Land Application Of Wastewater Research Articles

Investigating the Mechanisms Impacting Soil Ca, Mg, and Na in Wastewater Land Application Systems Using Machine Learning Models

ABSTRACTWastewater land application is a widely accepted solution for addressing global water crisis, particularly in arid and semiarid regions, but it may cause soil Ca, Mg, and Na accumulation and result in soil degradation. The objective of this study was to investigate the underlying mechanisms impacting soil Ca, Mg, and Na in wastewater land application systems using tree‐based machine learning models. Using data collected from previous field studies, decision tree (DT), random forest (RF), and extreme gradient boosting decision trees (XGBoost) models were developed to predict soil Ca, Mg, and Na in wastewater land application systems. XGBoost models showed the best performance, with R2 and RMSE values of 0.999 and 18.9 mg/kg, 0.999 and 3.2 mg/kg, and 0.912 and 104 mg/kg on the training data and 0.989 and 345 mg/kg, 0.925 and 56.1 mg/kg, and 0.908 and 112 mg/kg on the test data for soil Ca, Mg, and Na prediction, respectively. Permutation importance analysis reveals that initial soil Ca and electrical conductivity (EC) and total irrigation amount, initial soil Mg, total precipitation and initial soil EC, and initial soil Na, total irrigation amount and wastewater Na were the top three predictive variables for soil Ca, Mg, and Na, respectively. Partial dependence analysis demonstrates how soil Ca, Mg, and Na changed with the predictive variables, and indicates that wastewater irrigation caused soil Ca, Mg, and Na accumulation. This study highlights the need for sustainable wastewater land application management to control soil sodium adsorption ratio and mitigate the risks of land degradation.

Emerging organic contaminants in the soil-plant-receptor continuum: transport, fate, health risks, and removal mechanisms.

There is a lack of comprehensive reviews tracking emerging organic contaminants (EOCs) within the soil-plant continuum using the source-pathway-receptor-impact-mitigation (SPRIM) framework. Therefore, this review examines existing literature to gain insights into the occurrence, behaviour, fate, health hazards, and strategies for mitigating EOCs within the soil-plant system. EOCs identified in the soil-plant system encompass endocrine-disrupting chemicals, surfactants, pharmaceuticals, personal care products, plasticizers, gasoline additives, flame retardants, and per- and poly-fluoroalkyl substances (PFAS). Sources of EOCs in the soil-plant system include the land application of biosolids, wastewater, and solid wastes rich in EOCs. However, less-studied sources encompass plastics and atmospheric deposition. EOCs are transported from their sources to the soil-plant system and other receptors through human activities, wind-driven processes, and hydrological pathways. The behaviour, persistence, and fate of EOCs within the soil-plant system are discussed, including sorption, degradation, phase partitioning, (bio)transformation, biouptake, translocation, and bioaccumulation in plants. Factors governing the behaviour, persistence, and fate of EOCs in the soil-plant system include pH, redox potential, texture, temperature, and soil organic matter content. The review also discusses the environmental receptors of EOCs, including their exchange with other environmental compartments (aquatic and atmospheric), and interactions with soil organisms. The ecological health risks, human exposure via inhalation of particulate matter and consumption of contaminated food, and hazards associated with various EOCs in the soil-plant system are discussed. Various mitigation measures including removal technologies of EOCs in the soil are discussed. Finally, future research directions are presented.

Comparative life cycle assessment of anaerobic digestion, lagoon evaporation, and direct land application of olive mill wastewater

Olive mill wastewater is a prominent waste stream in the Mediterranean countries, with its uncontrolled disposal in water recipients causing significant environmental issues. Anaerobic digestion has been extensively studied for the treatment of various agricultural waste streams. The scope of the present study was the environmental evaluation of the anaerobic digestion of three-phase olive mill wastewater for energy production in an anaerobic bioreactor. Regarding the environmental assessment of the process, the results indicate a lead in the proposed process compared with the baseline scenarios. Moreover, several environmental issues in terrestrial acidification and water eutrophication midpoint categories were exhibited by the digestate utilization. The implementation of the anaerobic digestion method averts an overall environmental damage of 5 mPt per 1000 kg of waste treated. For this reason, the implementation of the proposed method could be a sustainable alternative for wastewater treatment in olive oil production regions, aiming to circular economy.

Identifying sources of antibiotic resistance genes in the environment using the microbial Find, Inform, and Test framework.

