The main resource recovery scheme which is of general interest everywhere, but of specific interest in Penang, is energy gain through anaerobic digestion in biogas production. Recovery of nutrients can be accomplished either by husbanding micro-organism or macro-organisms, such as fish. Besides economics, a major constraint will be land resources, particularly if wastewater processing is done through macro-organisms (Taiganides, 1979).
Taiganides, in his report, has made some tentative, preliminary calculations on the land area requirements for a pig population of 11 000 pigs of 55 kg average weight (from piglets to boars), and the results are given in Tables 10.2 and 10.3 (11 000 is the pig population size at Batu Maung (see also Item 2.2.1). Estimated quantities and characteristics for the Batu Maung pig area are given in Table 10.3.
Table 10.3 also shows some general constraints to general alternatives. The main constraints of course are land and energy. The alternatives which do not require energy inputs, but do recycle the wastes, have high land requirements. On the basis of land requirements alone, fishponds and shrimp ponds for the entire flow become prohibitive. However, this does not mean that fish or shrimp ponds could not be part of an overall integrated system. For example, a good integrated system could be anaerobic digestion of solids, aeration or high rate algae ponds for liquids, followed by fish or shrimp ponds for tertiary treatment/reuse. Such a system would reduce considerably the land requirements and bring them within the approximately 10 hectares of reclaimed land which the State Government would allocate to the Project.
If only one simple treatment, rather than an integrated treatment system were to be constructed, then the first choices, according to the “Index Rank” of Table 10.3, are Anaerobic Digestion, High Rate Algae Ponds, and Aerated Lagoons. Second choices would be Anaerobic Lagoon, and Oxidation Ditch. Oxidation Ponds, Fish and Shrimp Ponds would have too high land requirements. On the basis of cost alone, i.e. initial investment for land, construction and equipment, anaerobic lagoon would be cheaper than all the other methods by a factor of 2 to 6. However, the effluent would not be of acceptable quality. Of course, land costs would influence the cost significantly. If land is gratis, then the ranking could change and oxidation ponds could become more feasible.
The State of Penang is very much interested in the utilization of the pig wastes for resources recovery and for the fertilization of fish production ponds.
