The high scientific standards maintained by H2Open Journal, in their papers owe much to the continuing dedication of the journals’ reviewers, who give freely of their time and expertise. IWA Publishing is pleased to pay tribute to this contribution by recognizing those who have participated in the review process. Thus, the Editor in Chief, Editors and Associate Editors acknowledge with particular gratitude the following reviewers who have reviewed papers during the period January 2019–December 2019.
| Aminuddin Ab Ghani | Manpreet Singh Bhatti | Andrei-Mugur Georgescu |
| Ali Abbasi | Lucia Bonadonna | Neil Grigg |
| Mansoor Ahammed | Adrian Bonilla-Petriciolet | Takashi Hashimoto |
| Marcos Airton de Sousa Freitas | Iacopo Borsi | Xiao Huang |
| Ryan Albert | Isabel Brás | Edevar Luvizotto Junior |
| Alla Aleksanyan | Isobel Brink | Sylvia Mudau |
| Catalina Alfaro de la Torre | Laura Bulgariu | Umamahesh Nanduri |
| Adel Al-Gheethi | Mario Cerroni | Tze Ling Ng |
| Edip Avsar | Ian Corbin | Manali Pal |
| Azadeh Babaee | Joseph Cotruvo | Miguel Angel Pardo Picazo |
| Vladan Babovic | Regulwar D G | Sonali Pattananayak |
| Chandan Banerjee | Katharine Dahm | Sandhya Rao Poleneni |
| Andrew Barton | Sruthi Dasika | K. Srinivasa Raju |
| Paul Baumgardner | Mawuli Dzakpasu | Adarsh S |
| Rolf Baur | Ibrahim El-Baroudy | Ken Thomas |
| Donald Begbie | FabrÃcio Ferrarini | |
| Laurence Bentley | Samuel Fosu Gyasi |