Algal polymorphism in high rate wastewater treatment ponds

In the past as well as today there have been two conflicting opinions as to whether changes in the algal species in water bodies indicate polymorphism or the development of separate species. Similar changes were also found in High Rade Algae Pond (HRAP) used for wastewater treatment, effluent reclamation and protein production. To critically examine both opinions, samples of HRAP effluent were taken and the algal species identified and measured continuously, using conventional methods.Two main algal species were identified. These remained stable during all four monitoring sessions over a three-year period. The external changes observed in the algae were a reflection of controlled periods of organic loading and the conditions under which the pond was operated, such as retention time (a dependant of radiation), ambient temperature, effluent depth and aeration methods.Current address: Institute for Desert Research, Ben-Gurion University of the Negev, Sde-Boker, Israel 84990     

Effect of nutrient loading and retention time on performance of high rate algal ponds

Small pilot ponds in a glasshouse at the Scottish Agricultural College (Auchincruive) were used to investigate the effects of changing C:N:P loading rate and retention time on pond performance as measured by nutrient removal and dry matter biomass. One experiment investigated ponds operated at two C:N:P ratios: low (9:7:1) and high (104:10:1) and two retention times (4 and 7 days θ. Increasing retention time from 4 to 7 days increased the concentration of total (dry matter) and algal (chlorophyll a) biomass and the degree of nitrification. It also increased removal of phosphorus, but had no effect on nitrogen or COD removal. Cyanobacteria predominated in ponds operated at both 4 and 7 days, and the density of cyanobacteria increased with increased retention time. Nitrogen removal was independent of C:N:P ratio; indeed the lower C:N:P ratio favoured increased nitrification. A high C:N:P ratio increased phosphorus and COD removal and increased the concentration of algal biomass (chlorophyll a), but had little effect on total biomass (dry matter). A second experiment varied COD loading rate (600, 350 and 100 kg COD ha-¹ d-¹) while maintaining a constant retention time (either 5 or 7 days θ). Species composition was independent of retention time. The longer retention time increased both total and algal biomass concentration and also percentage of nitrogen removed. Nitrification was independent of retention time. Increasing loading rate increased dry matter production and resulted in a predominance of cyanobacteria over Chlorophyceae. Increased loading rate was related to increase in nitrogen removal, however more complete nitrification occurred at low COD loading rates. Phosphorus removal in the pond with 5-day (θ) remained constant independent of loading rate, but in the pond with 7-day θ phosphorus removal increased with increased COD loading. COD removal was independent of both retention time and loading rate. This revised version was published online in August 2006 with corrections to the Cover Date.     

Hectare-scale demonstration of high rate algal ponds for enhanced wastewater treatment and biofuel production

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 (CO₂) 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 CO₂ 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 BOD₅, ~87% removal of fBOD₅, ~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 CO₂ 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.     

An integrated algal sulphate reducing high rate ponding process for the treatment of acid mine drainage wastewaters

Acid mine drainage pollution may be associated with large water volume flows and exceptionally long periods of time over which the drainage may require treatment. While the use and role of sulphate reducing bacteria has been demonstrated in active treatment systems for acid mine drainage remediation, reactor size requirement and the cost and availability of the carbon and electron donor source are factors which constrain process development. Little attention has focussed on the use of waste stabilisation ponding processes for acid mine drainage treatment. Wastewater ponding is a mature technology for the treatment of large water volumes and its use as a basis for appropriate reactor design for acid mine drainage treatment is described including high rates of sulphate reduction and the precipitation of metal sulphides. Together with the co-disposal of organic wastes, algal biomass is generated as an independent carbon source for SRB production. Treatment of tannery effluent in a custom-designed high rate algal ponding process, and its use as a carbon source in the generation and precipitation of metal sulphides, has been demonstrated through piloting to the implementation of a full-scale process.The treatment of both mine drainage and zinc refinery wastewaters are reported. A complementary role for microalgal production in the generation of alkalinity and bioadsorptive removal of metals has been utilised and an Integrated 'Algal Sulphate Reducing Ponding Process for the Treatment of Acidic and Metal Wastewaters' (ASPAM) has been described.     