Antimicrobial resistance (AMR) is an increasing public health concern for humans, animals, and the environment. However, the contributions of spatially distributed sources of AMR in the environment are not well defined. To identify the sources of environmental AMR, the novel microbial Find, Inform, and Test (FIT) model was applied to a panel of five antibiotic resistance-associated genes (ARGs), namely, erm(B), tet(W), qnrA, sul1, and intI1, quantified from riverbed sediment and surface water from a mixed-use region. A one standard deviation increase in the modeled contributions of elevated AMR from bovine sources or land-applied waste sources [land application of biosolids, sludge, and industrial wastewater (i.e., food processing) and domestic (i.e., municipal and septage)] was associated with 34-80% and 33-77% increases in the relative abundances of the ARGs in riverbed sediment and surface water, respectively. Sources influenced environmental AMR at overland distances of up to 13 km. Our study corroborates previous evidence of offsite migration of microbial pollution from bovine sources and newly suggests offsite migration from land-applied waste. With FIT, we estimated the distance-based influence range overland and downstream around sources to model the impact these sources may have on AMR at unsampled sites. This modeling supports targeted monitoring of AMR from sources for future exposure and risk mitigation efforts.

Nutrient recovery in cultured meat systems: Impacts on cost and sustainability metrics.

A growing global meat demand requires a decrease in the environmental impacts of meat production. Cultured meat (CM) can potentially address multiple challenges facing animal agriculture, including those related to animal welfare and environmental impacts, but existing cost analyses suggest it is hard for CM to match the relatively low costs of conventionally produced meat. This study analyzes literature reports to contextualize CM's protein and calorie use efficiencies, comparing CM to animal meat products' feed conversion ratios, areal productivities, and nitrogen management. Our analyses show that CM has greater protein and energy areal productivities than conventional meat products, and that waste nitrogen from spent media is critical to CM surpassing the nitrogen use efficiency of meat produced in swine and broiler land-applied manure systems. The CM nutrient management costs, arising from wastewater treatment and land application, are estimated to be more expensive than in conventional meat production. Overall, this study demonstrates that nitrogen management will be a key aspect of sustainability in CM production, as it is in conventional meat systems.

Extraction, analysis, and occurrence of per- and polyfluoroalkyl substances (PFAS) in wastewater and after municipal biosolids land application to determine agricultural loading

Given the ubiquitous detection of per- and polyfluoroalkyl substances (PFAS) within numerous soil and water environmental compartments, there is a need for global understanding of current methodologies for extracting water, solids, polar organic chemical integrative samplers (POCIS), and plant tissue for these substances. This study provides details of several current extraction methods, demonstrates the use of POCIS in monitoring these compounds in a wastewater environment, and provides evidence of detectable levels of certain PFAS compounds within Midwestern municipalities and agroecosystems. Validated extraction procedures help characterize occurrence and release of 18 PFAS in a midwestern wastewater treatment plant (WWTP), surface water, runoff after land application of biosolids to agricultural test plots, infiltration into topsoil, and uptake by grain sorghum. Of the compounds measured, 14 PFAS were detected at least at one sampling site or type. The average total (Σ PFAS) dissolved phase time-weighted average (TWA) concentration in wastewater influent, effluent and in the upstream and downstream effluent mixing zone (EMZ) sites in the receiving stream, respectively, were 27.9, 132, 37.7, and 71.4 ng L−1. Long-chain PFAS dominated most of the aqueous compartments, and perfluoroalkyl acids (PFAAs) occurred in the WWTP and receiving surface waters. Total Σ14 PFAS measured in municipal biosolids applied to soils were 22.9 ng g−1 dw with long-chain PFAS comprising 77.5% of the cumulative PFAS mass. Perfluorooctanesulfonic acid (PFOS) was the most abundant compound detected in biosolids at the highest concentration (9.40 ng g−1 dw). Accumulation in WWTP biosolids was estimated to occur at a rate of 72.8 g day−1 dw based on the difference between influent and effluent time weighted average concentrations. PFAS were detected in both surface soil and runoff after land application of biosolids, but also in control plots consistent with background PFAS contamination. PFAS concentrations in surface runoff decreased over time from plots treated with biosolids. These results provide evidence of the introduction of PFAS to agroecosystems from wastewater effluent and land application of biosolids in the Midwest.

State Regulations and Guidelines for Wastewater Reuse for Irrigation in the U.S.

