optimizing returns [17].

It is expected that this Special Issue will significantly contribute to further research on wastewater treatment with green processes.

**Data Availability Statement:** Not applicable.

**Conflicts of Interest:** The author declares no conflicts of interest.

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Received: 6 January 2025

Revised: 14 January 2025

Accepted: 21 January 2025

Published: 24 January 2025

**Citation:** Djelal, H. Editorial on the Special Issue "Application of Environmentally Friendly Technologies in Green Processes". *Processes* **2025**, *13*, 318. https://doi.org/10.3390/pr13020318

**Copyright:** © 2025 by the author. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/).
## References

1. Gupta, S.; Mittal, Y.; Panja, R.; Prajapati, K.B.; Yadav, A.K. Conventional wastewater treatment technologies. In *Current Developments in Biotechnology and Bioengineering*; Elsevier: Amsterdam, The Netherlands, 2021; pp. 47–75. [CrossRef]

2. Dong, H.; Yuan, X.; Wang, W.; Qiang, Z. Occurrence and removal of antibiotics in ecological and conventional wastewater treatment processes: A field study. *J. Environ. Manag.* **2016**, *178*, 11–19. [CrossRef] [PubMed]

3. Aboudalle, A.; Djelal, H.; Domergue, L.; Fourcade, F.; Amrane, A. A novel system coupling an electro-Fenton process and an advanced biological process to remove a pharmaceutical compound, metronidazole. *J. Hazard. Mater.* **2021**, *415*, 125705. [CrossRef] [PubMed]

4. Cherif, S.; Rezzaz-Yazid, H.; Hemidouche, S.; Farsi, A.; Mostefaoui, S.; Belmedani, M.; Djelal, H.; Sadaoui, Z. Comparative study on the photocatalytic efficiency of ZnO nanoparticles synthesized via chemical and eco-friendly coprecipitation methods. *Ceram. Int.* **2025**, *51*, 4737–4749. [CrossRef]

5. Guo, J.S.; Fang, F.; Peng Yan, P.; Chen, Y.P. Sludge reduction based on microbial metabolism for sustainable wastewater treatment. *Bioresour. Technol.* **2020**, *297*, 122506. [CrossRef] [PubMed]

6. Changa, Z.; Longa, G.; Zhoua, J.L.; Cong, M. Valorization of sewage sludge in the fabrication of construction and building materials: A review. *Resour. Conserv. Recycl.* **2020**, *154*, 104606. [CrossRef]

7. Liua, H.; Basar, I.A.B.; Nzihou, A.; Eskicioglu, C. Hydrochar derived from municipal sludge through hydrothermal processing: A critical review on its formation, characterization, and valorization. *Water Res.* **2021**, *199*, 117186. [CrossRef] [PubMed]

8. Alsukaibi, A.K.D. Various Approaches for the Detoxification of Toxic Dyes in Wastewater. *Processes* **2022**, *10*, 1968. [CrossRef]

9. Ng, M.; Dalhatou, S.; Wilson, J.; Kamdem, B.P.; Temitope, M.B.; Paumo, H.K.; Djelal, H.; Assadi, A.A.; Nguyen-Tri, P.; Kane, A. Characterization of Slaughterhouse Wastewater and Development of Treatment Techniques: A Review. *Processes* **2022**, *10*, 1300. [CrossRef]

10. Sikosana, M.L.; Khoabane Sikhwivhilu, K.; Moutloali, R.; Madyira, D. Application of Pure and Modified Polyvinylidene Fluoride Materials for Wastewater Treatment Using UASB Reactor Technologies: A Review. *Processes* **2024**, *12*, 734. [CrossRef]

11. Guimarães, T.; Silva, E.M.G.d.; Aguiar, A.C.M.d.; Costa, M.M.d.; Mielke, K.C.; Mendes, K.F.; Silva, A.A.d.; Teixeira, A.P.d.C.; Moreira, R.P.L. Exploration of Eco-Friendly Hydrochar’s Potential in Advanced Oxidative Processes for Dicamba Degradation within Circular Bio-Economy Framework. *Processes* **2023**, *11*, 3244. [CrossRef]

12. Khan, A.N.; Ali Aldowairy, N.N.; Saad Alorfi, H.S.; Aslam, M.; Bawazir, W.A.; Hameed, A.; Soomro, M.T. Excellent Antimicrobial, Antioxidant, and Catalytic Activities of Medicinal Plant Aqueous Leaf Extract Derived Silver Nanoparticles. *Processes* **2022**, *10*, 1949. [CrossRef]

13. Khan, R.U.; Hamayun, M.; Altaf, A.A.; Kausar, S.; Razzaq, Z.; Javaid, T. Assessment and Removal of Heavy Metals and Other Ions from the Industrial Wastewater of Faisalabad, Pakistan. *Processes* **2022**, *10*, 2165. [CrossRef]

14. Cercal, G.; de Alvarenga, G.; Vidotti, M. Sludge Reduction and Surface Investigation in Electrochemical Machining by Complexing and Reducing Agents. *Processes* **2023**, *11*, 2186. [CrossRef]

15. Liang, J.; He, H.; Wei, J.; Han, T.; Wang, W.; Wang, L.; Han, J.; Zhang, L.; Zhang, Y.; Ma, H. Study of Solidifying Surplus Sludge as Building Material Using Ordinary Portland Cement. *Processes* **2022**, *10*, 2234. [CrossRef]

16. Ma, H.; Liang, J.; Wang, L.; He, H.; Wang, W.; Han, T.; Xu, Z.; Han, J. Mechanical Properties and Water Resistance of Magnesium Oxychloride Cement–Solidified Residual Sludge. *Processes* **2023**, *11*, 413. [CrossRef]

17. Zamouche, M.; Tahraoui, H.; Laggoun, Z.; Mechati, S.; Chemchmi, R.; Kanjal, M.I.; Amrane, A.; Hadadi, A.; Mouni, L. Optimization and Prediction of Stability of Emulsified Liquid Membrane (ELM): Artificial Neural Network. *Processes* **2023**, *11*, 364. [CrossRef]

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