High rate algal pond operating strategies for urban wastewater nitrogen removal

Two experimental high rate algal ponds (HRAPs) (1.5m², 570 L per unit), each with a secondaryclarifier for algal biomass separation (0.025 m²,without recirculation), were fed with urban wastewaterfor a one-year period (June 1993 to July 1994). TheHRAPs were installed on the roof of the Department ofHydraulic, Coastal and Environmental Engineering ofthe Technical University of Catalonia, Barcelona,Spain (lat. 41^° 24 42 N; long. 2^° 742 E). Nitrogen removal efficiency and changes intotal nitrogen, total organic nitrogen,NH₄ ⁺-N, and oxidized nitrogen underdifferent hydraulic retention times (HRTs) werecompared. HRAP A was always operated at a higherHRT than HRAP B. Both HRAPs were subjected to thesame environmental conditions of solar radiation, airtemperature and influent water quality. Grab samplesof influent, effluent of the HRAP (mixed liquor) andfinal effluent from the clarifiers were taken once aweek. The annual average nitrogen removal was 73% forHRAP A, and 57% for HRAP B. Higher removal in HRAP Awas due to a lower inorganic nitrogen concentration inits effluent. Significant differences (p> 0.05) inthe relative proportions of nitrogen forms between thetwo HRAPs were observed only in autumn and winter.This was mainly because HRAP B did not achieve a highlevel of NH₄ ⁺-N removal by stripping andalgal uptake, as observed in HRAP A. NH₄ ⁺-Nstripping was the most important mechanism fornitrogen removal (mean efficiency of 47% and 32% inHRAP A and B, respectively) followed by algal uptake,and subsequent algal separation in the clarifiers(mean efficiency of 26% and 25% in HRAP A and Brespectively). The conclusion of this study is thatHRT determines both the nitrogen removal efficiencyand the distribution of nitrogen forms in the effluentof a HRAP. The nitrogen removal level can becontrolled through suitable HRT operating strategies.By operating at a HRT of 4 days in spring and summer,and 10 days in autumn and winter, nitrogenconcentration in the effluent of a HRAP system can bereduced to less than 15 mg L^-1 N.     

Separation of components of the biomass from high rate algal ponds using PercollR density gradient centrifugation

The biomass of a High Rate Algal Pond was separated into individual components of algae, bacteria and detritus. The two stage technique involved mechanical and chemical disaggregation of concentrated pond samples, followed by separation on preformed Percoll^R/sucrose density gradients. Throughout a diurnal cycle, monitored in September 1990, between 85 and 90% of the total chlorophylla was recovered in the algal fraction. The greatest loss of chlorophyll from the sample occurred during the concentration stage; no further losses were encountered during physical and chemical disaggregation. The technique enabled the direct gravimetric determination of the separated algal biomass. The potential applications of the technique are discussed.     

Seasonal productivity of a periphytic algal community for biofuel feedstock generation and nutrient treatment

Algal biomass is a promising feedstock for biofuel production. With a high lipid content and high rate of production, algae can produce more oil on less land than traditional bioenergy crops. Algal communities can also be used to remove nutrients from impacted waters. The purpose of this study was to demonstrate the ability of an algal turf scrubber (ATS)™ to facilitate the growth of periphytic algal communities for the production of biomass feedstock and the removal of nutrients from a local stream. A pilot-scale ATS was implemented in Springdale, AR, and operated over the course of a nine-month sampling period. System productivity over the nine-month operating time averaged 26 g m⁻² d⁻¹. Total phosphorus and total nitrogen removal averaged 48% and 13%, respectively. The system showed potential for biomass generation and nutrient removal across three seasons.     

Mini-review: high rate algal ponds,flexible systems for sustainable wastewater treatment

Over the last 20 years, there has been a growing requirement by governments around the world for organisations to adopt more sustainable practices. Wastewater treatment is no exception, with many currently used systems requiring large capital investment, land area and power consumption. High rate algal ponds offer a sustainable, efficient and lower cost option to the systems currently in use. They are shallow, mixed lagoon based systems, which aim to maximise wastewater treatment by creating optimal conditions for algal growth and oxygen production—the key processes which remove nitrogen and organic waste in HRAP systems. This design means they can treat wastewater to an acceptable quality within a fifth of time of other lagoon systems while using 50% less surface area. This smaller land requirement decreases both the construction costs and evaporative water losses, making larger volumes of treated water available for beneficial reuse. They are ideal for rural, peri-urban and remote communities as they require minimum power and little on-site management. This review will address the history of and current trends in high rate algal pond development and application; a comparison of their performance with other systems when treating various wastewaters; and discuss their potential for production of added-value products. Finally, the review will consider areas requiring further research.     

