Nutrient-rich Wastewater Research Articles

Turbulence measurements in a small subtropical estuary under king tide conditions

In natural waterways and estuaries, the understanding of turbulent mixing is critical to the knowledge of sediment transport, stormwater runoff during flood events, and release of nutrient-rich wastewater into ecosystems. In the present study, some field measurements were conducted in a small subtropical estuary with micro-tidal range and semi-diurnal tides during king tide conditions: i.e., the tidal range was the largest for both 2009 and 2010. The turbulent velocity measurements were performed continuously at high-frequency (50Hz) for 60 h. Two acoustic Doppler velocimeters (ADVs) were sampled simultaneously in the middle estuarine zone, and a third ADV was deployed in the upper estuary for 12 h only. The results provided an unique characterisation of the turbulence in both middle and upper estuarine zones under the king tide conditions. The present observations showed some marked differences between king tide and neap tide conditions. During the king tide conditions, the tidal forcing was the dominant water exchange and circulation mechanism in the estuary. In contrast, the long-term oscillations linked with internal and external resonance played a major role in the turbulent mixing during neap tides. The data set showed further that the upper estuarine zone was drastically less affected by the spring tide range: the flow motion remained slow, but the turbulent velocity data were affected by the propagation of a transient front during the very early flood tide motion at the sampling site.

Technical Note: Nutrient Removal from Swine Wastewater by Growing Duckweed: A Pilot Study

A pilot-scale duckweed pond was installed and integrated into the existing swine wastewater management system of a swine farm in Zebulon, North Carolina to investigate its effectiveness in removing nutrients from anaerobically treated swine wastewater. The nutrient-rich wastewater was added intermittently into the duckweed pond to maintain an ammonium (NH4-N) concentration of about 20 mg L-1, and the duckweed was harvested regularly to ultimately remove nutrients from the water body. The results show that duckweed (Spirodela polyrrhiza) grew rapidly on swine wastewater under field conditions, with a dry biomass yield of 10.7 g m-2 d-1 in August and September. Over the 16-week experimental period, NH4-N, the major nutrient concern in swine wastewater, was removed at 1.12 g m-2 d-1. The fast duckweed growth and an average duckweed protein content of 26.3% enabled a protein yield of 2.11 g m-2 d-1 throughout the experiment.

Simultaneous removal of heavy metals from phosphorous rich real wastewaters by micellar-enhanced ultrafiltration

In this study micellar-enhanced ultrafiltration (MEUF) was used to simultaneously remove heavy metals from phosphorous rich drainage waters of a fertilizer company, obtaining the purification of the nutrient rich wastewater. Response surface methodology approach was used to model and optimise the rejection coefficients of cadmium and copper. The factors studied were pH and SDS feed concentration. Results show that the removal of copper and cadmium was more efficient at low pH values. SDS feed concentration higher than 60mM was needed to obtain an efficient removal of cadmium and copper due to the competition of other metals present in the real drainage waters. The optimum rejection coefficients achieved were 84.3% and 75.0% for cadmium and copper, respectively, at the pH value of 3.2 and SDS feed concentration of 75.6mM. In addition, calculated rejection coefficients for zinc and nickel show that copper was the least trapped heavy metal and the MEUF removal efficiency was as follows, Zn=Ni>Cd>Cu. The flux decreased when increasing SDS feed concentration due to concentration polarisation, which was more significant above the SDS feed concentration of 60mM. Irreversible fouling was negligible in the whole set of experiments. Secondary pollution due to the SDS leakage to the permeate was also negligible.

