Improvement of nutrients removal from domestic wastewater by activated-sludge encapsulation with polyvinyl alcohol (PVA).

Conventional activated-sludge (AS) technologies are deficient for nutrient removal because they require specific floc characteristics. Therefore, the encapsulated AS with polyvinyl alcohol (PVA) will favor floc's formation that removes nutrients. The applied method was based on monitoring the removal of organic matter and nutrients (NH4+, NO3-, NO2-, PO43-) from synthetic domestic wastewater using laboratory-scale AS. The experimental reactors were operated at 8 h as optimized Hydraulic Retention Time (HRT). The sludge characteristics evaluation was carried out through the Sludge Volumetric Index (SVI), Food/Microorganism ratio (F/M), and Mixed Liquor Volatile Suspended Solids (MLVSS). Other specific floc characteristics, such as zeta potential and effective diameter were also evaluated. The results showed that the encapsulated AS with PVA favors nitrogen and phosphorous removal up to 35% but it did not improve organic matter removal. In addition, encapsulated AS with PVA has the characteristics of filamentous sludge (F/M: 0.7 g COD g-1 MLVSS d-1) with good settleability conditions (SVI: 43 mL g-1 MLSVS h-1) and low zeta potential (ZP: -0.9 mV), which favors its separation from the liquid phase. In conclusion, the encapsulation of AS with PVA improves nutrient removal by improving floc characteristics.

Biorefinery of cellulosic primary sludge towards targeted Short Chain Fatty Acids, phosphorus and methane recovery.

Cellulose from used toilet paper is a major untapped resource embedded in municipal wastewater which recovery and valorization to valuable products can be optimized. Cellulosic primary sludge (CPS) can be separated by upstream dynamic sieving and anaerobically digested to recover methane as much as 4.02 m3/capita·year. On the other hand, optimal acidogenic fermenting conditions of CPS allows the production of targeted short-chain fatty acids (SCFAs) as much as 2.92 kg COD/capita·year. Here propionate content can be more than 30% and can optimize the enhanced biological phosphorus removal (EBPR) processes or the higher valuable co-polymer of polyhydroxyalkanoates (PHAs). In this work, first a full set of batch assays were used at three different temperatures (37, 55 and 70 °C) and three different initial pH (8, 9 and 10) to identify the best conditions for optimizing both the total SCFAs and propionate content from CPS fermentation. Then, the optimal conditions were applied in long term to a Sequencing Batch Fermentation Reactor where the highest propionate production (100-120 mg COD/g TVSfed·d) was obtained at 37 °C and adjusting the feeding pH at 8. This was attributed to the higher hydrolysis efficiency of the cellulosic materials (up to 44%), which increased the selective growth of Propionibacterium acidopropionici in the fermentation broth up to 34%. At the same time, around 88% of the phosphorus released during the acidogenic fermentation was recovered as much as 0.15 kg of struvite per capita·year. Finally, the potential market value was preliminary estimated for the recovered materials that can triple over the conventional scenario of biogas recovery in existing municipal wastewater treatment plants.

Extracellular enzymatic activity of two hydrolases in wastewater treatment for biological nutrient removal.

Due to the complex nature of the wastewater (both domestic and non-domestic) composition, biological processes are widely used to remove nutrients, such as carbon (C), nitrogen (N), and phosphorous (P), which cause instability and hence contribute to the damage of water bodies. Systems with different configurations have been developed (including anaerobic, anoxic, and aerobic conditions) for the joint removal of carbon, nitrogen, and phosphorus. The goal of this research is to evaluate the extracellular activity of ß-glucosidase and phosphatase enzymes in a University of Cape Town (UCT) system fed with two synthetic wastewaters of different molecular complexity. Both types of waters have medium strength characteristics similar to those of domestic wastewater with a mean C/N/P ratio of 100:13:1. The operation parameters were hydraulic retention time (HRT) of 10 h, solid retention time (SRT) of 12 days, mean concentration of the influent in terms of chemical oxygen demand (COD), total Kjeldahl nitrogen (TKN), and total phosphorus (TP) of 600, 80, and 6 mg/L, respectively. According to the results obtained, statistically significant differences have been found in the extracellular enzyme activities with the evaluated wastewaters and in the units comprising the treatment system in some of the cases. An analysis of principal components showed that the extracellular enzymatic activity has been correlated to nutrient concentration in wastewater, biomass concentration in the system, and metabolic conditions of treatment phases. Additionally, this research has allowed determining an inverse relationship between wastewater biodegradability and the extracellular enzyme activity of ß-glucosidase and phosphatase. These results highlight the importance of including the analysis of biomass biochemical characteristics as control methods in wastewater treatment systems for the nutrient removal.

