Effluent Renovation Research Articles

Kinetic studies on phosphorus sorption by selected soil amendments for septic tank effluent renovation

A systematic kinetic study of phosphorus (P) sorption by various materials in the soil infiltration system of septic tanks was undertaken by following the time course of P sorption by sorbents in contact with various P solutions over periods up to 360 days. Uptake of P seemed to consist of two distinct stages. Initial uptake was very rapid and this phase was completed in 4 days or less. A slower removal stage followed for some materials over many months. Phosphorus sorption during the fast reaction stage appeared to be associated with the soluble Ca content of the materials. The fast reaction of calcareous materials accounted for the bulk (>70%) of the total P removed. Merribrook loamy sand exhibited the highest proportion of P sorption during the slow phase. It should be noted, however, that for solution P concentrations in the range found in typical effluents (approximately 20 mg L(-1)) the fast reaction phase seemed to be responsible for virtually all P removed. None of the six kinetic formulae examined possessed the sophistication and detail needed to portray accurately the time course of P sorption for all the sorbents investigated. The Elovich equation and the kinetic modification of the Freundlich isotherm expression appeared to provide a reasonable fit of the experimental data.

Assessment via discriminant analysis of soil suitability for effluent renovation using undisturbed soil columns

The use of onsite wastewater treatment systems for the treatment and dispersal of effluent is common in urban fringe areas which are not serviced by centralised wastewater collection systems. However, due to inappropriate siting and soil characteristics, the inherent failure of these systems, in particular subsurface soil treatment systems, are numerous. In order to ensure that these systems are capable of providing adequate treatment and dispersal of effluent in the long term, it is essential that the soils' ability to both renovate as well as dispose of discharged effluent is adequately assessed. This paper discusses the outcomes of a research study undertaken through the use of undisturbed soil columns to assess the ability of different soil types to treat and dispose of primary treated effluent. Discriminant analysis (DA) was utilised for classification of the various soil types based on their respective physical and chemical characteristics and to identify relative changes in each soil type after an extended period of application of effluent. Ferrosol and Dermosol soils were found to provide the most satisfactory conditions for effluent renovation. Kurosol, Sodosl and Chromosol soils even though were found to provide suitable means for removing effluent pollutants, reductions in the soils' permeability over time indicated that these soils may not be appropriate for long term effluent treatment. Finally, Podosol soils were found to have minimal ability to provide adequate treatment of effluent.

Framework for soil suitability evaluation for sewage effluent renovation

Current methods of establishing suitable locations for onsite wastewater treatment systems (OWTS) are inadequate, particularly in light of the numerous cases of onsite system failure and the resulting adverse consequences. The development of a soil suitability framework for assessing soil suitability for OWTS allows a more practical means of assessment. The use of multivariate statistical analysis techniques, including Principal Component Analysis (PCA) and multi-criteria decision aids of PROMETHEE and GAIA, enabled the identification of suitable soils for effluent renovation. The outcome of the multivariate analysis, together with soil permeability and drainage characteristics permitted the establishment of a framework for assessing soil suitability based on three main soil functions: (1) the ability of the soil to provide suitable effluent renovation, (2) the permeability of the soil, and (3) the soil’s drainage characteristics. The developed framework was subsequently applied to the research area, Gold Coast, Queensland, Australia, and the use of standard scoring functions were utilised to provide a scoring system to signify which soils were more suitable for effluent renovation processes. From the assessment, it was found that Chromosol and Kurosol soils provided the highest level of effluent renovation, closely followed by Ferrosol and Dermosol, Kandosol and Rudosol soil types. Tennosol and Podosol soil types were found to have a significantly lower suitability, with Hydrosol soils proving the least suitable for renovating effluent from OWTS.

Use of chemometrics methods and multicriteria decision-making for site selection for sustainable on-site sewage effluent disposal

This paper presents a study undertaken to evaluate site suitability for sewage effluent renovation based on physico-chemical characteristics of the soil. The results obtained showed that as the soil becomes acidic, the phosphorus concentration in the soil reduces accordingly. The chloride ion concentration was found to be a reliable indicator for evaluating the soil capacity to remove nitrogen. A high cation exchange capacity (CEC) can enhance the renovation of sewage effluent. Soils with high quartz content had a low CEC with high organic matter content (OM) being able to compensate. Therefore, an understanding of the micro-nutrients in the soil, organic matter content and chloride ion concentration are important. To facilitate a multi-variate approach for site selection, multicriteria decision-making (MCDM) methods, PROMETHEE and GAIA, were applied for analysis of a sequence of three matrices consisting of 8, 16, and 48 soil site objects, respectively, and seven soil property parameters. Matrix models and the interpretation of results are discussed in detail. From these analyses, PROMETHEE II net outranking flows, ϕ, found that two sites were always among the top three ranks of the three matrix models, which suggested that they were the most suitable for sewage effluent renovation. The criteria CEC and OM, were particularly important for the selection of these better sites, but pH and Cl − attributes discriminated the weaker performing sites from the better ones; as well the PO 4 3− and the NH 3–N criteria were in general opposition to CEC, OM, pH and Cl − but were much less effective as discriminators. Consideration of net outranking flows suggested an approach method for the selection of other possibly suitable sites for sewage effluent renovation.

