Comparative study of wastewater lagoon with and without water hyacinth [Eichhornia crassipes, biological filters]

A 3-year study was conducted on an existing, one-cell, facultative sewage lagoon having a total surface area of 3.6 ha and receiving a$BOD_{5}$loading rate of 44 kg/ha/d (40 lb/a/d). The comparative experimental periods ran from July through November for 3 consecutive years. During the first period, water hyacinths completely covered the lagoon. The water hyacinth coverage was reduced to 33% of the total surface area the second year. The lagoon, free of all vascular aquatic plants the third year, was monitored for comparative purposes. The most significant improvement overall in the effluent quality occurred when water hyacinths covered the entire lagoon. During this period the effluent$BOD_{5}$and TSS were 23 and 6 mg/l, respectively. Without water hyacinths, the effluent$BOD_{5}$and TSS were 52 and 77 mg/l, respectively. The effluent total organic carbon concentration with water hyacinths averaged 40 mg/l, and without water hyacinths, 72 mg/l. A discussion of the results from this 3-year study is presented in this paper along with associated problems that were observed when water hyacinths were introduced into the lagoon and altered its behavior from that of a normal facultative lagoon.