3 Table 2 shows typical influent, primary effluent and duckweed system effluent data for the Mirzapur experimental wastewater treatment plant. S. and elsewhere have produced better than secondary effluent quality for flows ranging from a few hundred cubic meters per day to over 30,000 m 3 /day. 4 Even higher flow rates are being designed for large cities with hundreds of thousands of inhabitants. S. Environmental Protection Agency and other similar regulatory agencies in various countries. 3 The wastewater effluent from the Kumudini Hospital complex (Mirzapur), with BOD of 120 mg/I, is not typical of most developing country wastewater streams which are commonly more polluted.

Photosynthetic activity ceases, temperature gradients are exaggerated, mixing slows, and the zone becomes increasingly anoxic. Compost and manures, as well as commercial fertilizers, are acceptable inputs to carp polyculture. The correct type and quantity of fertilizer to apply depends on pond chemistry as well as on fish density, and these requirements vary seasonally and with locality. Managing pond fertility consists of estimating how much a given amount of fertilizer will contribute to overall biochemical oxygen demand (BOD) in addition to the BOD contribution of fish and feed wastes.

Both are intensive processes that need a steady flow of investment. Credit for these linked processes is characterized by two features: (1) it is appropriately disbursed continuously in small, productivity-based increments, and (2) it is considerably greater than the credit required for comparable conventional farming processes. Where wastewater is the source of water and growth nutrients for duckweed production, lower recurrent costs mean that credit requirements will be about half those for hydroponic culture of duckweed.