Sustainable WSP design
The Problem
Waste stabilization ponds (WSP) are a cost-effective way for treating human wastes in developing countries; however, they lead to eutrophication of receiving waters if not properly maintained, which is often the case when tax revenues are inadequate to support O&M costs (like in developing countries). Moreover, sustainably sourced fishmeal and fish oil are needed for aquaculture as are methods to mitigate short-term greenhouse gases such as methane.
Our Proposal
WSPs can act as hatcheries for native detritivores. WSP operators or third party entrepreneurs who lease space and access to WSP effluent may be the owner-operator of a hatchery system. Adult fish, native to the location of the WSP, are i) broodstock for the hatchery rather than sold for consumption and ii) are reared on microbial biomass that accumulates in the secondary and tertiary ponds which reduces WSP dredging frequency. Plankton recovered from ponds is food for fingerling fish in the hatchery, and revenue from fingerling sales supports proper WSP operation which eliminates nutrient breakthrough into receiving waters. Farmers, aquaculture operators, and aquaponics operators are potential purchasers of fingerlings. For instance, fingerling fish transition to feeding on detritus as they grow, and rice farmers may rear fish in inundated rice fields. Once harvested, they can provide revenue to farmers either as fish for human consumption since they are grown outside of the WSP environment or as a sustainable source of fishmeal/fish oil for aquaculture operations. Additionally, detritivorous fish remove excess carbon from inundated fields as they grow, which reduces rice field methane (a potent greenhouse gas) production. Moreover, integrated multi-trophic aquaculture operators can use detritivorous fish as a means to reduce feed and feces waste from carnivorous fish growth pens, and aquaponics operators can use the fish to reduce the need for exogenous fish food.
We Assume that...
Economic viability can be achieved while realizing environmental success
Phytoplankton and zooplankton biomass from WSP nutrient loads can support fingerling development
Effluent is sufficiently decontaminated for successful fish growth
Novel aeration strategies are sufficient for rearing fish while being economically and energetically viable
Constraints to Overcome
The project will focus on a prototype demonstration. Key metrics for the demonstration project include technical operational parameters such as dissolved oxygen, nutrient excretion, growth rate, reproductive success, and larva-to-fingerling survival rate. Furthermore, process energy demand will be monitored as will microbial bioburden and stocking density of fingerlings.
Current Work
Demonstrate a process that makes WSPs economically viable and environmentally sustainable regardless of where they are located.
Current Needs
Funding is needed. We have a model system in place but need the fish to conduct the demonstration project. Native fish are a must for this project. The recent drought in California has decimated all know commercial stocks of the native fish needed for the demonstration project. Stocking the prototype system with wild fish is possible, however the regulatory requirements are steep and costly to use wild fish.