Effect of solids retention time on nitrogen and phosphorus removal from municipal wastewater in a sequencing batch membrane bioreactor.

This study evaluated the removal of organic matter, nitrogen and phosphate from a municipal wastewater in a sequencing batch membrane bioreactor (SBMBR) operated at different solids retention times (SRTs) and subjected to different aeration profiles. The results demonstrated that SRT reduction from 80 to 20 d had a negligible effect on chemical oxygen demand (COD) removal and only a slight negative effect on nitrification. COD removal efficiency remained stable at 97%, whereas ammonium removal decreased from 99% to 97%. The total nitrogen removal efficiency was improved by SRT reduction, increasing from 80% to 86%. Although the total phosphorus (TP) removal was not significantly affected by the SRT reduction, ranging from 40-49%, the P-release and P-uptake processes were observed to increase as the SRT was reduced. The implementation of a pre-aeration phase in the SBMBR operating cycle allowed a higher TP removal performance, which reached up to 76%. Batch tests suggested that the fraction of phosphate removed anoxically from the total (anoxic + aerobic) phosphate removal decreased with the SRT reduction.

Enhancement of nutrient removal from swine wastewater digestate coupled to biogas purification by microalgae Scenedesmus spp.

This work investigated the effects of swine wastewater-derived biogas on microalgae biomass production and nutrient removal rates from piggery wastewater concomitantly with biogas filtration. Photobioreactors with dominant Scenedesmus spp. were prepared using non-sterile digestate and exposed to different photoperiods. In the presence of biogas and autotrophic conditions microalgae yield of 1.1±0.2 g L(-1) (growth rate of 141.8±3.5 mg L(-1) d(-1)) was obtained leading to faster N-NH3 and P-PO4(3-) assimilation rate of 21.2±1.2 and 3.5±2.5 mg L(-1) d(-1), respectively. H2S up to 3000 ppmv was not inhibitory and completely removed. Maximum CO2 assimilation of 219±4.8 mg L(-1) d(-1) was achieved. Biological consumption of CH4 up to 18% v/v was verified. O2 up to 22% v/v was controlled by adding acetate to exacerbate oxygen demand by microorganisms. Microalgae-based wastewater treatment coupled to biogas purification accelerates nutrient removal concomitantly producing valuable biomass and biomethane.

Mineral composition of the sugarcane juice and its influence on the ethanol fermentation.

In the present work, we evaluated the mineral composition of three sugarcane varieties from different areas in northeast Brazil and their influence on the fermentation performance of Saccharomyces cerevisiae. The mineral composition was homogeneous in the different areas investigated. However, large variation coefficients were observed for concentrations of copper, magnesium, zinc and phosphorus. Regarding the fermentation performances, the sugarcane juices with the highest magnesium concentration showed the highest ethanol yield. Synthetic media supplemented with magnesium also showed the highest yield (0.45 g g(-1)) while the excess of copper led to the lowest yield (0.35 g g(-1)). According to our results, the magnesium is the principal responsible for the increase on the ethanol yield, and it also seems to be able to disguise the inhibitory effects of the toxic minerals present in the sugarcane juice.

Supercritical water gasification of sewage sludge: gas production and phosphorus recovery.

In this study, the feasibility of the gasification of dewatered sewage sludge in supercritical water (SCW) for energy recovery combined with P-recovery from the solid residue generated in this process was investigated. SCWG temperature (400°C, 500°C, 600°C) and residence time (15min, 30min, 60min) were varied to investigate their effects on gas production and the P recovery by acid leaching. The results show that the dry gas composition for this uncatalyzed gasification of sewage sludge in SCW mainly comprised of CO2, CO, CH4, H2, and some C2-C3 compounds. Higher temperatures and longer residence times favored the production of H2 and CH4. After SCWG, more than 95% of the P could be recovered from the solid residue by leaching with acids. SCWG combined with acid leaching seems an effective method for both energy recovery and high P recovery from sewage sludge.

