Performance evaluation of onsite sewage treatment : Evaluation of current research

Efficient management of domestic wastewater is a primary requirement for human well being. Failure to adequately address issues of wastewater collection, treatment and disposal can lead to adverse public health and environmental impacts. The increasing spread of urbanisation has led to the conversion of previously rural land into urban developments and the more intensive development of semi urban areas. However the provision of reticulated sewerage facilities has not kept pace with this expansion in urbanisation. This has resulted in a growing dependency on onsite sewage treatment. Though considered only as a temporary measure in the past, these systems are now considered as the most cost effective option and have become a permanent feature in some urban areas. This report is the first of a series of reports to be produced and is the outcome of a research project initiated by the Brisbane City Council. The primary objective of the research undertaken was to relate the treatment performance of onsite sewage treatment systems with soil conditions at site, with the emphasis being on septic tanks. This report consists of a ‘state of the art’ review of research undertaken in the arena of onsite sewage treatment. The evaluation of research brings together significant work undertaken locally and overseas. It focuses mainly on septic tanks in keeping with the primary objectives of the project. This report has acted as the springboard for the later field investigations and analysis undertaken as part of the project. Septic tanks still continue to be used widely due to their simplicity and low cost. Generally the treatment performance of septic tanks can be highly variable due to numerous factors, but a properly designed, operated and maintained septic tank can produce effluent of satisfactory quality. The reduction of hydraulic surges from washing machines and dishwashers, regular removal of accumulated septage and the elimination of harmful chemicals are some of the practices that can improve system performance considerably. The relative advantages of multi chamber over single chamber septic tanks is an issue that needs to be resolved in view of the conflicting research outcomes. In recent years, aerobic wastewater treatment systems (AWTS) have been gaining in popularity. This can be mainly attributed to the desire to avoid subsurface effluent disposal, which is the main cause of septic tank failure. The use of aerobic processes for treatment of wastewater and the disinfection of effluent prior to disposal is capable of producing effluent of a quality suitable for surface disposal. However the field performance of these has been disappointing. A significant number of these systems do not perform to stipulated standards and quality can be highly variable. This is primarily due to houseowner neglect or ignorance of correct operational and maintenance procedures. The other problems include greater susceptibility to shock loadings and sludge bulking. As identified in literature a number of design features can also contribute to this wide variation in quality. The other treatment processes in common use are the various types of filter systems. These include intermittent and recirculating sand filters. These systems too have their inherent advantages and disadvantages. Furthermore as in the case of aerobic systems, their performance is very much dependent on individual houseowner operation and maintenance practices. In recent years the use of biofilters has attracted research interest and particularly the use of peat. High removal rates of various wastewater pollutants have been reported in research literature. Despite these satisfactory results, leachate from peat has been reported in various studies. This is an issue that needs further investigations and as such biofilters can still be considered to be in the experimental stage. The use of other filter media such as absorbent plastic and bark has also been reported in literature. The safe and hygienic disposal of treated effluent is a matter of concern in the case of onsite sewage treatment. Subsurface disposal is the most common and the only option in the case of septic tank treatment. Soil is an excellent treatment medium if suitable conditions are present. The processes of sorption, filtration and oxidation can remove the various wastewater pollutants. The subsurface characteristics of the disposal area are among the most important parameters governing process performance. Therefore it is important that the soil and topographic conditions are taken into consideration in the design of the soil absorption system. Seepage trenches and beds are the common systems in use. Seepage pits or chambers can be used where subsurface conditions warrant, whilst above grade mounds have been recommended for a variety of difficult site conditions. All these systems have their inherent advantages and disadvantages and the preferable soil absorption system should