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Cooling towers are responsible for a large part of the industrial fresh water withdrawal, and the reuse of cooling tower water (CTW) effluents can strongly lower industrial fresh water footprints. CTW requires desalination prior to being reused, but various CTW components, such as total organic carbon (TOC), conditioning chemicals and total suspended solids (TSS) hamper physico-chemical desalination technologies and need to be removed from the CTW. A cost-efficient and robust pre-treatment is thus required, which can be provided by constructed wetlands (CWs). The present study is the first study that determined the CTW pre-treatment efficiency of hybrid-CWs and the impact of winter season and biocides in the CTW on the pre-treatment efficiency. The most efficient CW flow type and dominant removal mechanisms for CW components hampering physico-chemical desalination were determined. Subsurface flow CWs removed PO43−, TSS and TOC as a result of adsorption and filtration. Vertical subsurface flow CWs (VSSF-CW) excelled in the removal of benzotriazole as a result of aerobic biodegradation. Horizontal subsurface flow CWs (HSSF-CW) allowed the denitrification of NO3− due to their anaerobic conditions. Open water CWs (OW-CWs) did not contribute to the removal of components that hamper physico-chemical desalination technologies, but do provide water storage options and habitat. The biological removal processes in the different CW flow types were negatively impacted by the winter season, but were not impacted by concentrations of the biocides glutaraldehyde and DBNPA that are relevant in practice.For optimal pre-treatment, a hybrid-CW, consisting of an initial VSSF-CW followed by an OW-CW and HSSF-CW is recommended. Future research should focus on integrating the hybrid-CW with a desalination technology, e.g. reverse osmosis, electrodialysis or capacitive ionization, to produce water that meets the requirements for use as cooling water and allow the reuse of CTW in the cooling tower itself.

The current situation on fossil fuel reserves decline has an impact on the increasing demand for renewable energy usage. In developing countries, such as Indonesia, biogas as one of the potential renewable energy sources has positively responded by Indonesian society. However, despite the high biogas demand, biogas consumption pattern in Indonesia is rarely reported in the literature. The biogas consumption pattern is an essential aspect, which can be used as a parameter to improve biodigester performance. This study aims to close the knowledge gap of biogas consumption pattern by studying biogas usage variation in the community biogas plant in Sumedang, Indonesia, as a case study. This study used a literature review and questionnaire as its methodological approach, involving 60 respondents of biogas users. The results showed that the biogas equivalent amount to LPG consumption was 0.669 m3 per household per day or 0.17 m3 per person per day. Meanwhile, the net biogas consumption was 1.92 m3 per household per day or 0.49 m3 per person per day, higher than the reported values in the literature. The inefficiency of biogas stove (34.92% efficiency) was suspected to be the cause of high daily biogas consumption rate. It was also found that 82% (49) of biogas users used biogas in the range of 1 – 2 hours per day. The weekly biogas consumption pattern was found to be constant. Meanwhile, on a daily usage, a variation was found where the daily peak usage time occurred in the morning. Furthermore, this study also addresses the importance of having an efficient biogas stove for optimal biogas utilization.