Evaluation of DNA extraction methods for freshwater eukaryotic microalgae

The use of molecular methods to investigate microalgal communities of natural and engineered freshwater resources is in its infancy, with the majority of previous studies carried out by microscopy. Inefficient or differential DNA extraction of microalgal community members can lead to bias in downstream community analysis. Three commercially available DNA extraction kits have been tested on a range of pure culture freshwater algal species with diverse cell walls and mixed algal cultures taken from eutrophic waste stabilization ponds (WSP). DNA yield and quality were evaluated, along with DNA suitability for amplification of 18S rRNA gene fragments by polymerase chain reaction (PCR). QiagenDNeasy^® Blood and Tissue kit (QBT), was found to give the highest DNA yields and quality. Denaturant Gradient Gel Electrophoresis (DGGE) was used to assess the diversity of communities from which DNA was extracted. No significant differences were found among kits when assessing diversity. QBT is recommended for use with WSP samples, a conclusion confirmed by further testing on communities from two tropical WSP systems. The fixation of microalgal samples with ethanol prior to DNA extraction was found to reduce yields as well as diversity and is not recommended.     

Environmental factors and management practices controlling oxygen dynamics in agricultural irrigation ponds in a semiarid Mediterranean region: implications for pond agricultural functions

A water quality study was carried out on 40 irrigation ponds located within the main greenhouse areas on the Almería coast, placing special emphasis on the factors controlling the oxygen dynamics, a relevant aspect with agricultural and environmental implications. Considering chemical, physical and biological water characteristics, agricultural irrigation ponds were satisfactorily classified by cluster analysis in four groups. These were congruently arranged by principal components analysis along four main environmental gradients: trophic status, photosynthetic activity, water mineralisation and presence of submerged aquatic vegetation (SAV). Dissolved oxygen (DO) values differed highly among and within each of the four pond groups. DO dynamics was mainly depended on photosynthetic activity, and the environmental factors and management practices controlling it: seasonal and daily climatic changes, pond management (open vs. covered ponds and presence/absence of aquatic vegetation) and trophic status. Overall, different diurnal DO patterns were found between open and covered ponds. The former usually presented DO values above saturation and increasingly higher from early morning to mid-afternoon due to the photosynthetic activity of algae and macrophytic vegetation. In contrast, covered ponds showed relatively stable DO values during the diurnal period regardless of climatic conditions, with absolute values around or below saturation level. Globally, our results suggest that open ponds, with macrophytes concentrated in the deeper layer, can be an effective and sustainable management method of water oxygen enrichment.     

Aerated Rock Filters for Enhanced Ammonia and Fecal Coliform Removal from Facultative Pond Effluents

Rock filters used to treat effluents from waste stabilization ponds do not remove ammonia as they are anoxic. A pilot-scale aerated rock filter was investigated, in parallel with an unaerated control, over an 18-month period to determine whether aeration provided conditions within the rock filter for nitrification to occur. Facultative pond effluent containing ～ 10?mg NH4–N/L was applied to the filters at a hydraulic loading rate of 0.15?m3/m3?day during the first 8?months and at 0.3?m3/m3?day thereafter. The results show that the ammonia and nitrate concentrations in the effluent from the aerated filter were <3 and ～ 5?mg?N/L, respectively, whereas the ammonia concentration in the effluent from the control filter was ～ 7?mg?N/L. Fecal coliforms were reduced in the aerated filter to a geometric mean count of 65?per?100?mL; in contrast the effluent from the control filter contained 103–104 fecal coliforms per 100?mL. Aerated rock filters are thus a useful land-saving alternative to aerobic maturation ponds.     

A contour plot technique for depicting wastewater lagoon parameters and analysing their interrelatedness

Most wastewater treatment plants regularly monitor plant performance. Analysis of the resulting data can provide valuable insights into plant behaviour. A useful first step in the systematic analysis of such data is to depict them graphically. The resulting plots help identify the more obvious relationships between measured wastewater characteristics. They also help in locating anomalous data points. In the case of multi-pond wastewater treatment lagoons, finding an informative way of depicting the monitoring data is difficult. This is because the required data plots need to show not only how measured characteristics vary with time but also how they vary along the pond chain. Conventional 2-D “time-series” plots are inadequate for this task if the lagoon comprises more than a few ponds, or if the amount of accumulated data is large. An alternative, contour plot based approach was developed that overcomes the problems with conventional 2-D plots. The procedure for producing such plots is described and factors affecting their accuracy discussed. A major advantage of the contour plot approach is that contour plots for different parameters can be superimposed. By examining these superimposed plots, one can learn much about the way different parameters are related. A procedure is described that enables the interrelatedness of any given pair of parameters to be systematically characterised. The effectiveness of the contour plot approach is illustrated using data obtained over a 9-year period for an 11 (later 10) pond lagoon at the Western Treatment Plant in Melbourne, Australia.     