Mineralización y/o solubilización del fósforo contenido en lodos provenientes de residuos salmonícolas marinos bioaumentados con cepas de aspergillus niger Y trichoederma pseudokoningi / Mineralization and/or solubilization phosphorus content from salmon waste sludge marine bioincreased with strains aspergillus niger and trichoederma pseudokoningi

Se evaluó un lodo salmonícola, proveniente de centros de cultivo marinos, con el objetivo de evaluar el aumento en la mineralización y/o solubilización del fósforo del lodo salmonícola tratado con la inoculación de cepas chilenas de hongos. El lodo fue pretratado mediante esterilización, pasteurización y sin pretratar. Posteriormente, fue inoculado con cepas nativas de Aspergillus niger y Trichoderma pseudokoningii, usando dos controles: sin adición de inóculo y otro, con la cepa control A. niger ANC. Estas muestras fueron incubadas por 60 días, determinándose el pH y la disponibilidad de fósforo (P) en los lodos pretratados. Luego de esta primera fase, las muestras fueron incubadas en tubos de lixiviación a temperatura controlada durante 6 semanas evaluando la cinética de mineralización de P de los lodos. Los pretratamientos aplicados al lodo aumentaron la disponibilidad de P con la disminución del pH. La esterilización del lodo influyó en la colonización microbial, presentando la mayor colonización de las cepas inoculadas y la mayor liberación de P a la solución. El pretratamiento de esterilización inoculado con la cepa control A. niger presentó el mayor potencial de mineralización de P, siendo significativamente mayor a las cepas nativas y al control evaluado.

A salmon sludge from marine farming centers was evaluated with the aim to increase the mineralization and/or solubilization of their phosphorus (P) content through the inoculation of Chilean fungi strains. The sludge was pretreated through sterilization, pasteurization and without any pretreatment. After were inoculated with native strains of Aspergillus niger and Trichoderma pseudokoningii, using two controls: without inoculum and with inoculation with A. niger ANC. The samples were incubated for 60 days at room temperature and pH and P availability was determined. After this first phase, the samples were additionally incubated for other 6 weeks, in leaching tubes, at controlled temperature (25 ºC) evaluating the sludge kinetics of P mineralization. The pretreatment applied to the sludge increased P availability with a pH value decline. The sludge sterilization had an influence on the microbial colonization, presenting high colonization of the inoculated strains and more P was available. The pretreatment of sterilization inoculated with the control strain A. niger presented the biggest potential for mineralization of P, being significantly higher than the native strains and control evaluated in this study.

Spatial distribution and temporal variability of ammonium-nitrogen, phosphorus, and potassium in a rice field in Corrientes, Argentina.

Proper and effective management of soil nutrients requires assessment of their variability at the field scale. We compare the effects of lime amendment rate on the spatial variability of three macronutrient forms (NH4 (+)-N, Olsen P, and Mehlich-1 K) in a paddy soil at three different dates during the growth period of a rice crop. The field work was carried out near Corrientes, Argentina. Lime treatments were 0, 625, and 1250 kg ha(-1) dolomite, and each liming dose was applied to a 1.7 ha field. Ninety-three soil samples per treatment were first collected in aerobic conditions and then two more times after flooding, at bunch formation and flowering. Soil NH4 (+)-N increased along time, whereas P was highest at bunch formation and K steadily decreased along the rice growth period. Dolomite addition increased macronutrient availability at the first and second samplings, but its effects at the third sampling depended on the element. The three soil nutrients analyzed displayed strong patterns of spatial dependence for the three lime treatments and at the three periods studied. The areas with relative high or low macronutrient concentrations within each field were not stable throughout the rice growth period. Seasonality in the spatial distribution of macronutrients may be of agronomic value for site specific management.

Chemical phosphorus removal: a clean strategy for piggery wastewater management in Brazil.