The objective of this paper is to present an overview of state regulations and guidelines for wastewater reuse for irrigation. Land application of wastewater in the U.S. began in the 19th century when it was considered the safest and best method for wastewater disposal. According to the Environmental Protection Agency (EPA), 27 states have regulations for wastewater reuse and 11 states have guidelines for reuse. Some states have no regulations or guidelines for wastewater reuse. For urban wastewater reuse for irrigation where public access is not restricted and for irrigation of food crops, many of the states require additional levels of treatment beyond secondary treatment, which may include oxidation, coagulation, and filtration and high levels of disinfection. California, Arizona, Texas, and Florida were the earliest states to establish water reuse programs and account for the majority of wastewater reuse for irrigation in the U.S. Several of the challenges to increase wastewater reuse are water rights in the western states and a lack of funding for new projects.

Building resilience into water management through public engagement

Water resources of the United States (US), most of which are associated with river basins and managed by water utilities, are influenced by multiple landowners and land uses across diverse political jurisdictions with varying stakeholder interests. Water utilities occupy a challenging domain where they are tasked with simultaneously providing affordable and safe water while maintaining environmental quality. When periodic crises occur, the water users are often poorly prepared to understand the tradeoffs and consequences of water management decisions. The increasing prevalence of water insecurity in the US and globally creates both opportunity and necessity to use public engagement with science (PES) to enhance the sustainability of water resources. We consider PES to include a range of knowledge necessary to develop a resilient and sustainable water management strategy based on ecological, environmental, and engineering principles. We suggest that global water insecurity creates a PES opportunity for the Society for Freshwater Science and similar technical and scientific organizations. We provide examples and explore PES actions that serve as a guide for engagement. Fundamental to PES in natural resources management is creating a culture of mutual learning among groups with different interests and responsibilities, in this case researchers, water managers, conservation organizations, and the public as water users. We also provide a case study of successful PES based on our experience with the Upper Flint River Working Group (UFRWG) in Georgia, USA. The UFRWG has been working to promote water sustainability for 7 y and illuminates a critically important aspect of PES: that engagement must be responsive to the diverse experiences of stakeholders (in resources, expertise, capacity, timelines, lexicon, political economy, and so on) and be planned over appropriate timeframes to ensure success in the realm of process as well as results. The UFRWG can point to improved communication between utilities, early recognition of potential water scarcity, aggressive conservation measures, changing attitudes towards land application of wastewater vs return flows of treated water, and consideration of urban green infrastructure to manage stormwater runoff as evidence of success. Changes in water management that have been made by the UFRWG are a testament that PES strategies can be powerful tools in the natural resources management arena.

Controlled Land Application of Olive Mill Wastewater (OMW): Enhance Soil Indices and Barley Growth Performance in Arid Environments

Olive oil industry generates a considerable amount of olive mill wastewater (OMW) each year, which increases the difficulties for successful processing and disposing. A possible and potential alternative is controlled application of OMW into the land. In these two fields’ experiments, we investigated a sustainable controlled land application of OMW to enhance soil properties and improve barley production under rainfed conditions. OMW was spread at five application rates (20, 40, 60, 80, and 120 m3 ha−1) in addition to the control at two sites, Rabba and Ghweer. The physicochemical characterizations of OMW were determined throughout the season. Physicochemical properties of soil were measured after 2 weeks of OMW spreading after planting and after barley harvest. Leaf nutrient content as well as other growth performance has been measured. The results of this study showed no harmful effect of OMW application for all application rates on growth parameters of barley as well as soil properties at both locations. Under all application rates, OMW has increased soil organic matter and nutrient contents, which could reduce the use of chemical fertilizer. There was a significant increase in barley growth in OMW treatments for dry weight (DM) (14 and 22%), biological yield (BYLD) (49 and 34%), grain yield (GYLD) (41 and 47%), and straw yield (SYLD) (55 and 31%) at Rabba and Ghweer sites, respectively. The results exhibited the benefit of controlled application of OMW. However, long-term effect of OMW application needs more study, and local legislative is necessary.