be selected based on site characteristics. The use of gravel as in-fill for beds and trenches is open to question. It does not contribute to effluent treatment and has been shown to reduce the effective infiltrative surface area. This is due to physical obstruction and the migration of fines entrained in the gravel, into the soil matrix. The surface application of effluent is coming into increasing use with the advent of aerobic treatment systems. This has the advantage that treatment is undertaken on the upper soil horizons, which is chemically and biologically the most effective in effluent renovation. Numerous research studies have demonstrated the feasibility of this practice. However the overriding criteria is the quality of the effluent. It has to be of exceptionally good quality in order to ensure that there are no resulting public health impacts due to aerosol drift. This essentially is the main issue of concern, due to the unreliability of the effluent quality from aerobic systems. Secondly, it has also been found that most householders do not take adequate care in the operation of spray irrigation systems or in the maintenance of the irrigation area. Under these circumstances surface disposal of effluent should be approached with caution and would require appropriate householder education and stringent compliance requirements. However despite all this, the efficiency with which the process is undertaken will ultimately rest with the individual householder and this is where most concern rests. Greywater too should require similar considerations. Surface irrigation of greywater is currently being permitted in a number of local authority jurisdictions in Queensland. Considering the fact that greywater constitutes the largest fraction of the total wastewater generated in a household, it could be considered to be a potential resource. Unfortunately in most circumstances the only pretreatment that is required to be undertaken prior to reuse is the removal of oil and grease. This is an issue of concern as greywater can considered to be a weak to medium sewage as it contains primary pollutants such as BOD material and nutrients and may also include microbial contamination. Therefore its use for surface irrigation can pose a potential health risk. This is further compounded by the fact that most householders are unaware of the potential adverse impacts of indiscriminate greywater reuse. As in the case of blackwater effluent reuse, there have been suggestions that greywater should also be subjected to stringent guidelines. Under these circumstances the surface application of any wastewater requires careful consideration. The other option available for the disposal effluent is the use of evaporation systems. The use of evapotranspiration systems has been covered in this report. Research has shown that these systems are susceptible to a number of factors and in particular to climatic conditions. As such their applicability is location specific. Also the design of systems based solely on evapotranspiration is questionable. In order to ensure more reliability, the systems should be designed to include soil absorption. The successful use of these systems for intermittent usage has been noted in literature. Taking into consideration the issues discussed above, subsurface disposal of effluent is the safest under most conditions. This is provided the facility has been designed to accommodate site conditions. The main problem associated with subsurface disposal is the formation of a clogging mat on the infiltrative surfaces. Due to the formation of the clogging mat, the capacity of the soil to handle effluent is no longer governed by the soil’s hydraulic conductivity as measured by the percolation test, but rather by the infiltration rate through the clogged zone. The characteristics of the clogging mat have been shown to be influenced by various soil and effluent characteristics. Secondly, the mechanisms of clogging mat formation have been found to be influenced by various physical, chemical and biological processes. Biological clogging is the most common process taking place and occurs due to bacterial growth or its by-products reducing the soil pore diameters. Biological clogging is generally associated with anaerobic conditions. The formation of the clogging mat provides significant benefits. It acts as an efficient filter for the removal of microorganisms. Also as the clogging mat increases the hydraulic impedance to flow, unsaturated flow conditions will occur below the mat. This permits greater contact between effluent and soil particles thereby enhancing the purification process. This is particularly important in the case of highly permeable soils. However the adverse impacts of the clogging mat formation cannot be ignored as they can lead to significant reduction in the infiltration rate. This in fact is the most common cause of soil absorption systems failure. As the formation of the clogging mat is inevitable, it is important to ensure that it does not impede effluent