The outbreak of coronavirus diseases (COVID-19) receives much attention globally. On January 30, 2020, WHO has stated it was a global health emergency. The Indonesian Government requiring that all work from home and restricting access to activities outside the home. In the Bali Province, it has had a positive impact on the environment, especially for the amount of waste generation and emissions. The main objectives of this study were to analyse solid waste generation and to provide a review of issues in environmental impact during and before the pandemic of COVID-19 in Bali Province. LCA technique has been used extensively to evaluate the environmental performance of several municipal solid waste management technologies. An LCA study consists of four stages, such as goal and scope, life cycle inventory, life cycle impact analysis, and interpretation. The degraded organic carbon (DOC) value before the pandemic was 0.121 while after the pandemic the DOC reduced to 0.058. Moreover, methane and carbon dioxide production from waste generation per day was counted in this study. The total global warming potential from waste generation has been drastically reduced from 1,859.6 kg CO 2eq /day to 420.8 kg CO 2eq /day.

Microalgae has emerged as a promising approach for removing substrate and nutrient from wastewater with the concomitant biofuel production. The substrate and nutrient removal are influenced by several factors such as C/N ratio, F/M ratio, pH, and DO. This study aims to determine the efficiency of substrate and nutrient removal with the growth rates of microalgae and biomass by varying the addition of aeration and substrate. Intermittently aerated reactors were used with the flow rate of 14 L/minute. The batch reactors were prepared by adding glucose substrate of 50 mg/L (Ra0A), 100 mg/L (Ra0B), and 150 mg/L (Ra0C) without aeration; 50 mg/L (Ra12A), 100 mg/L (Ra12B), and 150 mg/L (Ra12C) with 12-hour aeration, and 50 mg/L (Ra24A), 100 mg/L (Ra24B), and 150 mg/L (Ra24C) with 24-hour aeration. The substrate removal, expressed as chemical oxygen demand (COD) in the reactor with aeration, showed the efficiency of 73.88% ± 2.05 (12-hour aeration), 75.2% ± 3.97 (24hours aeration), and 69.86% ± 5.69(without aeration). Nutrient removal as ammonia-N (NH3-N) gave high removal value of 98.3% ± 0.11 and the removal of nutrient as phosphate (PO3-4) showed the efficiency of 54.3% ± 0.1. The growth rate of microalgae and biomass exhibited the highest value in Ra24C reactor with the values ??of 0.0229/day and 0.1295/day, respectively. The pH values ??indicated a shift from normal to alkaline while DO values ??increased by the addition of 12 and 24-hour aeration.

Nitrogen and organic matter are part of the pollutant causing eutrophication in freshwater. Textiles industry like Endek is the main source of Nitrogen and organic matter. Tis paper aims to know the degradation process of Ammonia-Nitrogen (NH3-N) and Chemical Oxygen Demand (COD) with ozone pretreatment in operated by different DO level activated sludge. There are 2 scenarios of treatments in this study: with ozone pretreatment (R1) and without ozone pretreatment (R2). Wastewater treatment began with the seeding and acclimatization process. This acclimatization study showed the efficiency degradation of NH3-N and COD by 17.7 and 27.5 %. Biological Oxygen Demand (BOD)/COD level increased with ozone pretreatment, from 0.25 to 0.38, COD/TKN level stated at 3.26. Ozone pretreatment reduced NH3-N and COD by 23.8 and 34.1 %. Wastewater treatment with activated sludge operated by different DO levels showed efficiency of 44.2 % (R1) and 68.2 % (R2). This ammonia elimination was capable of preventing eutrophication in the waterbody. The efficiency of NH3-N and Nitrogen organic degradation was indicated by TKN (Total Kjeldahl Nitrogen) levels: 87 % (R1) and 79 % (R2). The concentration of Nitrate (NO3-N) increased from 2.9 to 5.5 mg/L when DO reached 1 - 3 mg/L. COD reduction levels in this study were 17 % (R1) and 42.5 % (R2). Ozone pretreatment could make the efficiency of wastewater treatment qualified into standard quality.

The purpose of this research is to investigate wastewater treatment with ozone pretreatment and post-treatment integrated with Moving Bed Biofilm Reactor (MBBR). Ozonation as a pre-treatment served to increase the Biochemical Oxygen Demand (BOD)/Chemical Oxygen Demand (COD) ratio while as a post-treatment to remove the remaining organic residues. Ozone doses were 1 mg/min, 4 mg/min, 20 mg/min, and 40 mg/min. In the pre-treatment, ozone produced a BOD/COD value of 0.68. The MBBR process had a COD and color removal efficiency of 68.89% and 67%, respectively. In the MBBR process without ozone pre-treatment, the efficiency of COD and color removal were 79.31% and 64.7%, respectively. The effluent treatment results from MBBR were then processed with ozone and showed the highest COD and color removal results of 76.8% and 99%, respectively. In this study, the processing with ozone as post-treatment was better than the pre-treatment.

Problems in municipal solid waste sector remains a challenge to solve for the government of Indonesia. Processing waste into fuel, or known as refuse derived fuel (RDF), are some of the technological alternatives considered to tackle the waste problem. This paper aims to describe recent information on municipal solid waste generation in major cities of Indonesia, including DKI Jakarta, Tangerang, Bekasi, Bandung, Semarang, Surakarta, Surabaya, Makassar, Denpasar, and Palembang, and to overview its potential for energy utilization as refuse derived fuel (RDF). Municipal solid waste generation in Indonesia was assessed based on sources, generation rate, and composition data by year of 2018. Data was obtained from the State Ministry of Environment and Forestry’s (SMEF) national inventory of waste generation website, the National Waste Information System (SIPSN). To assess refuse derived fuel (RDF) potential, waste characteristics such as calorific value, water content, volatile content, ash content is evaluated for each composition. In those cities, municipal solid waste generation rate was 0,69 kg/capita-day, with 1780 tonnes/day generated on an average per city. Household sector was significantly the largest source of municipal solid waste generation in all cities in Indonesia, which contributed 44-75% to total waste generated. The composition of municipal waste consists of 43.78% of food waste, 16.05% of paper, and 14.08% of plastics. The result of calculations showed that, mixed municipal solid waste from those cities has high water content with average of 49.94%, high volatile content with average of 53.34%, and low ash content with average of 6.12%. Calculated heating value of the mixed municipal solid waste is 9.5 MJ/kg which is lower than standard for refuse derived fuel of 12.56 MJ/kg. Therefore, sorting and pre-treatment mixed municipal solid waste in Indonesia is necessary to meet the criteria of refuse derived fuel material.