Probiotic effects of anaerobic co-digestion substrates.

Manure is often added to stabilise anaerobic digesters especially when co-digesting high-energy substrates such as whey. While different researchers have attributed its beneficial effect to various components including alkalinity, nutrients or trace elements this research instead aimed to determine whether microorganisms, such as lactic acid bacteria which are naturally present in the feedstocks, were having a notable beneficial effect on biogas production. Casein whey and cow manure were co-digested with primary sludge and produced 151.

The biosynthesis of nitrous oxide in the green alga Chlamydomonas reinhardtii.

Over the last decades, several studies have reported emissions of nitrous oxide (N O) from microalgal cultures and aquatic ecosystems characterized by a high level of algal activity (e.g. eutrophic lakes).

Photodegradation and sorption govern tetracycline removal during wastewater treatment in algal ponds.

The degradation of the antibiotic tetracycline, supplied at 100µgL in domestic wastewater, was studied in an outdoor, pilot scale, high rate algal pond (HRAP). Effective operation was demonstrated with the biomass concentration and the chemical oxygen demand removal efficiency averaging 1.2±0.

Emerging contaminant degradation and removal in algal wastewater treatment ponds: Identifying the research gaps.

Whereas the fate of emerging contaminants (ECs) during 'conventional' and 'advanced' wastewater treatment (WWT) has been intensively studied, little research has been conducted on the algal WWT ponds commonly used in provincial areas. The long retention times and large surface areas exposed to light potentially allow more opportunities for EC removal to occur, but experimental evidence is lacking to enable definite predictions about EC fate across different algal WWT systems. This study reviews the mechanisms of EC hydrolysis, sorption, biodegradation, and photodegradation, applying available knowledge to the case of algal WWT.

Maximizing Productivity and Reducing Environmental Impacts of Full-Scale Algal Production through Optimization of Open Pond Depth and Hydraulic Retention Time.

The ability to dynamically control algal raceway ponds to maximize biomass productivity and reduce environmental impacts (e.g., land and water use) with consideration of local constraints (e.

Algal recycling enhances algal productivity and settleability in Pediastrum boryanum pure cultures.

Recycling a portion of gravity harvested algae (i.e. algae and associated bacteria biomass) has been shown to improve both algal biomass productivity and harvest efficiency by maintaining the dominance of a rapidly-settleable colonial alga, Pediastrum boryanum in both pilot-scale wastewater treatment High Rate Algal Ponds (HRAP) and outdoor mesocosms.

Algal productivity modeling: a step toward accurate assessments of full-scale algal cultivation.

A new biomass productivity model was parameterized for Chlorella vulgaris using short-term (<30 min) oxygen productivities from algal microcosms exposed to 6 light intensities (20-420 W/m(2)) and 6 temperatures (5-42 °C). The model was then validated against experimental biomass productivities recorded in bench-scale photobioreactors operated under 4 light intensities (30.6-74.

Full-scale validation of a model of algal productivity.

While modeling algal productivity outdoors is crucial to assess the economic and environmental performance of full-scale cultivation, most of the models hitherto developed for this purpose have not been validated under fully relevant conditions, especially with regard to temperature variations. The objective of this study was to independently validate a model of algal biomass productivity accounting for both light and temperature and constructed using parameters experimentally derived using short-term indoor experiments. To do this, the accuracy of a model developed for Chlorella vulgaris was assessed against data collected from photobioreactors operated outdoor (New Zealand) over different seasons, years, and operating conditions (temperature-control/no temperature-control, batch, and fed-batch regimes).

Investigating the life-cycle and growth rate of Pediastrum boryanum and the implications for wastewater treatment high rate algal ponds.

The colonial alga Pediastrum boryanum has beneficial characteristics for wastewater treatment High Rate Algal Ponds (HRAP) including high biomass productivity and settleability. Our previous work has shown that these characteristics are enhanced when a portion of gravity harvested algae is recycled back to the pond. To help understand the mechanisms behind the improved performance of P.

Modeling the effects of light and temperature on algae growth: state of the art and critical assessment for productivity prediction during outdoor cultivation.

The ability to model algal productivity under transient conditions of light intensity and temperature is critical for assessing the profitability and sustainability of full-scale algae cultivation outdoors. However, a review of over 40 modeling approaches reveals that most of the models hitherto described in the literature have not been validated under conditions relevant to outdoor cultivation. With respect to light intensity, we therefore categorized and assessed these models based on their theoretical ability to account for the light gradients and short light cycles experienced in well-mixed dense outdoor cultures.

Active slag filters: rapid assessment of phosphorus removal efficiency from effluent as a function of retention time.

There is increasing pressure to upgrade effluent ponds for phosphorus removal. Active slag filters offer a solution, but design information is limited. Hydraulic retention time (HRT) is a key factor in filter design because it controls filter treatment efficiency as well the filter substrate lifespan.

