Nitrogen Loading from Septic Tanks in the Coastal Plains

Abstract

The major non-agricultural source of nitrate in groundwater is septic-soak pit systems and unsewered conditions in the east coastal plains of India. This paper deals with the assessment of nitrogen loading from septic tanks in the Kakinada urban east coastal plains of Andhra Pradesh State, India. The proposed assessment methodology makes use of available databases of population, number of houses, sanitary information, soil types etc., in each village or sub-basins which are generally available in India or elsewhere. Two-dimensional Fuzzy c-Means clustering Technique (2 D FCM) was used to classify nitrogen load over the Kakinada urban coastal plain into low, medium and high zones. Further, these zones were validated with the respective average groundwater quality. The average groundwater nitrate and electrical conductivity values are following the patterns of nitrogen loading zones. Therefore, groundwater nitrate contamination is mainly due to the unsewered conditions and high density of septic systems in the study area. The methodology adopted in the present paper is useful for the assessment of nitrogen load from leaky septic systems in the coastal plains and also for prioritizing the villages or sub-basins for better management of non-agricultural sources of nitrate in coastal plains.