The intensive production of animal protein is known to be an environmental polluting activity, especially if the wastewater produced is not managed properly. Swine production in Brazil is growing, and technologies to manage all pollutants present in the wastewater effluent are needed. This work presents a case of study of phosphorus (P) removal from piggery wastewater using Ca(OH)2, and demonstrates the feasibility of this strategy for P management. The effluent of a swine manure treatment plant was treated with Ca(OH)2. According to the addition of Ca(OH)2 the pH of the effluent ranged from 8.0 to 10.0. Different conditions of sludge dewatering were evaluated, and the chemical composition of sludge was investigated. Ion chromatography analysis of effluent samples showed that 92% of total P (TP) was present as soluble P (SP) whereas 75% of SP species were present as phosphate. The efficiency of P removal was typically 90% at pH 8.5 and higher than 98% at pH 10.5. The sludge was separated by sedimentation, centrifugation or filtration and dried. The TP content of dried sludge was 9.3% (w/w). X-ray diffraction analysis of the dry sludge showed the presence of amorphous compounds of Ca and P, which is an indication that the sludge obtained from the swine manure treatment has a potential for application as biofertilizer.

High nutrient removal rate from swine wastes and protein biomass production by full-scale duckweed ponds.

Duckweed ponds have been successfully used in swine waste polishing, generating a biomass with high protein content. Therefore, the present study evaluated the efficiency of two full-scale duckweed ponds considering nutrient recovery from a piggery farm effluent (produced by 300 animals), as well as the biomass yield and crude protein (CP) content. A significant improvement in the effluent quality was observed, with the removal of 98.0% of the TKN (Total Kjeldahl Nitrogen) and 98.8% of the TP (Total Phosphorous), on average. The observed nitrogen removal rate is one of the highest reported (4.4 g/m(2)day of TKN). Additionally, the dissolved oxygen level rose from 0.0 to 3.0mg/L, on average. The two ponds together produced over 13 tons of biomass (68 t/ha year of dry biomass), with 35% crude protein content. Because of the excellent nutrient removal and protein biomass production, the duckweed ponds revealed a great potential for the polishing and valorisation of swine waste, under the presented conditions.

Nitrogen and phosphorus removal using a novel integrated system of natural zeolite and lime.

Nitrogen and phosphorus can cause eutrophication problems in receiving waters. These nutrients can be eliminated by different wastewater treatments but they tend to be costly or require complex operations. With these reasons in mind, this work set out to study the behavior of a novel combined or integrated system with zeolite and lime for the removal of these chemical species. With the integrated treatment, excellent removals-98 % NH(+) (4), 100 % total phosphorus (TP), 79 % chemical oxygen demand (COD), 71 % BOD(5), 99 % of total suspended solids (TSS) and 100 % of fecal coliforms-were obtained. A sludge production of 4.4 % and 4.8 % of the wastewater total volume treated with lime was achieved. The final liquid effluent of the integrated system of natural zeolite and lime had a composition which was suitable for its discharge into sewerage systems and marine or continental waters (according to Chilean regulations), as far as the concentrations of nitrogen, phosphorus and total coliforms were concerned. Validated curves with their corresponding equations were obtained in this study for the removal of ammonia nitrogen and total phosphorus. These equations can theoretically be applied to estimate the removal of both parameters in studies or practical applications undertaken with operating conditions similar to those used in this work.

Seeking a way to promote the use of constructed wetlands for domestic wastewater treatment in developing countries.

The aim of this study was to evaluate the domestic wastewater treatment efficiency as well as the survivability of commercially valuable ornamental plants in subsurface flow wetlands (SSFW) for domestic wastewater (DWW) treatment in laboratory and pilot wetland studies. The laboratory scale study included five different species (Zantedeschia aethiopica, Strelitzia reginae, Anthurium andreanum, Canna hybrids and Hemmerocallis dumortieri) that were evaluated in horizontal flow subsurface treatment cells. All the plants survived during the 6-month experimental period demonstrating high wetland nutrient treatment efficiency. In order to validate and expand these preliminary results, a pilot-scale wetland study was carried out in SSFWs under two different flow regimes (horizontal and vertical flow). Four ornamental species were tested during a 1-year period: Zantedeschia aethiopica, Strelitzia reginae, Anthurium andreanum and Agapanthus africanus. The removal efficiencies were significantly higher in the vertical subsurface-flow constructed wetlands (VFCW) for all pollutants, except for nitrate (NO(3)-N), total nitrogen (TN) and total suspended solids (TSS). These results show that it is feasible to use select non-wetland plants with high market value in SSFWs without reducing the efficiency of the wastewater treatment system, although future work should continue in order to apply this technology in a large scale. The added value of floriculture in treatment wetlands can help to promote the use of constructed wetlands (CW) for domestic wastewater treatment in developing countries where economical resources are scarce and water pollution with DWW is common.