Study on Shrimp Waste Water and Vermicompost as a Nutrient Source for Bell Peppers

The aquaculture industry generates significant nutrient-rich wastewater that is released into streams and rivers causing environmental concern. The objective of this controlled environment study was to evaluate the effect of waste shrimp water (SW), vermicompost (VC), at rates of 10%, 20%, 40%, and 80% by volume alone or in combination with SW, controlled-release fertilizer (CRF), and water-soluble fertilizer (WSF) on bell peppers (Capsicum annuum L.) cv. X3R Red Knight. Application of VC at 80% or SW alone increased yields relative to unfertilized control. Combined applications of VC and SW increased yields compared with VC alone. Overall, total yields were greatest in the chemical fertilizer treatments (CRF and WSF) and least in the unfertilized control. SW and VC increased growth medium pH relative to the unfertilized control or to the chemical fertilizer treatments. In pepper fruits, the greatest nitrogen (N) content was found in the CRF treatment, although it was not different from VC at high rates or WSF treatments. Phosphorus concentration in peppers was greatest in the CRF treatment, less in all VC or SW treatments, but not different from unfertilized control or WSF treatment. Iron, magnesium (Mg), and zinc concentrations in peppers were greatest in CRF treatment but not different from control or WSF treatments. Overall, N accumulation in peppers was negatively correlated to growth medium pH and calcium (Ca); phosphorus (P) in peppers was negatively correlated to growth medium pH, Ca, and sodium (Na), whereas potassium (K) in peppers was negatively correlated to growth medium P, Mg, and Na. Results indicated: 1) SW may not be a viable pepper nutrient source; (2) SW can provide a similar nutrient supply as VC; and (3) chemical fertilizers can provide higher pepper yields compared with SW or VC alone or in combination.

Growth Rate Kinetics for Struvite Crystallization

The crystallisation of struvite is one means of removing phosphate (and nitrogen) from nutrient-rich wastewater. As with all crystallisation processes, the growth rate of the crystals and its dependence on supersaturation is of considerable interest in designing processing equipment Modelling of struvite solubility using the computer package MINTEQA2 showed that struvite exhibits a minimum solubility in moderately alkaline conditions, with increasing solubility in acidic and strongly alkaline solutions, while temperature has only a minimal effect on struvite solubility. To measure the growth rate of struvite crystals, laboratory measurements were conducted in an isothermal batch I L stirred seeded crystallizer. Experiments were performed in aqueous solution at three pH levels (7.5, 8.0 and 8.5) and three temperatures (25, 35 and 40 degrees C) for similar initial ionic concentrations with phosphate being the limiting ion. These conditions were chosen to cover the pH values at which struvite readily crystallises without excessive adjustment of the wastewater pH, and at temperatures typical of many wastewaters. The increase in crystal size with time together with the decrease in the concentration of the ionic species in solution were followed. Rapid crystallisation kinetics were observed in the solution, with growth rates over 20 mu m/min at pH 8.5. A second order dependence of growth rate on supersaturation (as phosphate concentration) was observed, and the growth rate constant increased as pH increased but was insensitive to temperature over the range of conditions used. Results from a 200 L pilot-scale trial of struvite crystallisation at a local abattoir were consistent with the laboratory results.

A comparative study on the potential of oxygen release by roots of selected wetland plants

The capacity of root oxygen release by selected wetland plants pre-grown under both nutrient solution and artificial wastewater conditions were determined. The results indicated that the significant differences of root oxygen release by the tested wetland plants existed, and the biochemical process was the main source of root oxygen release as oxygen released by Vetiveria zizanioides L. Nash roots through biochemical process was contributed to 77% and 74% of total root oxygen release under nutrient solution conditions and artificial wastewater conditions, respectively, and that was 72% and 71% of total root oxygen release for Cyperus alternifolius L. It was found that the formation of root plaque with iron oxide was a function of root oxygen release as iron oxide concentration in root plaque was positively correlated to the potential of oxygen released by wetland plant roots with the regression coefficients as 0.874 *( p < 0.05) under nutrient solution conditions and 0.944 **( p < 0.01) under artificial wastewater conditions, which could be regarded as an important mechanism of wetland plants being tolerant to anoxia during wastewater treatment. It was suggested that the potential of root oxygen release could be used as a parameter for selecting wetland plants that can increase oxygen supply to soil or substrate of constructed wetlands and enhance nutrient transformation and removal, and V. zizanioides L. Nash with the highest potential of root oxygen release and higher tolerance to wastewater could be recommended to establish vegetated wetlands for treating nutrient-rich wastewater such as domestic wastewater.

