Amongst the technologies available, the up flow anaerobic sludge blanket (UASB) process has been one of the most widely applied methods for municipal waste water treatment especially in countries of warm climatic conditions like India.  However, past about one decade has witnessed rapid decline in the UASB popularity and its implementation. There has been criticism from various sections on the performance of UASB reactors for not complying with the prescribed discharge standards. It is a general hypothesis that the UASB reactors are not meant for diluted waste water like municipal sewage when typically the BOD is less than 150 mg/l, COD 250 mg/l and sulphates are more than 150mg/l. An attempt has been made through this study to investigate the reasons on the basis of quality assessment and field observations on UASB reactors and it’s post-treatment of a newly commissioned (start-up) municipal (sewage) wastewater treatment plant commonly called ‘STP’ having capacity of 14 million litres per day (MLD). Study was aimed to know the gaps during the commissioning stage which could be related to poor removal efficiencies. This paper briefly discusses some issues related to operation and maintenance of the UASB plants with purpose for improvements.