Study of the effect of sewage discharge on the microbial quality of the surface sea water from Mount Lavinia to Bambalapitiya

Abstract

Thepresentstudy focused on sewage pollution in the coastal belt from Mount Lavinia to Barnbalapitiya.Sewage pollution was quantified by the membrane fIlter method and the most probable number method for surface sea water samples taken at twelve sampling stations,with two sub samples taken at 100 m and 200 m distance from the shore line. Faecalpollutionwas ubiquitousin the sea water samples studied, and the faecal colifonn counts ranged ft'om 2,725 /100 ml at North of Mount Lavinia Hotel (1\113)to 176,075 1100ml at Wellawatta Canal (W2); faL:cal~treptococcus counts ranged from 26 /100 ml at Bambalapitiya railway Station (B3) to 6.783.83 /100 ml at Wellawatta Canal (\V2); totalcolifonTIcounts ranged from 3,030 /100 ml at BambalapitiyaPolice Station (B2) to 507.558/100 ml at Wellawatta Canal (\"\72).The MPN counts done for the five selected samplingstations revealed that E. coli counts ranged from 2,270 /100 ml at Mount LaviniaHotel (M2) to 259,229 /100 ml at \Vellawatta Canal (W2). Faecalbacterial counts in the surface sea waters along the coast were velYheterogeneous b:omone area to another. Faecal colifonn counts showed a decreasing sequence in the followingorder: W2 (176.075 * 103/100ml) > \~l3 (44.557 * 103/100ml) > D2 (39.025 * 103/100ml) > D1 (38.1 * 103/100ml) > WI (12.57 * 103/100ml) > B1 (11.892 * 103 /100ml) > D3 (9.297 * 103/100ml) :>B3 (7.683 * 103/100ml) > B2 (7.375 * 103/100 ml)> M1 (2.725 * 103/100ml) > 1v12(2.308 * 103/100 ml) > M3 (2.273 * 103/100ml). Faecal streptococcus counts showed a decreasing sequence in the following order: W2 (6,783.83/100 rnI) > D2 (642.75 /100 rnI) > Dl (611.15/100 rnI) > W3 (317.75/100 ml) > D3 (203.085/100 ml) > Bl (116.58/100 ml) > WI (109.5 /100 rnI) > B2 (65.67 /100 ml) ::-..M3 (39.415 il00 ml) > ]\Ill (34.415 /100 ml) > M2 (31.415 /100 rnI) > B3 (26 i100 ml). Total colifonn counts showed the following decreasing sequence: W2 (507.997 >I 02 (51.972 * lOJ/l(~OrnI)> \V3 (51.808 >I< 10'/100 ml) > WI (23.577 >I B1 (18.0 >II D1 (12.31 >I B3 (10.448 >I 1\'13(4.69 >I M1 (4.379>1 Ivf2(3.965 * 103,,100 rot) > B2 (3.03>1 Most probable number of E. coli showed a decreasing sequence as follows: W2 (259.229 * 103/100 rol) > 02 (36.017 * 103/100 ml) > WI (5.713 >I B2 (3.12 >I Wellawatta Canal had a significant sewage polluting effect (FC = 176,075 /100 rnI; FS = 6.783.83 /100 m1; TC = 507,998 /100 rnI) at 95% confidence level. There was no significant difference between 100 m and 200 m distances away from the shore, with respectto sewage pollution at each sampling station.