Urban pollution control strategy: SBR technology to treat agricultural waste from pig farm in Indonesia

Reduction of food rations and shortages is one of the impacts of the increasing human population. Food sector industries then try to cope with the fast growing number of customers. Agribusiness sector gains its popularity in these recent years, including pig farm. The increase trend of animal farming industry is likely to bring increasing pollution problem unless effective treatment methods are used. The main problems related to the pig farm include odor nuisance and pig manure disposal. The existing land application of piggery wastewater is the traditional way to discharge the wastewater. This may yield in land and water contamination, due to the accumulation of unused nutrients by crop plant. A case study of a large commercial pig farm from Australia is proposed to apply in smaller scale in Indonesia. Operational strategies for the small-scale SBR (Sequencing Batch Reactor) treating piggery effluent were developed based on lab-scale experiments. Due to SBR characteristics, which are money-saving and space-saving, it is very suitable to be applied in urban area. An economic evaluation was made of various process options. The cost estimation showed that SBR is a cost effective process, allowing operational batches to be adjusted to reduce unnecessary aeration cost. A reduction in the aeration cost was achieved by shortening the batch time from 24-h to 8-h. A comparison of three different SBR options showed that smaller size reactors could be more flexible and cost effective when compared with the larger ones.

The in situ treatment of synthetic musk fragrances in groundwater

AbstractSynthetic musk fragrances (SMFs) have been shown to be micropollutants in various aquatic and groundwater systems, often occurring at microgram per liter concentrations. Studies have shown that the most commonly detected SMFs in water are nitro musks and polycyclic musks. The SMFs are typically introduced into the environment in continuous streams such as from wastewater and land application of wastewater or sludge generated during wastewater treatment. Various studies for the treatment of SMFs have been undertaken for wastewater but studies for the treatment of SMFs in groundwater are limited, especially for in situ treatment. A pilot‐scale test was conducted to determine if the use of colloidal activated carbon (CAC) could effectively reduce dissolved concentrations of nitro and polycyclic synthetic musk compounds including musk xylene, musk ketone, galaxolide, and tonalide. The pilot test was carried out downgradient of a septic system in Central Canada where a series of nitrification and denitrification reactions are occurring in an unconfined aquifer. A 10‐weight percent CAC solution was injected into a series of temporary direct push injection points to target the synthetic musk plume. The plume contained galaxolide and tonalide concentrations up to 687 and 187 nanograms per liter (ng/L), respectively, while the concentrations of musk ketone and musk xylene were below the method detection limit (20 ng/L). A total of 13,950 liters of CAC solution was injected during one injection event. The pilot test results indicated that the CAC was effectively delivered to the target injection zone resulting in an increase in total organic carbon concentrations within the saturated soil greater than two orders of magnitude compared to the background concentrations. Analyses of the groundwater chemistry before and post‐injection indicated that the CAC had no detrimental impact on the groundwater quality while reducing the concentration of dissolved galaxolide and tonalide within the plume to below the method detection limits within 51 days of injection with the exception of two of the 14 wells monitored which had galaxolide and tonalide concentrations up to 78 and 35 ng/L. Within 6 months of application, the concentrations of galaxolide and tonalide had decreased to below the method detection limits. Subsequent monitoring of the groundwater quality over a one‐year period failed to detect galaxolide and tonalide, suggesting that the CAC was effective in attenuating the galaxolide and tonalide.

Response of Soil Chemical Properties to Irrigation with Winery Wastewater on a Well-drained Sandy Soil

Most wineries in South Africa dispose of their wastewater through land application. This is carried out by irrigating small areas of cultivated pasture with the wastewater or ponding, with the former being the more general practice. Land application of winery wastewater results in the accumulation of potassium (K+) and sodium (Na+) in the soil and leaching of calcium (Ca2+) and magnesium (Mg2+).This could lead to long term instability of soil structure. The objective of this study was to investigate the effect of irrigation with winery wastewater on chemical soil properties and potential environmental impacts. Therefore, an existing grazing paddock at a winery near Rawsonville was selected where wastewater had been applied for many years. Due to the high volumes of wastewater irrigation plus rainfall, the inevitable over-irrigation leached large amounts of cations, particular K+ and Na+, beyond 90 cm soil depth at the selected study site. These leached elements are likely to end up in natural water resources in the long run. Irrigation with winery wastewater did not have a pronounced effect on soil pH(KCl). This was probably due to the decomposition of organic matter, and the fact that the applied salts were leached beyond 90 cm depth. The study confirmed that disposal of winery wastewater through land application can only be recommended where wastewater application will not exceed the water requirement of the crop as well as the water holding capacity of the soil which is being irrigated.