From Waste to Superbrand: The Uneasy Relationship between Vegemite and Its Origins

From Waste to Superbrand: The Uneasy Relationship between Vegemite and Its Origins

Biological Nitrogen and COD Removal of Nutrient-Rich Wastewater Using Aerobic and Anaerobic Reactors

A preliminary study on nitrogen and organic removal efficiency of a lab-scale system using aerobic and an-aerobic reactors was performed. A simulated wastewater containing elevated levels of nitrogen was used. This paper aims to compare the efficiency of aerobic and anaerobic reactors in achieving nitrogen and chemical oxygen demand (COD) removal of nutrient-rich wastewater. It also presents the start-up experi-mentation conducted on simulated wastewater using two different reactors configured as aerobic and anaero-bic. Start-up experiments were carried out using a 5-liter acrylic aerobic reactor and a 4-liter flask anaerobic reactor containing activated sludge taken from De La Salle University (DLSU) wastewater treatment plant as a source of inoculum. Simulated wastewater was continuously fed to the two reactors and the time course of biomass growth was monitored by measuring the biomass concentration represented by mixed liquor volatile solids (MLVS). The time course of organic pollutant reduction by measuring the chemical oxygen demand (COD) was conducted until steady state condition was reached. On the other hand, COD and nitrogen tests such as Ammonia nitrogen (NH3-N), Nitrite nitrogen (NO2--N), Nitrate nitrogen (NO3--N) were also per-formed using 5 batch aerobic reactors containing different concentrations of wastewater and a single batch anaerobic reactor to see the effect of different feed concentrations in the removal of nitrogen. Preliminary results showed that 98% reduction in COD was obtained in aerobic reactor, as supported by increasing con-centration of MLVS, with a hydraulic retention time (HRT) of 5 hours after 11 days while 34% reduction in COD was obtained in anaerobic reactor with the same HRT after 14 days.

An approach of estimating struvite growth kinetic incorporating thermodynamic and solution chemistry, kinetic and process description

Discharge of untreated nutrient-rich wastewater is a problematic issue, which may cause root burning and the eutrophication of receiving water. It is also a problematic issue due to the formation of crystalline deposits in waste water systems. The recovery of nutrient using crystallization technique may provide a value added product. The recovered product is struvite, which is chemically known as magnesium ammonium phosphate hexahydrates. The key focus of this paper is the modeling and simulation of struvite growth, incorporating solution chemistry and thermodynamics, growth kinetic and process description of the recovery system. An ensemble of experimental data is combined with the dynamic model to estimate struvite growth kinetics.

Development of a 2-sludge, 3-stage system for nitrogen and phosphorous removal from nutrient-rich wastewater using granular sludge and biofilms

A novel 2-sludge 3-stage process using a combination of granular sludge and biofilm was developed to achieve biological removal of nitrogen and phosphorus from nutrient-rich wastewater. The system consists of a granular sequencing batch reactor (SBR) working under alternating anaerobic/anoxic conditions supplemented with a short aerobic phase and an aerobic biofilm SBR. The wastewater is first fed to the granular SBR reactor, where easily biodegradable carbon sources are taken up primarily by polyphosphate accumulating organisms (PAOs). The supernatant resulting from quick settling of the granular sludge is then fed to the biofilm SBR for nitrification, which produces oxidized nitrogen that is returned to the granular reactor for simultaneous denitrification and phosphorus removal. While maximizing the utilization of organic substrates and reducing operational costs, as do other 2-sludge processes previously reported in literature, the proposed system solves the bottleneck problem of traditional 2-sludge systems, namely high effluent ammonia concentration, due to its high-volume exchange ratios. An ammonia oxidation rate of 32 mg N/L h was achieved in the biofilm SBR, which produced nitrite as the final product. This nitrite stream was found to cause major inhibition on the anoxic P uptake and also to result in the accumulation of N 2O. These problems were solved by feeding the nitrite-containing stream continuously to the granular reactor in the anoxic phase. With a nitrogen and phosphorus removal efficiency of 81% and 94%, respectively, the system produces an effluent that is suitable for land irrigation from a wastewater stream containing 270 mg N/L of total nitrogen and 40 mg P/L of total phosphorus.