Variability and uncertainty in water demand and water footprint assessments of fresh algae cultivation based on case studies from five climatic regions.

Using case studies from five typical climatic locations, this study revealed that current quantification of water demand (WD) and water footprint (WF) of freshwater algae cultivation in raceway ponds suffer from uncertainty and variability in the methodologies and assumptions used. Of particular concern, the WF metric had an intrinsically poor geographical resolution and could be biased towards high-productivity arid locations because local levels of water stress are not accounted for. Applying current methodologies could therefore cause the selection of locations that are neither economically viable nor environmentally sustainable.

Outdoor cultivation of temperature-tolerant Chlorella sorokiniana in a column photobioreactor under low power-input.

Temperature-tolerant Chlorella sorokiniana was cultivated in a 51-L column photobioreactor with a 1.1 m(2) illuminated area. The reactor was operated outdoors under tropical meteorological conditions (Singapore) without controlling temperature and the culture was mixed at a power input of 7.

Tracer studies on an aerated lagoon.

The city of Palmerston North, New Zealand, has two aerated lagoons as its secondary treatment facility. Interest about treatment efficiency led to an investigation into the hydraulics in the second lagoon to determine if further optimisation was viable. A tracer study using rhodamine WT was undertaken to ascertain the stimulus response output.

Universal temperature model for shallow algal ponds provides improved accuracy.

While temperature is fundamental to the design and optimal operation of shallow algal ponds, there is currently no temperature model universally applicable to these systems. This paper presents a model valid for any opaque water body of uniform temperature profile. This new universal model was tested against 1 year of experimental data collected from a wastewater treatment high rate algal pond.

Sustainable sunlight to biogas is via marginal organics.

Although biogas production from algae offers higher sunlight to biomass energy conversion efficiencies its production costs simply cannot compete with terrestrial plants. Unfortunately terrestrial plant cropping for biogas production is, in its own right, neither particularly sustainable nor profitable and its ongoing application is only driven by energy security concerns resulting in taxpayer subsidies. By comparison, scavenging the organic energy residual/wastes from food production offers a far more profitable and sustainable proposition and has an energy potential that dwarfs anything biogas production from dedicated energy crops can realistically offer.

Mechanistic modeling of broth temperature in outdoor photobioreactors.

This study presents the first mechanistic model describing broth temperature in column photobioreactors as a function of static (location, reactor geometry) and dynamic (light irradiance, air temperature, wind velocity) parameters. Based on a heat balance on the liquid phase the model predicted temperature in a pneumatically agitated column photobioreactor (1 m(2) illuminated area, 0.19 m internal diameter, 50 L gas-free cultivation broth) operated outdoor in Singapore to an accuracy of 2.

Towards a luxury uptake process via microalgae--defining the polyphosphate dynamics.

Microalgae in waste stabilization ponds (WSP) have been shown to accumulate polyphosphate. This luxury uptake of phosphorus is influenced by the wastewater phosphate concentration, light intensity and temperature, but the dynamics of how these factors affect luxury uptake with respect to time are not understood. With improved understanding of the dynamics of this mechanism and how it could be manipulated, a phosphorus removal process utilizing luxury uptake by microalgae might be developed.

Phosphorus removal mechanisms in active slag filters treating waste stabilization pond effluent.

Phosphorus (P) removal mechanisms from waste stabilization pond effluent by a melter slag filter were investigated. The studied filter had treated pond effluent for a decade, but lost its P removal efficiency after 5 years. The P distribution in the slag was examined by scanning electron microscopy (SEM), electron dispersive spectrometry (EDS), X-ray fluorescence (XRF), X-ray diffraction (XRD), and chemical fractionation.

Enhanced biological phosphorus removal for high-strength wastewater with a low rbCOD:P ratio.

In order to assess the feasibility of enhanced biological phosphorus removal (EBPR) for dairy processing wastewater, which in New Zealand have rbCOD:P ratios that can be as low as 13:1, a sequencing batch reactor treating a synthetic wastewater with a COD(VFA) of 800 mg/l (representing a dissolved air flotation (DAF) treated, pre-fermented dairy wastewater with a raw COD of 3000 mg/l) was operated at COD:P ratios of 25:1, 15:1 and 10:1. Full (>99%) phosphate removal was achieved for COD:P loadings of 25:1 and 15:1. The trial using 10:1 COD:P loading showed less consistency but still achieved 82% phosphate removal.

Phosphorus removal by an 'active' slag filter-a decade of full scale experience.

Active filters, which facilitate phosphorus (P) removal via precipitation and/or adsorption, offer a promising 'appropriate technology' for upgrading small wastewater treatment systems. Research on active filters for P removal using steel slag material has been conducted in laboratories across the world, however, field experiments have been limited and long-term data is practically non-existent. This paper presents a decade of experience on P removal by active slag filters at a full-scale treatment plant.