An Investigation into the role of site and soil characteristics in onsite sewage treatment

The onsite treatment of sewage is common in all rural and regional areas of the world. Due to the public health and environmental risks that these treatment systems pose, the need for adopting performance-based management strategies is gaining increasing recognition. This demands the establishment of performance objectives for onsite sewage treatment and disposal which are based on stringent scientific analysis. A research project was undertaken to identify and investigate the role of influential site and soil characteristics in the treatment performance of subsurface effluent disposal areas. The treatment performances of a number of septic systems on a range of site and soil conditions were investigated together with detailed soil analysis. The changes to soil physico-chemical characteristics of the disposal area due to effluent application and its effluent renovation capacity were found to be directly related to the subsurface drainage characteristics. Significant changes to exchangeable cations and chemical parameters such as pH, electrical conductivity and cation exchange capacity (CEC) can result due to subsurface effluent application. A relationship exists between chemical parameters such as exchangeable Na and Ca:Mg ratio and CEC. A strong correlation also exists between the depth to the restrictive subsurface horizon and observed treatment performance. The study confirmed that soil chemistry can be a valuable predictive tool for evaluating the long-term performance of sewage effluent disposal systems particularly in poorly drained sites.

In vitro selection of duckweed geographical isolates for potential use in swine lagoon effluent renovation

Plant-based systems for nutrient sequestration into valuable biomass have the potential to help avoid the environmental problems associated with the disposal of large volumes of animal waste. The objective of this study was to select superior duckweed ( Lemnaceae) genotypes for the utilization of nutrients in animal wastes. A two-step protocol was used to select promising duckweed geographic isolates to be grown on swine lagoon effluent. Forty-one geographic isolates from the worldwide germplasm collection were used in an in vitro screening test, because they were noted to be fast-growing genotypes during routine collection maintenance. In vitro screening was accomplished by growing geographic isolates on a synthetic medium that approximated swine lagoon effluent in terms of nutrient profile, total ionic strength, pH, and buffering capacity. Large differences among geographic isolates were observed for wet weight gain during the 11-day growing period, percent dry weight, and percent protein in dry biomass. Total protein production per culture jar differed 28-fold between the most disparate of the 41 geographic isolates and was the variable used for selection of superior geographic isolates. The challenge of eight of the 41 geographic isolates with full-strength swine lagoon effluent in the greenhouse led to the selection of three that are promising as genotypes to be grown on lagoon effluent.

Nitrogen removal and conversion by duckweed grown on waste-water

Duckweed was grown in outdoor ponds for the purpose of domestic waste-water treatment, recycling of the nutrient and effluent renovation. Growth of the plant was examined at two pond depths and various hydraulic retention times. Temperature stratification in the ponds probably affected ammonia uptake. Dry yield of the duckweed approached 15 g m −2 day −1 with a protein content of about 30% in the short retention-time treatments. Effluent quality was at the secondary level and met criteria for re-use for agricultural irrigation.

Performance of the duckweed species Lemna gibba on municipal wastewater for effluent renovation and protein production

An outdoor experiment was conducted in miniponds to evaluate the performance of Lemna gibba, a duckweed species, as a domestic wastewater stripper. Duckweed is one of the floating plants with a high capability of ammonia uptake and assimilation rate into valuable protein. The results indicate that under adequate operational conditions, depending mainly on the organic loading, the effluent quality meets irrigation reuse criteria and protein yield of the duckweed may reach 12 ton/ha per year, far above other conventional field crops.

Waste Water Recycling by Duckweed for Protein Production and Effluent Renovation

Waste water treatment and recycling facilities are becoming increasingly necessary in arid zones, especially in the light of the shortage of conventional water sources. The simultaneous treatment of waste water and the production of duckweed in a pond system, as an alternative protein source, is an attractive proposition for solving the feed and water shortage problem. Outdoor experiments conducted in mini-ponds showed that duckweed ponds may be highly competitive with existing secondary treatment methods. The duckweed biomass, with a crude protein content of above 30% (dry weight), may be used as an alternative source for animal feed. The ease of the duckweed harvesting makes the system even more economically attractive. The work describes the basic outdoor biotechnology aimed at eliminating the superior organic loading in the pond as given by the ratio of COD and NH+4 in the raw domestic sewage. This ratio was examined in respect to the retention time of the wastes in the ponds and protein production by the floating vascular plant biomass.