Computational modeling of wastewater land application treatment systems to determine strategies to improve carbon and nitrogen removal

Land application of domestic and food processing wastewater is used due to its low cost, energy use, and maintenance. Design procedures are generally based on empirical relationships that may not account for critical site and waste-specific conditions. A mathematical model was utilized to simulate the complexity of wastewater land application. Multiple scenarios were run to determine system performance as measured by chemical oxygen demand (COD) and the nitrification/denitrification process. The modeling results showed that COD and nitrification occurred within the first 15.4 cm of a sandy loam soil. Increasing the dosing frequency slightly reduced the COD effluent concentration. Complete denitrification does not occur in a typical land application wastewater treatment system. In a domestic wastewater land application system, up to 32% of nitrate can be removed by increasing the dosing frequency and providing more organic carbon. In a food processing wastewater land application system, up to 56% of nitrate can be removed by increasing the dosing frequency and hydraulic and organic loadings. HYDRUS CW2D modeling is a valuable design tool to simulate multiple operation strategies and predict carbon degradation, nitrification, and denitrification. The model result can provide operational strategies to maximize the treatment while minimizing environmental impacts.

Annual Dynamics of Winery Wastewater Volumes and Quality and the Impact of Disposal on Poorly Drained Duplex Soils

The composition and volume of winery wastewater change throughout the year. Quality is usually at its worst when vintage operations are dominated by the production of red wines. The objective of this study was to investigate the annual dynamics of winery wastewater volumes and quality, as well as the effect of winery wastewater irrigation on the chemical soil properties of a poorly drained duplex soil. The study was conducted over two and half years. The wastewater contained a high concentration of potassium (K+) and low levels of sodium (Na+). The results of the study confirmed that winery wastewater did not comply with South African national legislation for wastewater irrigation with regard to chemical oxygen demand (COD) and pH throughout the study period, while some prominent spikes were observed in sodium adsorption ratio (SAR) and electrical conductivity (EC). Land application of winery wastewater resulted in the accumulation of high levels of K+ in the soil. It is important to note that this study represents the worst-case scenario, i.e. large amounts of wastewater were disposed of on a small surface, particularly during harvest and in winter. Due to the high volumes of wastewater irrigation plus rainfall, the inevitable over-irrigation leached large amounts of K+ beyond 90 cm soil depth. Unfortunately, the leached elements are bound to end up in natural water resources, resulting in the pollution of the environment.

Water Reuse: From Ancient to Modern Times and the Future

Domestic wastewater (sewage) has been used for irrigation and aquaculture since the Bronze Age (ca. 3,200-1,100 BC) by prehistoric civilizations (e.g. Chinese, Egyptian, Indus Valley, Mesopotamian, and Minoan). In historic times (ca. 1,000 BC-330 AD), wastewater was disposed of or used for irrigation and fertilization purposes by the Greek civilization and later by the Romans in areas surrounding cities (e.g. Athens and Rome). In more recent history, the practice of land application of wastewater for disposal and agricultural use was utilized first in European cities and later in USA. Today, the planning and implementation of water reclamation and reuse projects is occurring throughout the world. Recycled water is now used for almost any purpose including potable use. This paper provides a brief overview of the evolution of water reuse over the last ca. 5,000 years. Understanding the practices and solutions of the past, provides a lens with which to view present and future challenges in a highly-urbanized world.

Modeling fecal bacteria transport and retention in agricultural and urban soils under saturated and unsaturated flow conditions

Pathogenic bacteria, that enter surface water bodies and groundwater systems through unmanaged wastewater land application, pose a great risk to human health. In this study, six soil column experiments were conducted to simulate the vulnerability of agricultural and urban field soils for fecal bacteria transport and retention under saturated and unsaturated flow conditions. HYDRUS-1D kinetic attachment and kinetic attachment-detachment models were used to simulate the breakthrough curves of the experimental data by fitting model parameters. Results indicated significant differences in the retention and drainage of bacteria between saturated and unsaturated flow condition in the two studied soils. Flow under unsaturated condition retained more bacteria than the saturated flow case. The high bacteria retention in the urban soil compared to agricultural soil is ascribed not only to the dynamic attachment and sorption mechanisms but also to the greater surface area of fine particles and low flow rate. All models simulated experimental data satisfactorily under saturated flow conditions; however, under variably saturated flow, the peak concentrations were overestimated by the attachment-detachment model and underestimated by the attachment model with blocking. The good match between observed data and simulated concentrations by the attachment model which was supported by the Akaike information criterion (AIC) for model selection indicates that the first-order attachment coefficient was sufficient to represent the quantitative and temporal distribution of bacteria in the soil column. On the other hand, the total mass balance of the drained and retained bacteria in all transport experiments was in the range of values commonly found in the literature. Regardless of flow conditions and soil texture, most of the bacteria were retained in the top 12 cm of the soil column. The approaches and the models used in this study have proven to be a good tool for simulating fecal bacteria transport under a variety of initial and boundary flow conditions, hence providing a better understanding of the transport mechanism of bacteria as well as soil removal efficiency.

