Studies on in-situ measurement and on-line assesment of microbial biomass for predicting the treatment efficiency in a municipal sewage plant

Abstract

The importance of instrumentation, control and automation at municipal sewage plants has increased as a result of stringent treatment requirements and complexity of the process involved. Sustained efforts have been made in the recent years on the reliability and accuracy of online assessment methods for predicting the process performance and treatment efficiency in municipal sewage plants. Development of feasible soft sensors for different purposes in sewage treatment plants has, as well made operation of the plants more advanced. However, critical review of literature has revealed that the on-line biomass measurement is very scarcely adopted and used for the full-scale municipal sewage treatment plants, inspite of the risk due to shock loads and operational failures leading to irreversible operational and economic loss. Hence, in this study a design and application of microbial sensor was considered for maintaining consistent treatment efficiency in municipal sewage plants. Extensive laboratory investigations were carried out to design a conductometric enzyme biosensors for measuring microbial biomass in a municipal sewage plant. The conductometric transducer was designed as thin film electrode using platinum (Pt) and glass materials with enzyme immobilization using proteinase K enzyme for measurement biomass. It was inferred from the present study that at steady state, a balance was established and 10-14 min were required to reach steady state corresponding to 6 measurements per hour. The steady state response (µS) signify a major setback on time of immobilization. It was observed from the study that the effect of phenol is seen to affect the sensor response either in the absence or at low concentrations of chloride and sulphates in the municipal wastewater. Based on the overall observations of microbial biomass assessment on synthetic municipal wastewater without and with inhibition it was realized that the resultswould further deepen the insight on field level understanding and interpretations of biomass.