Concentration, Temperature and Storage duration Influence Chemical Stability of Compost Tea

Chemical stability is one of the key quality control criterion for complex degradable materials with an active microbial community like compost tea, but largely understudied. A laboratory study was performed to assess the chemical stability of varying concentrations (0, 2.5, 5, 10, 15, 20, 30, 50 and 100%) of municipal solid waste (MSW) compost tea stored at different temperatures (4°, 10°, 22° and 35°C) and storage time (0, 13, 26 39 and 52 days). A 2-dimension principal component biplot confirmed close relationship amongst total dissolved solids (TDS), electric conductivity (EC) and salinity while pH was less related and turbidity was isolated. TDS in the MSW compost tea did not change at a storage temperature of 4oC or 10oC but was significantly (P<0.05) increased by 4.3% when the storage temperature was raised to 35oC. Also, TDS increased sharply from 93.25 mg/L on day 1 to 111.31 mg/L on day 26 after which it remained unchanged. EC increased by approximately 8% only when the MSW compost tea was stored at 35oC. The EC on the other hand increased by 19.4% from 131.28 µS/cm on day 1 when it peaked on day 26 and plateaued off to day 52. The change in pH was small and ranged from 7.44 to 7.67. Concentration had the strongest association with TDS, EC, salinity and turbidity and did not vary with storage time nor temperature. A multilinear regression (Y = αD + βC + γT + k) showed significant (P<0.05) coefficients for all the independent variables except the coefficients for temperature in the turbidity, salinity and pH regression models. In conclusion, the chemical stability of the MSW compost tea was dependent on the storage temperature and storage duration. Chemical stability was reached after 26 days of storage while cold storage at 4oC or 10oC reduced chemical alteration.