Contribution of effluent from medical institutions to municipal waste water mercury

Twenty-eight hospitals were selected from a total of 113(using standard sampling procedures)that contribute effluent to Gaobeidian sewage treatment plant in Beijing.The density and total amount of mercury(Hg) in the drainage systems of sampled hospitals were analyzed for Hg sources flowing into the Gaobeidian sewage treatment plant.Meanwhile released Hg amount by hospital,bed number and clinic number was analyzed and correlated.The results show high Hg densities in drainage systems from sampled hospitals.An empirical relationship exists between released Hg amount(Y)from hospital,bed number(X₁),and clinic number(X₂):Y=3.11X₁+0.098X₂ +166.94.Total Hg amount released from the hospitals into the Gaobeidian sewage treatment plant area is 99.6g/d,and total Hg amount that enters into the Gaobeidian sewage treatment plant is 828.0g/d.Thus the addition percentage of Hg entering into the sewage treatment plant from hospitals is 12.02%，meaning that the hospitals are not major Hg source of the plant.