Performance of a water hyacinth (Eichhornia crassipes) system in the treatment of wastewater from a duck farm and the effects of using water hyacinth as duck feed

Nowadays, intensive breeding of poultry and livestock of large scale has made the treatment of its waste and wastewater an urgent environmental issue, which motivated this study. A wetland of 688 m2 was constructed on an egg duck farm, and water hyacinth (Eichhornia crassipes) was chosen as an aquatic plant for the wetland and used as food for duck production. The objectives of this study were to test the role of water hyacinth in purifying nutrient-rich wastewater and its effects on the ducks' feed intake, egg laying performance and egg quality. This paper shows that the constructed wetland removed as much as 64.44% of chemical oxygen demand (COD), 21.78% of total nitrogen (TN) and 23.02% of total phosphorus (TP). Both dissolved oxygen (DO) and the transparency of the wastewater were remarkably improved, with its transparency 2.5 times higher than that of the untreated wastewater. After the ducks were fed with water hyacinth, the average daily feed intake and the egg-laying ratio in the test group were 5.86% and 9.79% higher, respectively, than in the control group; the differences were both significant at the 0.01 probability level. The egg weight in the test group was 2.36% higher than in the control group (P < 0.05), but the feed conversion ratios were almost the same. The eggshell thickness and strength were among the egg qualities significantly increased in ducks fed with water hyacinth. We concluded that a water hyacinth system was effective for purifying wastewater from an intensive duck farm during the water hyacinth growing season, as harvested water hyacinth had an excellent performance as duck feed. We also discussed the limitations of the experiment.

Phytoremediation and metal uptake in food plants

This paper reviews some of our resent findings on metal uptake in phytotechnology and foodplants. The Cd concentration in wheat grains can be decreased by pytoextraction by Salixprior to wheat cultivation. Water spinach commonly grown in nutrient rich waste water areable to form methyl-Hg in new leaves, but high nutrient level in cultivation medium decreasesthe metal concentration in the plant. Wetland plants grown on mine tailings are able todecrease the formation of acid mine drainage from the tailings. Submerged plants can increasethe retention of metals in wetlands treating metal polluted water, but the efficiency dependson the quality of the inlet water. Plants can be used to prevent leakage of metals and nutrientsfrom dry covers containing sewage sludge on mine tailing impoundments. If the sealing layerbelow the cover layer consists of fly ash root penetration can be prevented while if it containsa mixture of sewage sludge and fly ash roots will grow into the sealing layer. Macro algae asfertilizers in agriculture increase the biomass production but also transfer Cd to the crop.Therefore, algae should be used in production of non food crops, however, not suitable forhemp cultivation.

Struvite Crystallization in Fed-Batch Pilot Scale and Description of Solution Chemistry of Struvite

struvite (MgNH 4PO 4·6H 2O) encrusts naturally in high turbulence zones of nutrient rich wastewater. Struvite has a potential to be used as slow release boutique fertilizer. This study aims to evaluate struvite precipitation potential using thermodynamic modelling. The thermodynamic model was developed using gPROMS process simulation software, incorporating the solution chemistry of magnesium, ammonium and phosphate. The simulation results describe the detailed speciation of solution used in fed-batch struvite crystallization. The solution speciation of struvite incorporates the concentration of free ions and the relevant complexes together with the solubility status of solution. Finally, this paper includes the investigation of struvite drying temperature using moisture analysing technique, together with the elemental analysis using powder XRD technique and the identification of struvite morphology using electron micrograph.

