Feasibility of Novel Quadric (Egg-Shaped) Sludge Digesters within Wastewater Treatment Plants Hydraulic Infrastructure across the Caribbean


Wastewater infrastructure across the Caribbean has been actively advancing due to the need to manage water as a resource in a cost-effective manner. Most wastewater treatment facilities across small island developing states (SIDS) stop treatment after the primary stage. Individual Caribbean government’s infrastructural ministries weighs the benefits of various wastewater treatment processes thus making decisions to allow for either disposal of sludge after the primary stage or to provide further treatment. The latter comes at a higher cost, both for initial construction and maintenance. One secondary treatment component that can be beneficial to the Caribbean region is the Quadric-shaped Sludge Digester (QSD). Also commonly known as the egg-shaped sludge digester, it has proven itself to be cost effective during the secondary treatment phase of wastewater sludge. The QSD’s basic form can be described as a revolution of a parabola where the polar regions are either curved or conical. This provides a greater surface area to volume ratio, where the plan area of the sludge reactor is considerably small. Settled sludge can be removed easier thus reducing the power requirements needed when compared to conventional cylindrical tanks. This type of digester (egg-shaped) reduces maintenance costs as a result of the seamless circulation mixing patterns which eliminates girt build-up and the need to halt operations for cleaning and maintenance services. Previous research into the dynamic responses to seismic activity has already been conducted via numerical and scaled earthquake simulation laboratory models. Favourable seismic performance under earthquake simulation table testing has proven the use for these sludge reactors in seismic zones. Construction costs, usually, is the determining factor which dissuades clients from moving forward with the QSD. However, with new advances in materials, construction techniques, structural integrity, the cost and complexity of construction and maintenance can be significantly reduced, thus making it affordable both in terms of economics and construction logistics. This paper outlines ongoing research which illustrates the benefits QSD can be as novel hydraulic infrastructure within existing Caribbean wastewater treatment plants for islands and small economy territories.


Kiran Tota-Maharaj and Navin Ramroop