Cell identification and sizing using digital image analysis for estimation of cell biomass in High Rate Algal Ponds

Current environmental concerns make estimation of microbial biomass apriority for monitoring purposes and to advance scientific understanding. Thispaper considers problems associated with algal cell imaging and measurement forcell biomass estimation in samples from high rate algal ponds. In a complexsystem, the only way of measuring microbial activity is to measure theindividual cells and estimate biovolumes. Accurate biomass determinationsdemanddirect microscopic counting and measurement of the sizes of individualmicrobialcells taken from known volumes of water. The system used for routinemeasurementat the laboratory where the images were generated, based on standard microscopeequipment, is only suitable for treatment of well dispersed specimens.Differential interference contrast (DIC) microscopy, on the other hand, offersthe best solution for optical enhancement of cell contrast, and produces animage with well defined edges, yet presents a great challenge to routine cellidentification by digital image analysis, owing to the bas-relief type imageproduced. The paper outlines several image analysis methods developedspecifically for this purpose, and presents illustrative results.     

Comparison of macroinvertebrate community structure and driving environmental factors in natural and wastewater treatment ponds

Eutrophication still continues to be an issue of major concern for the protection of water quality, and accordingly, the European Union Water Framework Directive has set a minimum target for all waters where “good status” is defined as a slight departure from the biological community which would be expected in conditions of minimal anthropogenic impact. The use of constructed ponds for wastewater treatment aimed at achieving this target has shown to be an effective alternative to conventional systems in the farm landscape. Their applicability in these areas is of great interest since these ponds have the added potential to combine their wastewater treatment properties with that of biodiversity enhancement. This article focuses on exploring the community structure of both natural and constructed ponds used for wastewater treatment and the driving environmental factors. A total of 15 constructed and 5 natural ponds were sampled for aquatic macroinvertebrates and hydrochemistry in spring and summer 2006. Results showed that the most important factors responsible for the differences in the community structure between these two types of ponds were pH, vegetation structure and pollution levels. These gradients helped to structure a large proportion of the communities with some taxa being associated with the constructed ponds. These results highlight the potential contribution of constructed ponds used for wastewater treatment to the landscape biodiversity. The present findings also open the possibility for a more integrated management of water quality and biodiversity enhancement in farmland areas. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users. Guest editors: B. Oertli, R. Cereghino, A. Hull & R. Miracle Pond Conservation: From Science to Practice. 3rd Conference of the European Pond Conservation Network, Valencia, Spain, 14–16 May 2008     

An economic assessment of algal turf scrubber technology for treatment of dairy manure effluent

Controlling the input of nitrogen (N) and phosphorus (P) from dairies and other livestock operations into the surrounding air- and water-sheds poses both technical and economic challenges to the agricultural community. The purpose of this paper is to assess the economics of algal turf scrubber treatment technology at the farm-scale for a hypothetical 1000-cow dairy. Costs were developed for farms with and without anaerobic pretreatment. The majority of capital costs were due to land preparation, installation of liner material, and engineering fees. The majority of operational costs were due to energy requirements for biomass drying, pumping water, and repayment of capital investment. On farms using anaerobic pretreatment, waste heat from burning of biogas could be used to offset the energy requirements of biomass drying. In addition, biogas combustion exhaust gas could then be recycled back to the algal system to supply dissolved inorganic carbon for optimal algal production and pH control. Under the best case (algal system coupled with anaerobic digestion pretreatment), the yearly operational costs per cow, per kg N, per kg P, and per kg of dried biomass were $454, $6.20, $31.10, and $0.70, respectively. Without anaerobic digestion pretreatment, the yearly operational costs were 36% higher, amounting to $631 per cow, $8.70 per kg N, $43.20 per kg P, and $0.97 per kg of dried biomass. For perspective, a recent survey of 36 Maryland dairy farms found long-term annual profits of about $500 per cow. As no market currently exists for manure grown algal biomass, our cost analysis does not include any value of the biomass generated during manure treatment. In addition, there are a variety of potential uses for the algal biomass from manure treatment that could defray treatment costs. Future opportunities for dairies to participate in nutrient trading approaches to watershed nutrient management may also become important.     

