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Implementation of outdoor photobioreactors has been challenged by an extremely oversaturated daily peak of solar irradiance. This study aims to understand the role of column size and paranet shading as well as to investigate the most convenient light control in outdoor cyanobacterial culture. The photobioreactor (PBR) consisted of plastic columns with a diameter of 12.74 cm (PBRd-20) and 31.85 cm (PBRd-50) laid outdoors and inclined at 158.22° upwards against solar radiation, while paranet shading was provided at 0%, 50%, 70%, and 90% shading capacity. A semi-continuous culture of cyanobacterium Arthrospira (Spirulina) platensis was conducted for 6 weeks with weekly monitoring of the growth parameter as well as the proximate and pigments content, while the daily irradiance and culture maximum temperature were recorded. The result shows that the column diameter of 12.74 cm had a lethal risk of 44.7% and this decreased to 10.5% by widening the column diameter to 31.85 cm. This lethal risk can be eliminated by the application of a paranet at a 50% reduction level for the column diameter of 31.85 cm and a 70% reduction level for the column diameter of 12.74 cm. The highest culture productivity of 149.03 mg/(L·day) was achieved with a PBRd-20 with 50% shading treatment, but a PBRd-50 with 90% shading treatment led to an increase in the protein and phycocyanin content by 66.7% and 14.91%, respectively.

This study aimed to examine the characteristics of HCWs infected with COVID-19 and factors associated with healthcare-associated infection. A cross-sectional study, using secondary data of COVID-19 HCW cases from a registry developed by the Occupational and Environmental Health Unit (OEHU) in Kedah State Health Department, Malaysia, was analysed using Excel and STATA version 14.0. Descriptive analysis and multiple logistic regression were conducted to identify the factors for healthcare-associated COVID-19 infection. A total of 1679 HCWs tested positive for COVID-19 between 1 January 2021 and 19 September 2021. The infection was mainly non-healthcare-associated (67.0%), with healthcare-associated cases contributing to only 33% of the cases. The significant factors associated with healthcare-associated transmission were the following: doctor (aOR = 1.433; 95% CI = 1.044, 1.968), hospital setting (aOR = 1.439; 95% CI = 1.080, 1.917), asymptomatic (aOR = 1.848; 95% CI = 1.604, 2.130), incompletely or not vaccinated (aOR = 1.400; 95% CI = 1.050, 1.866) and CT-value ≥ 30 (aOR = 2.494; 95% CI = 1.927, 3.226). Identifying factors of healthcare-associated infection would help in planning control measures preventing healthcare-associated transmission in the workplace. However, more than half of COVID-19 cases among HCWs involved non-healthcare-associated COVID-19 infection, and, thus, requires further study to identify high-risk behaviours.