Phosphorous removal in batch systems using ferric chloride in the presence of activated sludges.

The objectives of this work were: (a) to analyze the effect of alkalinity, pH and initial Fe:P molar ratio (Fe(0):P(0)) on the precipitation of orthophosphate using ferric chloride in the presence of activated sludge in order to represent conditions of simultaneous precipitation, and in exhausted wastewater to simulate conditions of post-precipitation, (b) to compare the experimental results with predictions obtained from a chemical equilibrium model, and (c) to propose a mechanistic model to determine the dose of coagulant required to achieve a given orthophosphate removal degree at constant pH. Results showed that the presence of biomass did not affect the orthophosphate precipitation; however, addition of ferric chloride caused a drop of pH to values not compatible with the normal activity of activated sludges. For this reason, the wastewater was supplemented with NaHCO(3); when 1gL(-1) NaHCO(3) was added, orthophosphate removals higher than 97% and pH above 6.2 were obtained using Fe(0):P(0)=1.9. Precipitation assays at constant pH showed that Fe(III) hydrolysis and FePO(4) precipitation reaction compete with each other. Calculations using a chemical equilibrium model (CHEAQS) predicted that ferric phosphate precipitation should not take place if pH is higher than about 7.8. However, experimental results showed that ferric phosphate precipitation occurred even at pH 9. For this reason, a mechanistic model was proposed to predict orthophosphate concentrations as a function of Fe(0):P(0) at constant pH. The model can be applied to calculate the minimum Fe(III) concentration required to achieve a given discharge limit for orthophosphate as a function of its initial concentration and pH.

Growth and nutrient removal in free and immobilized green algae in batch and semi-continuous cultures treating real wastewater.

Two species of microalgae growing as immobilized and free-cells were compared to test its ability to remove N and P in batch cultures of urban wastewater. The best microalgae-cell growth configuration was selected to be tested in bioreactor operated in semi-continuous mode. Scenedesmus obliquus showed a higher N and P uptake rate in urban wastewater than Chlorella vulgaris. When tested in semi-continuous mode and with the re-calcification of beads, S. obliquus was more effective in removing N and P for longer periods (181 h) than batch cultures; fecal coliforms removal was good (95%) although the final concentration was still unsuitable for discharge to natural water bodies. Protein and lipids content analysis suggest that, from a practical point of view, immobilized systems could facilitate the separation of the biomass from the treated wastewater although in terms of nutritional value of the biomass, immobilized systems do not represent an advantage over free-cell systems.

Combined treatment of leachate from sanitary landfill and municipal wastewater by UASB reactors.

Landfills are among the most affordable and acceptable methods in terms of public health and environmental protection for the final disposal of solid waste. Leachate treatment incorporated into anaerobic domestic wastewater systems could be a viable and efficient alternative which would allow minimizing implementation and operation costs of the landfill, to reduce requirements of chemical inputs such as pH conditioners and phosphorus supply. This study showed the potential of anaerobic treatment in an UASB reactor treating a combination of domestic wastewater and leachate in a 5% volumetric ratio of leachate. Under these conditions the reactor assimilated properly the leachate fraction incorporated. With a HRT of 8 h and a mean volumetric organic load of 2.84 kg m(-3) d(-1) COD removal efficiencies around 70% were obtained, without inhibition problems; however, the necessity of a complementary treatment for improving carbonaceous and nitrogenous organic matter reduction is evident.

Comparative performance evaluation of full-scale anaerobic and aerobic wastewater treatment processes in Brazil.