Quality of Percolate Water After Treatment of a Municipal Wastewater Effluent by a Crop Irrigation System

AbstractCrop management effects on the renovation of municipal wastewater effluent were studied in a 6‐year field experiment. A randomized split‐plot block design was used, with corn (Zea mays L.) and forage grasses (reed canarygrass, Phalaris arundinacea L.) as crops and effluent application rates of none, ∼0.05, and ∼0.10 m week−1. Nitrogen, phosphorus, potassium, sodium, and chloride were measured in percolating soil water during 5 years under corn and 3 years under forage grasses to assess the quality of renovated wastewater. Nitrogen concentrations were generally below 10 mg L−1, with total applications ranging between 200 and 970 kg N ha−1 year−1. Nitrogen concentrations also were consistently lower under effluent treatments as compared with fertilized controls and lower under forage crops than under corn. Nitrogen levels increased significantly with increased application rates, especially under corn crops and only occasionally exceeded 10 mg L−1 during early and late season when applications surpassed crop uptake demands. Low P concentrations (< 0.05 mg L−1) in percolate water verified nearly complete removal by the soilcrop system except during the final 2 years under corn when concentrations increased about fivefold to 0.7 mg L−1. Potassium levels suggested a continuing removal from the effluent. Sodium and chloride concentrations began at low levels and increased during the first 1 to 2 years of irrigation until they approached the concentrations of the effluent. These results indicate that high N demand crops such as forage grasses have the potential for better renovation of effluent than corn at high application rates, but at lower rates corn will renovate effluent to acceptable N concentrations.

Renovation of Septic Tank Effluent in Sand‐Clay Mixtures

AbstractSand required by Pennsylvania code for use in elevated sand mounds is not specified by sand mineralogy but does require 5–15% clay by weight. Since this required sandy material is expensive and research elsewhere would suggest that a specific clay percentage is not required, the objective of this research was to test the validity of the clay content requirements and the effect of sand mineralogy on septic tank effluent renovation.Limestone, sandstone, and shale sands were used with clay added to give 0, 3, 6, and 12% clay. Septic tank effluent was applied at the rate of 1.5 cm/day to the surface of each sand‐clay mixture for 23 weeks. The effluent was analyzed at regular intervals before and after flowing through 60 cm of the sand for the following 16 chemical and biological variables: pH, chemical oxygen demand (COD), fecal coliforms, fecal streptococci, total Kjeldahl N, NH4‐N, NO2‐N, NO3‐N, (NO3‐NO2)‐N, PO4‐P, total P, Cl, Ca, Na, K, and specific conductivity. All the sand‐clay combinations (including the 0% clay samples) removed over 99% of the fecal coliforms and streptococci. The removal of P and COD and the transformation of N were highly efficient in the limestone and shale sands regardless of clay content. Renovation in the sandstone sand, which is a relatively inert material, was increased by the addition of small amounts of clay. It was concluded that sand type influences the renovation of effluent and is more important than the amount of clay. The results of this study indicate that limestone is the most desirable sand type, although long‐term dissolution may be a problem, followed by sandstone with a small percentage of clay, and then by shale. Although shale was a relatively efficient renovator of effluent over the time period studied, it is anticipated that the susceptibility of shale to weathering would lead to early clogging.

Physical and Chemical Methods of Water Renovation

AbstractThe paper deals with the effectiveness of secondary effluent renovation with iron, alum and dolomite coagulation, electrocoagulation, adsorption on activated carbon, ammonia nitrogen removal on clinoptilolite.

Waste water renovation through soil percolation

A laboratory experiment simulating high-rate effluent renovation by soil percolation involved leaching secondary sewage effluent through columns of three differing soils. Analyses of P in 22 leachate collections and distribution of both organic and inorganic P in column sections revealed the mechanisms of P removal, the influence of differing soil properties, and the effect of continuous utilization. Renovation of effluent P was greatest with percolation through columns of acid Milner soil which contains abundant Al and Fe, and, although Squilax soil removed more P from initial leachings due to its higher exchangeable Ca content, Glenmore soil was the more suitable of these two alkaline soils over the long term. The leachate N003-N levels were lower than the original N03-N content of effluent for the first ten leachings but N03-N enrichment occurred for the last effluent percolations through all three soils. Analyses of Ca, Mg, K, and Na in leachates and soil columns indicated losses of exchangeable cations from the calcareous Squilax and Glenmore soils enriched effluent content and the accumulation of the cations in the acid soil reduced concentrations in effluent that passed through Milner soil.

Use of Soil to Treat Anaerobic Lagoon Effluent Renovation as a Function of Depth and Application Rate

Use of Soil to Treat Anaerobic Lagoon Effluent Renovation as a Function of Depth and Application Rate