Fecal Coliform Level Determination in Surface Water Used for Irrigation in New Jersey

A water quality assessment is necessary when fruit or vegetable operations are evaluated for possible sources of microbial contamination.  Surface water irrigation has become more of a concern as reported food borne illnesses have increased.  Irrigation water in New Jersey was analyzed for fecal coliform to determine if another water source should be selected or a treatment system installed. 

A two-year study was carried out to determine fecal coliform levels in surface water used for irrigation.  Five locations were sampled on a weekly using standard procedures recommended by the commercial laboratory analyzing the samples.  Sampling locations consisted of (1) a river with suburban and industrial areas up stream, (2) a spring-fed pond with some runoff from surrounding fields, (3) a dam on a stream with agricultural areas up stream, (4) a spring-fed pond with no runoff entering and (5) a pond located in an agricultural area with runoff from surrounding fields and wildlife activity. 

In 2008, fecal coliform mean levels (colony forming units/100 ml of water) for four sampling dates were lowest at locations 2 and 4 (33 and 61 cfu/100 ml) and highest at location 5 (1339 cfu/100 ml).  The river site (location 1) averaged 283 cfu/100 ml while the dam (location 3) had 174 cfu/100 ml. 

In 2009, ten dates were sampled to better monitor the whole production season.  The results were similar to 2008 where locations 2 and 4 had the lowest levels of fecal coliform (176 and 49 cfu/100 ml) and the highest at location 5 (289 cfu/100 ml).  Location 1 (river site) averaged 293 cfu/100 ml and the dam location (3) averaged 138 cfu/100 ml.  The river (location 1) and runoff pond site (location 5) had levels above what would be considered acceptable in New Jersey for irrigation water (200 cfu/100 ml).  Mean high colony counts for fecal coliform were the result of runoff during rain events and wildlife pressure.  In these locations, growers should irrigate from a ground water source or use a pond where there is little chance of runoff or wildlife activity.