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. In this work, luxury uptake was investigated by chemical extraction of the acid-soluble and acid-insoluble fractions of polyphosphate in the microalgae. The results showed that the initial accumulation and subsequent utilization of both acid-soluble polyphosphate (ASP) and acid-insoluble polyphosphate (AISP) is a function of the wastewater phosphate concentration. It was found that light intensity influenced both the accumulation and utilization of ASP. The temperature influenced the accumulation of AISP. AISP is believed to be a form of phosphorus storage and ASP is involved in metabolism however, the results of this work show that ASP can also act as a short term form of phosphorus storage. To optimize luxury uptake by microalgae a ‘luxury uptake pond’ is proposed where the conditions the microalgae are exposed to can be manipulated. This ‘luxury uptake pond’ would be designed to expose the microalgae to a high phosphate concentration and high light intensity for a short period of time in order to achieve optimal polyphosphate accumulation. Subsequent harvesting would then remove the phosphorus rich microalgae from the system.     

Azolla as a source of biomass: a comparison with water hyacinth

Aquatic weeds are known for their high growth potential. In this paper Azolla‐an aquatic free floating fern‐has been considered as a source of biomass. The five aspects, viz., habitat and distribution, habit and morphology, major chemical components, control measures and environmental influences, and utilization aspects have been focused and compared with those of the water hyacinth. The many advantages offered by Azolla over water hyacinth have been demonstrated. The possibility of using Azolla for biogas generation has also been emphasized.     

Use of clays as liners in solar ponds

An alternative to synthetic materials for use in solar pond liners is to select clayey soils as hydraulic barriers. This option reduces the cost of construction and the risk of contamination of subsoil and groundwater by hot brines. This paper deals with the physical, chemical and hydraulic properties of different soils tested mainly as compacted clay liners. The underdeveloped nations have the option to use this type of liner, but before doing so several tests are recommended, including those for soil and water composition, permeability, plasticity and X-ray diffraction analysis. In this investigation the following samples are analyzed: native clayey soils with illite, montmorillonite and halloysite, treated and non-treated bentonites in powder and granulated form, a mixture of zeolite and sodium bentonite, and industrial minerals composed largely of halloysite, kaolinite and attapulgite selected clays. Neutral salt aqueous solutions (NaCl and KCl) at different concentrations and under temperature gradients were used for compatibility testing conducted on these specimens. Experiment setup and particular testing procedures are also discussed.     

Productivity and biochemical composition of Phaeodactylum tricornutum (Bacillariophyceae) cultures grown outdoors in tubular photobioreactors and open ponds

In this study we compared the biomass productivity and the chemical composition of the diatom Phaeodactylum tricornutum grown outdoors at different biomass concentrations, in open ponds and photobioreactors (PBRs). Optimal biomass concentration of 0.6 g L⁻¹ and 1.0 g L⁻¹ was found in open ponds and in PBRs, respectively. During summer the mean net areal biomass yield was 11.7 g m⁻² day⁻¹ and 13.1 g m⁻² day⁻¹ in open ponds and in PBRs, respectively. Night biomass loss was comparable (17.4% and 21.4% of the daylight productivity, in open ponds, and PBRs, respectively). Lipid content ranged between 25% and 27.5% of dry weight, and increased up to 34.7% of biomass grown in dense cultures (>0.6 g L⁻¹ in ponds; >1.0 g L⁻¹ in PBRs). In the evening they ranged between 21% and 31%, while a reduced amount was found in the morning – between 14.5% and 24%. An induction of the diadino–diatoxanthin cycle was observed in the cultures when they were grown at lower biomass concentrations, particularly in cultures grown in photobioreactors, indicating down-regulation of the photosynthetic apparatus due to high irradiance, which was confirmed by a sizeable reduction in the F_v/F_m ratio in the middle of day. It was found that the productivity of cultures was higher in photobioreactors compared to that in open ponds most likely as a result of a better light–dark regime experienced by the cells in short light-path tubular PBRs, which may have allowed a more efficient use of light.     

Biological treatment of chemical industry effluents by stabilization ponds

The aim of the work has been to develop a biological treatment for chemical industry effluents.

A multistage photosynthetic chemostat, fed by chemical industry effluents, was operated continuously as a bench scale experiment aimed at testing the possibility of treating these effluents by means of stabilization ponds. 70–80% of COD and 80–85% of BOD could be removed together with the pesticidal activity present in the raw wastewater. Optimal number of reactors was found to be 6.

Most of the COD and BOD elimination took place during a 30 day detention time. The effluents cannot be considered suitable for free discharge, but can be disposed of by irrigating carefully a halotolerant vegetation.     

Ozone treatment ameliorates oil sands process water toxicity to the mammalian immune system

We evaluated whether ozonation ameliorated the effects of the organic fraction of oil sands process water (OSPW) on immune functions of mice. Ozonation of OSPW eliminated the capacity of its organic fraction to affect various mouse bone marrow-derived macrophage (BMDM) functions in vitro. These included the production of nitric oxide and the expression of inducible nitric oxide synthase, the production of reactive oxygen intermediates and the expression of NADPH oxidase subunits, phagocytosis, and the expression of pro-inflammatory cytokine genes. Ozone treatment also eliminated the ability of OSPW organic fraction to down-regulate the expression of various pro-inflammatory cytokine and chemokine genes in the liver of mice, one week after oral exposure. We conclude that ozone treatment may be a valuable process for the remediation of large volumes of OSPW.