Production and harvesting of microalgae for wastewater treatment, biofuels, and bioproducts

The integration of microalgae-based biofuel and bioproducts production with wastewater treatment has major advantages for both industries. However, major challenges to the implementation of an integrated system include the large-scale production of algae and the harvesting of microalgae in a way that allows for downstream processing to produce biofuels and other bioproducts of value. Although the majority of algal production systems use suspended cultures in either open ponds or closed reactors, the use of attached cultures may offer several advantages. With regard to harvesting methods, better understanding and control of autoflocculation and bioflocculation could improve performance and reduce chemical addition requirements for conventional mechanical methods that include centrifugation, tangential filtration, gravity sedimentation, and dissolved air flotation. There are many approaches currently used by companies and industries using clean water at laboratory, bench, and pilot scale; however, large-scale systems for controlled algae production and/or harvesting for wastewater treatment and subsequent processing for bioproducts are lacking. Further investigation and development of large-scale production and harvesting methods for biofuels and bioproducts are necessary, particularly with less studied but promising approaches such as those involving attached algal biofilm cultures.     

铝合金轮毂生产废水处理系统的设计和运行

某汽车零部件有限公司年产汽车铝合金轮毂200万只,每天产生酸性废水80m³、碱性废水524m³、含锌含铜废水181m³、含铬废水48m³和含镍废水40m³,生产废水总产生量为873m³·d^-1。废水总镍、总锌、总铬、总铜、pH、氟化物和COD的变化范围分别是5.34~18.72mg·L^-1、50.11~97.63mg·L^-1、2.66~16.21mg·L^-1、1.50~11.36mg·L^-1、5.2~8.4、5.0~17.4mg·L^-1、80.9~161.9mg·L^-1。铝合金轮毂生产废水处理系统设计水量为1052m³·d^-1,每个处理周期的运行时间为20h,系统运行稳定,连续30d出水均能达到广东省地方标准《水污染物排放限值》(DB44/26-2001)第二时段二级标准。     

Using secondary outcome to sharpen bounds for treatment harm rate in characterizing heterogeneity

In a clinical trial, statistical reports are typically concerned about the mean difference in two groups. Now there is increasing interest in the heterogeneity of the treatment effect, which has important implications in treatment evaluation and selection. The treatment harm rate (THR), which is defined by the proportion of people who has a worse outcome on the treatment compared to the control, was used to characterize the heterogeneity. Since THR involves the joint distribution of the two potential outcomes, it cannot be identified without further assumptions even in the randomized trials. We can only derive the simple bounds with the observed data. But the simple bounds are usually too wide. In this paper, we use a secondary outcome that satisfies the monotonicity assumption to tighten the bounds. It is shown that the bounds we derive cannot be wider than the simple bounds. We also construct some simulation studies to assess the performance of our bounds in finite sample. The results show that a secondary outcome, which is more closely related to the primary outcome, can lead to narrower bounds. Finally, we illustrate the application of the proposed bounds in a randomized clinical trial of determining whether the intensive glycemia could reduce the risk of development or progression of diabetic retinopathy.     

The necessity for low temperature treatment on the eggs of Emma Cricket,Teleogryllus emma and the method of increasing the hatching rate after low temperature treatment

The necessity for low temperature treatment of Emma Cricket Eggs, Teleogryllus emma, to dormancy breaking and the method of increasing hatching rate after low temperature treatment were investigated. Emma Cricket Eggs were treated by constant temperature, room temperature, low temperature, step‐down low temperature. As a result, constant temperature treatment was the lowest on hatching rate. The hatching rates of the rest of other temperature treatments were not different statistically (one‐way ANOVA). In other word, low temperature treatment was not necessary to dormancy breaking. But low temperature treatment was necessary to control individual number of Emma Cricket, Teleogryllus emma, on the mass indoor‐rearing system. And the step‐up temperature treatment was necessary to increase hatching rate after low temperature treatment.     