infiltration beyond tolerable limits. Various strategies have been investigated to either control clogging mat formation or to remediate its severity. Intermittent dosing of effluent is one such strategy that has attracted considerable attention. Research conclusions with regard to short duration time intervals are contradictory. It has been claimed that the intermittent rest periods would result in the aerobic decomposition of the clogging mat leading to a subsequent increase in the infiltration rate. Contrary to this, it has also been claimed that short duration rest periods are insufficient to completely decompose the clogging mat, and the intermediate by-products that form as a result of aerobic processes would in fact lead to even more severe clogging. It has been further recommended that the rest periods should be much longer and should be in the range of about six months. This entails the provision of a second and alternating seepage bed. The other concepts that have been investigated are the design of the bed to meet the equilibrium infiltration rate that would eventuate after clogging mat formation; improved geometry such as the use of seepage trenches instead of beds; serial instead of parallel effluent distribution and low pressure dosing of effluent. The use of physical measures such as oxidation with hydrogen peroxide and replacement of the infiltration surface have been shown to be only of short-term benefit. Another issue of importance is the degree of pretreatment that should be provided to the effluent prior to subsurface application and the influence exerted by pollutant loadings on the clogging mat formation. Laboratory studies have shown that the total mass loadings of BOD and suspended solids are important factors in the formation of the clogging mat. It has also been found that the nature of the suspended solids is also an important factor. The finer particles from extended aeration systems when compared to those from septic tanks will penetrate deeper into the soil and hence will ultimately cause a more dense clogging mat. However the importance of improved pretreatment in clogging mat formation may need to be qualified in view of other research studies. It has also shown that effluent quality may be a factor in the case of highly permeable soils but this may not be the case with fine structured soils. The ultimate test of onsite sewage treatment system efficiency rests with the final disposal of effluent. The implication of system failure as evidenced from the surface ponding of effluent or the seepage of contaminants into the groundwater can be very serious as it can lead to environmental and public health impacts. Significant microbial contamination of surface and groundwater has been attributed to septic tank effluent. There are a number of documented instances of septic tank related waterborne disease outbreaks affecting large numbers of people. In a recent incident, the local authority was found liable for an outbreak of viral hepatitis A and not the individual septic tank owners as no action had been taken to remedy septic tank failure. This illustrates the responsibility placed on local authorities in terms of ensuring the proper operation of onsite sewage treatment systems. Even a properly functioning soil absorption system is only capable of removing phosphorus and microorganisms. The nitrogen remaining after plant uptake will not be retained in the soil column, but will instead gradually seep into the groundwater as nitrate. Conditions for nitrogen removal by denitrification are not generally present in a soil absorption bed. Dilution by groundwater is the only treatment available for reducing the nitrogen concentration to specified levels. Therefore based on subsurface conditions, this essentially entails a maximum allowable concentration of septic tanks in a given area. Unfortunately nitrogen is not the only wastewater pollutant of concern. Relatively long survival times and travel distances have been noted for microorganisms originating from soil absorption systems. This is likely to happen if saturated conditions persist under the soil absorption bed or due to surface runoff of effluent as a result of system failure. Soils have a finite capacity for the removal of phosphorus. Once this capacity is exceeded, phosphorus too will seep into the groundwater. The relatively high mobility of phosphorus in sandy soils have been noted in the literature. These issues have serious implications in the design and siting of soil absorption systems. It is not only important to ensure that the system design is based on subsurface conditions but also the density of these systems in given areas is a critical issue. This essentially involves the adoption of a land capability approach to determine the limitations of an individual site for onsite sewage disposal. The most limiting factor at a particular site would determine the overall capability classification for that site which would also dictate the type of effluent disposal method to be adopted.

