Biological sulphate reduction with primary sewage sludge in an upflow anaerobic sludge bed (UASB) reactor – Part 2: Modification of simple wet chemistry analytical procedures to achieve COD and S mass balances Biological sulphate reduction with primary sewage sludge in an upflow anaerobic sludge bed (UASB) reactor – Part 2: Modification of simple wet chemistry analytical procedures to achieve COD and S mass balances Posted in .