A cure‐rate model for Q‐learning: Estimating an adaptive immunosuppressant treatment strategy for allogeneic hematopoietic cell transplant patients

Cancers treated by transplantation are often curative, but immunosuppressive drugs are required to prevent and (if needed) to treat graft‐versus‐host disease. Estimation of an optimal adaptive treatment strategy when treatment at either one of two stages of treatment may lead to a cure has not yet been considered. Using a sample of 9563 patients treated for blood and bone cancers by allogeneic hematopoietic cell transplantation drawn from the Center for Blood and Marrow Transplant Research database, we provide a case study of a novel approach to Q‐learning for survival data in the presence of a potentially curative treatment, and demonstrate the results differ substantially from an implementation of Q‐learning that fails to account for the cure‐rate.     

Comparison of 7-day and 14-day proton pump inhibitor-containing triple therapy for Helicobacter pylori eradication: neither treatment duration provides acceptable eradication rate in Korea

BACKGROUND AND AIMS: Although triple combination therapy containing a proton pump inhibitor (PPI) and two antibiotics is considered as a standard regimen for the first-line anti-Helicobacter pylori treatment, there are still debates on the ideal duration of treatment. The aim of this study was to compare the efficacies of 7-day and 14-day PPI-containing triple therapy. MATERIALS AND METHODS: This study was performed in a randomized, multicenter, prospective manner. After upper gastrointestinal endoscopy, H. pylori-infected patients with a gastric ulcer and/or a duodenal ulcer were randomly assigned to a PAC7 group (omeprazole 20 mg or equivalent dose of other PPIs, amoxicillin 1000 mg, and clarithromycin 500 mg twice daily for 7 days) or to a PAC14 group (the same regimen as the PAC7 group but for 14 days). H. pylori status was evaluated by (13)C urea breath test 5 weeks after anti-ulcer treatment completion. RESULTS: A total of 598 patients were enrolled; 337 were randomized to the PAC7 group and 261 to the PAC14 group. The two groups were comparable in terms of baseline characteristics. The eradication rates of the PAC7 group were not inferior to those of the PAC14 group in both intention-to-treat analysis (71.2% vs. 75.5%) and per-protocol analysis (83.6% vs. 86.6%). Incidences of adverse events were comparable. CONCLUSIONS: Although the 7-day PPI-containing triple anti-H. pylori therapy is not inferior to the 14-day therapy, neither treatment duration provides acceptable eradication rate reaching 90% in per-protocol analysis. New combination regimen with higher efficacy should be developed as a first-line eradication therapy for H. pylori in Korea.     

Alginate from the macroalgae <Emphasis Type="Bold">Sargassum sinicola</Emphasis> as a novel source for microbial immobilization material in wastewater treatment and plant growth promotion

Alginate extracted from the macroalgae Sargassum sinicola was used as the raw material for co-immobilization of the microalgae Chlorella sorokiniana and growth-promoting bacterium Azospirillum brasilense for wastewater treatment and as an inoculant carrier of A. brasilense for plant growth promotion. The composition, structure, viscosity, color, and phenolic compound content of the alginate were analyzed and compared with commercially available alginate produced from the macroalgae Macrocystis pyrifera. From ¹H NMR analysis of alginate, S. sinicola was found to have more guluronic acid (F _G=0.64) than it had mannuronic acid (F _M=0.38) and had a viscosity of 13.5 m Pa s compared to 50 m Pa s for M. pyrifera. The S. sinicola alginate had dark brown color, reducing light penetration, with more phenolic compounds than M. pyrifera alginate. Nonetheless, growth of C. sorokiniana and A. brasilense in S. sinicola alginate was not significantly different than the growth in M. pyrifera alginate beads. Nutrient removal from wastewater by the co-immobilized microorganisms was similar for both types of alginate beads, and so was the growth enhancement of tomato plants inoculated with microbeads containing A. brasilense. This study shows the potential use of S. sinicola alginate as a raw material for cell immobilization for wastewater treatment and plant growth promotion.