2025 Volume 16 Issue 1 Pages 49-56
Cambodia exported more than 163,400 tons of fresh mangoes and 18,490 tons of processed, dried mangoes in 2022., Approximately 250–300 tons of dried mango are processed daily throughout the country. Mango processing produces wastewater which is a major concern and requires proper handling and treatment. This study aimed to assess the utilization of a lagoon digester on the mango processing wastewater including (1) ascertain the physio-chemical characteristics of mango processing wastewater; (2) estimate the biogas production and its quality; and (3) determine the potential greenhouse gas emission reductions available through this technology. The lagoon digester had a volume of 6,000 m3. The study was carried out from July to November2023, at a mango processing factory located in the Kampong Speu province in Cambodia. The factory produced up to 300 m3 of wastewater per day, which was diverted to the lagoon and then treated with NaOH and powdered calcium carbonate to raise the pH before feedstock was released into the lagoon pond. Three wastewater samples were obtained from the discharge pond of lagoon digester after a month of treatment to measure chemical oxygen demand (COD), biological oxygen demand (BOD), total suspended solids (TSS) and pH. The biogas production was estimated and measured using the vortex flow meter, while a portable biogas analyzer was used to measure the biogas quality. The COD concentration of the wastewater before use of the digester was 35,000 mg/L which was above the standard of Ministry of Environment, Cambodia (<70 mg/L of COD for a public water discharging) which was reduced to 12,000 mg/L, or 65%, after treatment. It was estimated that the biogas yield from the lagoon digester was, on average, 2,296.9 Nm3/day. While the H2S concentration was over 5,000 ppm (above the permittable standard < 200 ppm) and the CH4 content was 52%. In conclusion, this factory can lower the COD concentration of mango wastewater after discharging from the lagoon digester and further benefit from using biogas instead of LPG gas for cooking; by using the lagoon digester, the factory may be able to reduce greenhouse gas emissions by 1,5415.6 tCO2eq/year.