The prospects for willow plantations for wastewater treatment in Sweden

The concept of willow vegetation filters for the treatment of nutrient-rich wastewater has the potential to address two of our most serious environmental problems today -water pollution and climate change- in a cost-efficient way. Despite several benefits, including high treatment efficiency, increased biomass yields, improved energy and resource efficiency, and cost savings, willow vegetation filters have so far only been implemented to a limited degree in Sweden. This is due to various kinds of barriers, which may be the result of current institutional, structural and technical/geographical conditions. This paper discusses the prospects of a more widespread utilisation of willow plantations for wastewater treatment in Sweden, including existing incentives and barriers, based on current knowledge and experience. © 2005 Elsevier Ltd. All rights reserved.

Closing the nutrient loop between urban and rural area – wastewater and sludge utilization in Ner River Valley

For decades an area of 4 500ha of Ner River valley was used as a part of Łódź municipality wastewater treatment system. Sandy alluvial soils were irrigated with nutrient rich river water for high hay crop production.Nowadays wastewater treatment plant in Łódź discharges 2m3s−1 of wastewater and produces daily 30–35t of dry matter of sludge which can be utilized in the valley for energy biomass production.Of a great importance for sustainable development is the recirculation of nutrients between urban and rural areas. Reuse nutrient rich wastewater and sludge results in saving natural resources (mining rocks, forest wood) and protection of receiving water bodies.

Upgrading of the STP Uithoorn: treatment of nutrient rich wastewater from horticulture

The STP Uithoorn will be upgraded to accommodate the treatment of wastewater from a growing population and to meet more stringent nutrient discharge limits in 2006. In 2003 a system choice and preliminary design was made for the upgrading. A special feature is the nutrient rich wastewater flow from the rapidly developing horticulture in the area. Since the future loads from horticulture are highly uncertain, flexibility of the STP after upgrading is an important issue. A three stage system was selected: improved physical-chemical primary treatment, secondary treatment by activated sludge, and tertiary treatment by denitrifying filters. In this way an important part of the existing infrastructure can be reused, and flexibility is assured by constructing the tertiary treatment in modules and by providing a wide range of operational control possibilities. In this paper the process of system choice and selection of type of tertiary treatment are described, as well as the optimisation of the existing treatment. In order to determine the feasibility of allowing a high loading rate on the existing secondary clarifiers, a two-dimensional hydraulic model of the clarification process was used.

A small scale hydroponics wastewater treatment system under Swedish conditions

A treatment plant using conventional biological treatment combined with hydroponics and microalgae is constructed in a greenhouse in the area of Stockholm, Sweden. The treatment plant is built for research purposes and presently treats 0.559 m3 of domestic wastewater from the surrounding area per day. The system uses anoxic pre-denitrification followed by aerobic tanks for nitrification and plant growth. A microalgal step further reduces phosphorus, and a final sand filter polishes the water. During a three week period in July 2002 the treatment capacity of this system was evaluated with respect to removal of organic matter, phosphorus and nitrogen. 90% COD removal was obtained early in the system. Nitrification and denitrification was well established with total nitrogen reduction of 72%. Phosphorus was removed by 47% in the process. However, higher phosphorus removal values are expected as the microalgal step will be further developed. The results show that acceptable treatment can be achieved using this kind of system. Further optimisation of the system will lead to clean water as well as valuable plants to be harvested from the nutrient rich wastewater.

The use of wetlands in the Mississippi Delta for wastewater assimilation: a review

