2.2. Sampling techniques and handling
Samples for chemical analysis were collected using plastic bottles while those for biological analysis were sampled using sterilized plastic bottles. Sampling was done into two phases, the first phase was on August to September 2013 and the second phase was on December 2013 to January 2014. The first phase was in dry season and it was the time before the rice gets matured where the irrigation water demand was low. The second phase was in wet season the time people were planting paddy crops and the water demand at that time was high. The sampling time in both phases was at 9 a.m in the morning and the sampling frequency was twice a week. The sampling techniques and protocol were as per the standards methods for water and wastewater examination (APHA, 1999).
After sampling the samples for Nitrate and Phosphorus were sent to the laboratory and were analyzed within 4 h. Biological samples were prepared in accordance to the standard procedures and incubated for 24 h. Whenever it was not possible to do the analysis immediately, samples for Chemical Oxygen Demand (COD) were acidified using Sulfuric Acid to pH of 2 and stored at 4 °C temperature.