This article evaluates and compares the actual behavior of 166 full-scale anaerobic and aerobic wastewater treatment plants in operation in Brazil, providing information on the performance of the processes in terms of the quality of the generated effluent and the removal efficiency achieved. The observed results of effluent concentrations and removal efficiencies of the constituents BOD, COD, TSS (total suspended solids), TN (total nitrogen), TP (total phosphorus) and FC (faecal or thermotolerant coliforms) have been compared with the typical expected performance reported in the literature. The treatment technologies selected for study were: (a) predominantly anaerobic: (i) septic tank + anaerobic filter (ST + AF), (ii) UASB reactor without post-treatment (UASB) and (iii) UASB reactor followed by several post-treatment processes (UASB + POST); (b) predominantly aerobic: (iv) facultative pond (FP), (v) anaerobic pond followed by facultative pond (AP + FP) and (vi) activated sludge (AS). The results, confirmed by statistical tests, showed that, in general, the best performance was achieved by AS, but closely followed by UASB reactor, when operating with any kind of post-treatment. The effluent quality of the anaerobic processes ST + AF and UASB reactor without post-treatment was very similar to the one presented by facultative pond, a simpler aerobic process, regarding organic matter.

Performance evaluation of a simple wastewater treatment system comprised by UASB reactor, shallow polishing ponds and coarse rock filter.

The work investigates a small full-scale wastewater treatment system comprised by the following units in series: UASB reactor, three polishing ponds and one coarse rock filter. The overall performance of the system is analyzed based on three years of monitoring using physical-chemical and biological parameters. Good organic matter, suspended solids and ammonia removal is achieved, together with excellent coliform removal (5.70 log units). Mean effluent concentrations of the main parameters are: BOD: 39 mg/L; COD: 109 mg/L; SS = 41 mg/L; ammonia: 10 mg/L; E. coli: 540 MPN/100 mL, indicating compliance with many regulations for effluent discharge and reuse. Main algal classes found in the ponds and final effluent were chlorophyta and euglenophyta. The system is completely unmechanized and has a relatively small total hydraulic retention time (less than 13 days), compared with most natural treatment processes. No sludge removal from the ponds and filter has been necessary so far.

Comparison of bioreactors with different kinds of submerged packed beds for domestic wastewater treatment.

The performance of aerobic submerged packed bed reactors was studied for the treatment of domestic wastewater using different kinds of packing materials with high specific areas (760-1,200 m(2)/m(3)). The tested materials were ceramic spheres, crushed tezontle, grains of high density polyethylene (HDPE), of low density polyethylene (LDPE) and of polypropylene (PP), cubes of polyurethane (PU) and polyethylene tape (SESSIL). The bioreactors were operated in continuous regime, applying organic loads in the range of 0.8-6.0 g COD.m(-2).d(-1). The obtained specific COD removal rates were very similar in all the reactors when they were operated at organic loads up to 2.0 g COD.m(-2).d(-1), after which differences in effectiveness appeared and the best results were determined in the reactors with SESSIL, LDPE and PU. Very low TSS, O&G and turbidity were obtained in all the effluents. The NH(3)-N and TN removals were dependent on the dissolved oxygen (DO) concentration and the removals at DO of 5 mg/l were 84-99% and 61-74% respectively. The best removals were determined in the reactors with PU, SESSIL and LDPE. The reactor with tezontle had also a good performance when operated with loads up to 1.0 g TN.m(-2).d(-1). The best phosphate removals (38-49%) were obtained in the reactors with PU, tezontle, ceramic sheres and SESSIL.

Differences in phosphorus and nitrogen delivery to the Gulf of Mexico from the Mississippi River Basin.

Seasonal hypoxia in the northern Gulf of Mexico has been linked to increased nitrogen fluxes from the Mississippi and Atchafalaya River Basins, though recent evidence shows that phosphorus also influences productivity in the Gulf. We developed a spatially explicit and structurally detailed SPARROW water-quality model that reveals important differences in the sources and transport processes that control nitrogen (N) and phosphorus (P) delivery to the Gulf. Our model simulations indicate that agricultural sources in the watersheds contribute more than 70% of the delivered N and P. However, corn and soybean cultivation is the largest contributor of N (52%), followed by atmospheric deposition sources (16%); whereas P originates primarily from animal manure on pasture and rangelands (37%), followed by corn and soybeans (25%), other crops (18%), and urban sources (12%). The fraction of in-stream P and N load delivered to the Gulf increases with stream size, but reservoir trapping of P causes large local- and regional-scale differences in delivery. Our results indicate the diversity of management approaches required to achieve efficient control of nutrient loads to the Gulf. These include recognition of important differences in the agricultural sources of N and P, the role of atmospheric N, attention to P sources downstream from reservoirs, and better control of both N and P in close proximity to large rivers.