Nitrogen, phosphorus, calcium, and magnesium applied individually or as a slow release or controlled release fertilizer increase growth and yield and affect macronutrient and micronutrient concentration and content of field-grown tomato plants

The U.S. Environmental Protection Agency (USEPA) has restricted concentrated animal feeding operation (CAFO) release of waste products into U.S. waters. These waste products must be disposed of using best management practices. Most of the waste is spread on cropland, but some operations have found other creative uses for waste products. Use of a phosphorus (P) reduction system to remove P from wastewater results in magnesium ammonium phosphate (MAP), a slowly soluble fertilizer. Using a P reduction system will not eliminate the need for land application of manure and wastewater, but it reduces the nutrient load in the waste that is applied thereby making compliance with regulations easier. In the first year of this study, MAP was compared to a controlled release fertilizer (CRF) with a similar nutrient element ratio on plant growth, fruit yield, nitrogen (N), P, potassium (K), calcium (Ca), magnesium (Mg), iron (Fe), manganese (Mn), and zinc (Zn) concentration in tomato (Solanum lycopersicum L. ‘Mountain Fresh Plus’) plant parts. Plant growth and fruit production were similar with the two fertilizers, but the number of tomato culls was greater with either fertilizer than on control plants. Foliar N, P, Ca, and Mg concentration did not differ regardless of fertilizer treatment. Plants fertilized with CRF had a greater leaf K concentration than those fertilized with MAP, but foliar K concentration did not differ between fertilized and nonfertilized plants. Iron and Mn concentration in above-ground vegetative plant parts (stems and leaves) did not differ regardless of fertilizer treatment, but Zn concentration increased linearly as CRF increased. In the second year, MAP, each of the essential elements contained in MAP separately, and a hand mixture of each of these elements was tested for their effect on tomato plant growth, fruit yield, and tissue N, P, K, Ca, Mg, Fe, Mn, and Zn concentration and content. Magnesium ammonium phosphate and the hand mixture of fertilizer resulted in greater above-ground biomass excluding fruit stem weight and fruit yield than any of the individual nutrient treatments. Calcium sulfate resulted in a greater number and weight of tomatoes harvested than MAP. Nitrogen concentration did not differ among the fertilizer treatments for roots, stems, or leaves, but N content was greater in red fruit with the hand mix of fertilizer than with no fertilizer or with ammonium sulfate or Mg oxide. In immature green fruit at termination of the study, N content was greater with no fertilizer or Ca sulfate than with MAP or triple superphosphate (TSP). Phosphorus, K, and Ca concentrations did not differ among fertilizer treatments for any tissue tested. Magnesium concentration in green tomatoes differed among fertilizer treatments such that Mg concentration of green tomatoes from plants fertilized with TSP was greater than Mg concentration of green tomatoes fertilized with ammonium sulfate or Mg oxide. Phosphorus and K content of green fruit differed among fertilizer treatments with P and K concentration highest in green fruit from plants fertilized with Ca sulfate and lowest in green fruit from plants fertilized with MAP or TSP. Iron and Mn concentrations did not differ among fertilizer treatments for any tissue tested. Zinc concentration in leaves was greater when plants were fertilized with MAP, TSP, Ca sulfate, or Mg oxide than with ammonium sulfate. Zinc concentration of green fruit was greater when fertilized with MAP than with the hand mix, Ca sulfate or Mg oxide. Iron content was highest in green fruit from plants fertilized with TSP and lowest in plants fertilized with ammonium sulfate or control plants. Manganese content of leaves from control plants was greater than that of plants receiving ammonium sulfate while red fruit from plants fertilized with the hand mix had a greater Mn content than red fruit from any other treatment. Foliar Zn content was greater in plants fertilized with Ca sulfate than in those fertilized with the hand mix, ammonium sulfate, or TSP. In contrast, Zn content of red fruit fertilized with the hand mix was greater than for red fruit in any other treatment. Green fruit from control plants and those receiving MAP had a greater Zn content than plants fertilized with the hand mix, TSP, or Mg oxide. Fertilizer application increased Fe, Mn, and Zn content of several plant tissues. None of the labels of fertilizers applied stated that they contained micronutrients; however, small amounts of contamination were possible. Differing micronutrient contents of various plant tissues among fertilizer treatments were probably associated with other elements affecting plant growth or nutrient uptake. The nutrient elements present in the various fertilizers were not always the nutrient elements affected in the plants likely due to another element that may have limited plant growth or nutrient uptake.

