High rate algal ponds (HRAPs) are shallow, paddlewheel-mixed open raceway ponds that are an efficient and cost-effective upgrade for the conventional wastewater treatment ponds used by communities and farms the world over. HRAPs provide improved natural disinfection and nutrient removal and can be further enhanced by carbon dioxide (CO 2 ) addition to promote algal growth which is often carbon limited. This paper discusses the construction and operation of a 5-ha demonstration HRAP system treating primary settled wastewater at the Christchurch wastewater treatment plant, New Zealand. The system consisted of four 1.25-ha HRAPs that were constructed from an existing conventional pond. Algae were harvested from the HRAP effluent in specially designed settlers, which concentrated the algal/bacterial biomass to 1-2% organic solids for conversion to bio-crude oil following dewatering. Performance data from the first 15 months of HRAP operation (without CO 2 addition) are presented. The four demonstration HRAPs had reasonable replication of both treatment performance and algal/bacterial productivity with similar annual average wastewater treatment efficiency (~50% removal of BOD 5 ,~87% removal of fBOD 5 ,~65% removal of ammoniacal-N,~19% removal of dissolved reactive phosphorus and~2 log removal of Escherichia coli), algal species composition and algal/bacterial biomass production (~8 g m −2 day −1 volatile suspended solids). These results were in good agreement with the results for pilot-scale HRAP without CO 2 addition in New Zealand. This study provides further indication of the potential for energy efficient and effective wastewater treatment using HRAP, while biofuel conversion of the harvested algal bacterial biomass could provide a valuable niche distributed energy source for local communities.

Mankind has recognized the value of land plants as renewable sources of food, medicine, and materials for millennia. Throughout human history, agricultural methods were continuously modified and improved to meet the changing needs of civilization. Today, our rapidly growing population requires further innovation to address the practical limitations and serious environmental concerns associated with current industrial and agricultural practices. Microalgae are a diverse group of unicellular photosynthetic organisms that are emerging as next-generation resources with the potential to address urgent industrial and agricultural demands. The extensive biological diversity of algae can be leveraged to produce a wealth of valuable bioproducts, either naturally or via genetic manipulation. Microalgae additionally possess a set of intrinsic advantages, such as low production costs, no requirement for arable land, and the capacity to grow rapidly in both large-scale outdoor systems and scalable, fully contained photobioreactors. Here, we review technical advancements, novel fields of application, and products in the field of algal biotechnology to illustrate how algae could present high-tech, low-cost, and environmentally friendly solutions to many current and future needs of our society. We discuss how emerging technologies such as synthetic biology, highthroughput phenomics, and the application of internet of things (IoT) automation to algal manufacturing technology can advance the understanding of algal biology and, ultimately, drive the establishment of an algal-based bioeconomy.

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High rate algal pond (HRAP) systems provide opportunities for low-energy wastewater treatment and energy recovery from wastewater solids, as well as biofuel production from the harvested algal biomass. The wastewater is pretreated using covered anaerobic ponds or gravity settlers and covered digester ponds which remove and digest the wastewater solids. The effluent is then treated in shallow gently mixed HRAP which efficiently breakdown the dissolved organic matter. The algae assimilate wastewater nutrients to provide both secondary and partial tertiary-level treatment. HRAP also provide more efficient natural disinfection. HRAP performance can be further enhanced by bubbling CO 2 into the pond during the day to promote algal growth when it is often carbon-limited. This paper discusses the design and operation and performance of HRAP systems and their application for economical, low-energy upgrade of conventional wastewater treatment ponds combined with energy recovery and biofuel production.