The use of wetlands for treatment of wastewaters has a number of important ecological and economic benefits. Adding nutrient rich treated wastewater effluent to selected coastal wetlands results in the following benefits: (1) improved effluent water quality; (2) increased accretion rates to help offset subsidence; (3) increased productivity of vegetation; and (4) financial and energy savings of capital not invested in conventional tertiary treatment systems. We present as case studies results from several wetlands that are receiving secondarily treated wastewater in coastal Louisiana. At one site where sedimentation accumulation was measured, rates of accretion increased significantly after wastewater application began in the treatment site (from 7.8 to 11.4 mm yr −1) and approached the estimated rate of regional relative sea level rise (RSLR) (12.0 mm yr −1). No corresponding increase was observed in an adjacent control site. This suggests that the application of nutrient-rich wastewater can help coastal wetlands survive sea level rise. In the same site, surface water nutrient reduction, from the effluent inflow to outflow (1600 m), ranged from 100% for nitrate-nitrogen (NO 3-N) to 66% for total phosphorus (P). At a second site, a forested wetland that has been receiving wastewater effluent for 50 years, N and P were both reduced by more than 90%. Nutrient reduction is due to three main pathways: burial, denitrification and plant uptake. Dendrochronological analysis at the second site revealed that stem growth increased significantly in the treatment site after wastewater applications began, and was significantly greater than an adjacent control site. Similar increases in productivity have been measured in a number of wetland treatment sites. Economic analyses comparing conventional and wetland systems indicate savings range from $500,000 to $2.6 million. In addition there are substantial energy savings.

Nutrient retention and nutrient-use efficiency in Phragmites australis stands after wasterwater application

The capacity of Phragmites australis to extract nutrients from its environment and to store them in plant tissue was studied in an infiltration wetland used for wastewater treatment. The aims of the study were to estimate the contribution of plant uptake to the overall nutrient removal efficiency of the wastewater treatment system and to determine measures to enhance the nutrient removal efficiency. The functional response of Phragmites australis to nutrient addition was studied at two levels of nutrient availability by comparing a wetland used for wastewater treatment with a natural, undisturbed wetland. In the nutrient-rich wastewater wetland, biomass production, nutrient content of plant tissue, shoot/root ratios, and translocation rates were much greater than in the natural wetland. In contrast, plant nutrient-use efficiencies of both nitrogen and phosphorus were much lower in the wastewater wetland. The lower nutrient-use efficiencies were probably due to (1) lower nutrient productivity, which was probably due to self-shading resulting in a lower photosynthetic activity, and (2) lower mean nutrient residence time, which can be explained by a higher litter production (higher shoot and leaf turnover). In the wastewater wetland, harvesting during winter removed only 9% of the total nitrogen input and 6% of the total phosphorus input associated with the loading of wastewater. The low nutrient removal efficiency by aboveground plant harvesting is caused by translocation of nutrients from shoots and leaves to rhizomes and roots in autumn. Nutrient removal efficiency of the wastewater wetland could be enhanced by 40–50% by harvesting at peak nutrient storage levels in the aboveground plant parts in August or September.

Impact of wastewater discharge on the channel morphology of ephemeral streams

AbstractThe impact of wastewater flow on the channel bed morphology was evaluated in four ephemeral streams in Israel and the Palestinian Territories: Nahal Og, Nahal Kidron, Nahal Qeult and Nahal Hebron. Channel changes before, during and after the halting of wastewater flow were monitored. The wastewater flow causes a shift from a dry ephemeral channel with intermittent floods to a continuous flow pattern similar to that of humid areas. Within a few months, nutrient‐rich wastewater flow leads to rapid development of vegetation along channel and bars. The colonization of part of the active channel by vegetation increases flow resistance as well as bank and bed stability, and limits sediment availability from bars and other sediment stores along the channels. In some cases the established vegetation covers the entire channel width and halts the transport of bed material along the channel. During low and medium size flood events, bars remain stable and the vegetation intact. Extreme events destroy the vegetation and activate the bars. The wastewater flow results in the development of new small bars, which are usually destroyed by flood flows. Due to the vegetation establishment, the active channel width decreases by up to 700 per cent. The deposition of fine sediment and organic material changed the sediment texture within the stable bar surface and the whole bed surface texture in Nahal Hebron. The recovery of Nahal Og after the halting of the wastewater flow was relatively fast; within two flood seasons the channel almost returned to pre‐wastewater characteristics. The results of the study could be used to indicate what would happen if wastewater flows were introduced along natural desert streams. Also, the results could be used to predict the consequences of vegetation removal as a result of human intervention within the active channel of humid streams. Copyright © 2001 John Wiley &amp; Sons, Ltd.