Hydrologic Impacts of Municipal Wastewater Irrigation to a Temperate Forest Watershed.

Land application of municipal wastewater to managed forests is an important treatment and water reuse technology used globally, but the hydrological processes of these systems are not well characterized for temperate areas with annual rainfall of 1200 mm or greater. This study evaluated the impact of municipal wastewater irrigation to the local water balance at a 3000-ha land application facility where secondary-treated wastewater is land applied to a mixed hardwood-pine forest over 900 ha. Stable isotopes of hydrogen (H) and oxygen (O), chloride concentrations, and specific conductance were used in combination with hydrometric measurements to estimate the wastewater composition in groundwater, surface water, and at the watershed outlet during dry and wet seasonal periods and during one large rainfall event. Wastewater and water bodies receiving irrigation were found to have significantly higher δH, δO, specific conductance, and chloride concentrations. Using these tracers, a two-component, three-end member geochemical mixing model estimated mean wastewater compositions in the surficial aquifer receiving irrigation from 47 to 73%. Surface water onsite was found to reflect the high wastewater composition in groundwater. Land-applied wastewater contributed an estimated 24% of total streamflow, with the highest wastewater compositions in surface water observed during major storm events and at low-flow conditions. Groundwater and surface water within the watershed were found to have proportionally higher wastewater compositions than expected based on the proportion of irrigation to rainfall received by these areas.

Characterisation of winery wastewater from continuous flow settling basins and waste stabilisation ponds over the course of 1 year: implications for biological wastewater treatment and land application.

Wineries generate 0.2 to 4 L of wastewater per litre of wine produced. Many cellars make use of irrigation as a means of disposal, either directly or after storage. In order to consider the potential downstream impacts of storage/no storage, this study critically compared the seasonal organic and inorganic composition of fresh winery effluent with effluent that had been stored in waste stabilisation ponds. Ethanol and short chain volatile fatty acids were the main contributors to chemical oxygen demand (COD), with average concentrations of 2,086 and 882 mgCOD/L, respectively. Total phenolics were typically present in concentrations <100 mg/L. The concentration of sodium from cleaning agents was higher in the non-crush season, while the converse was true for organics. The effluent was nitrogen-deficient for biological treatment, with COD:N ratios of 0.09 to 1.2. There was an accumulation of propionic and butyric acid during storage. The composition of the pond effluent was more stable in character, and it is possible that bacterial and algal nitrogen fixation in such systems may enhance biological wastewater treatment by natural nitrogen supplementation. It is therefore recommended that if land requirements can be met, winery effluent should be stored in ponds prior to treatment.

Distribution of antibiotic resistance genes (ARGs) in anaerobic digestion and land application of swine wastewater

Swine farm and the adjacent farmland are hot spots of ARGs. However, few studies have investigated the on-site occurrence of ARGs distributed in the process of anaerobic digestion (AD) followed by land application of swine wastewater. Two typical swine farms, in southern and northern China respectively, with AD along with land application were explored on ARG distributions. ARGs were highly abundant in raw swine wastewater, AD effectively reduced the copy number of all detected ARGs (0.21–1.34 logs removal), but the relative abundance with different resistance mechanisms showed distinctive variation trends. The reduction efficiency of ARGs was improved by stable operational temperature and longer solid retention time (SRT) of AD. ARGs in soil characterized the contamination from the irrigation of the digested liquor. The total ARGs quantity in soil fell down by 1.66 logs in idle period of winter compared to application period of summer in the northern region, whereas the total amount was steady with whole-year application in south. Some persistent (sul1 and sul2) and elevated ARGs (tetG and ereA) in AD and land application need more attention.