Assessment of the application of contingent valuation theory to bio-sequestered carbon

The issue of carbon sequestration rights has become topical following the United Nations Convention on Climate Change (United Nations 1992 at page 1414) and the subsequent Kyoto Protocol (United Nations Climate Change Secretariat 1998) which identified emissions trading as one of the mechanisms to reduce greenhouse gas emissions. Australian states have responded by creating a legal framework for the recognition of rights to bio-sequestered carbon. There is a lack of uniformity in the approach of each state to the recognition of these rights, which vary from the creation of new and novel interests in land to the adoption of more traditional rights such as a profit a prendre. Rights to bio-sequestered carbon are likely to have an impact on the utility, marketability, value and financing of rural land holdings. Despite the creation of the legal framework for recognition of rights to sequestrated carbon, there has been a delay in the introduction of a formalised carbon trading scheme in Australia. In the absence of an established carbon market, this paper addresses the applicability of contingent valuation theory to assess the value of bio-sequestered carbon rights to a rural land holder. Limitations and potential controversies associated with this application of contingent valuation theory are also addressed in this paper.

Public preferences for biodiversity conservation and climate-change mitigation: A choice experiment using ecosystem services indicators

Potential conflicts exist between biodiversity conservation and climate-change mitigation as trade-offs in multiple-use land management. This study aims to evaluate public preferences for biodiversity conservation and climate-change mitigation policy considering respondents’ uncertainty on their choice. We conducted a choice experiment using land-use scenarios in the rural Kushiro watershed in northern Japan. The results showed that the public strongly wish to avoid the extinction of endangered species in preference to climate-change mitigation in the form of carbon sequestration by increasing the area of managed forest. Knowledge of the site and the respondents’ awareness of the personal benefits associated with supporting and regulating services had a positive effect on their preference for conservation plans. Thus, decision-makers should be careful about how they provide ecological information for informed choices concerning ecosystem services tradeoffs. Suggesting targets with explicit indicators will affect public preferences, as well as the willingness of the public to pay for such measures. Furthermore, the elicited-choice probabilities approach is useful for revealing the distribution of relative preferences for incomplete scenarios, thus verifying the effectiveness of indicators introduced in the experiment.

新疆自然区划单元土地利用/覆盖分布图谱研究

Under the direction of Geo-informatic Tupu theory, based on comprehensive natural division in Xinjiang and 1:100000 land use and land cover vector data in 2000 from resource and environment database of CAS, the paper gave out some distribution Tupu of land resource types in different regions of Xinjiang. GIS tools such as ARCTOOLS and ARCV1EW were used to clip the unit of each natural division. Some useful conclusions were established. Then the lower reaches of Tarim River were selected as typical area to analyze the ecological environment evolvement from 2000 to 2004 since the beginning of ecological water delivering. The comprehensive space-time analysis provided a method to monitor the effect dynamically. The main contents of the thesis are listed as follows: (1) Similarities and differences between North Xinjiang and South Xinjiang, 6 second-classified regions and 37 third-classified regions. The conclusion of each region emphasized the percentage of area of main land types, characteristic description and distribution of cultivated land > woodlands grassland-, water area^ urban and rural land and unused land. (2) Thematic Tupu of each region. It concluded artificial oasis Tupu, the proportion between dense-grass% moderate-grass and sparse-grass, pattern of land resources and the land use degree. The artificial oasis mean cultivated land^ woodland^ urban & rural land and other construction land. The proportion of grassland disclosed the quality of all grassland and showed the development of them. Pattern of land resources and the land use degree gave out the detailed development direction and development degree of each region. (3) Ecological environment evolvement of the lower reaches of Tarim River. The effects of each ecological water delivering were compared.

Les quais de l'estuaire du Saint-Laurent, 1870-1930 : une étude en archéologie historique

On trouve sur les côtes de l’estuaire du Saint-Laurent des vestiges de quai dont la ressemblance mutuelle suggère leur contemporanéité. Les vestiges de ces «quais du gouvernement » relatent une importante conjoncture (1870-1930) caractérisée par l'intégration des localités côtières dans une économie interrégionale. Le quai, autrefois lieu d'interface entre la ruralité et le cabotage, devient pour l'archéologue une occasion de retracer les éléments entrant dans sa conception et sa réalisation. L’observation des éléments architecturaux permet de distinguer les traits architecturaux associés aux quais du gouvernement parmi l’ensemble des techniques de construction déjà employées dans l’estuaire au XIXe siècle.

La ocupación de áreas de manantiales en la región metropolitana de São Paulo: los mercados de tierras en las zonas rurales periurbanas

Las ocupaciones ilegales, vinculadas a los procesos especulativos del mercado de tierras, generan numerosas tensiones ambientales y sociales. Estos conflictos se ven reforzados por la debilidad de las instituciones y los choques de intereses entre los agentes económicos. La mayoría de los estudios sobre los procesos de ocupación de las zonas rurales periurbanas en el Estado de Sao Paulo,  Brasil, se basan en la suposición de que de la Ley de Protección de los Manantiales (LPM) se genera la caída de los precios de las tierras. En este contexto, el presente estudio aporta un análisis  de la urbanización de estas áreas en los manantiales de la región metropolitana de Sao Paulo, del control de la influencia de la LPM en las ocupaciones y de la depreciación/valorización de terrenos  ubicados en esa zona. Los resultados muestran que el comportamiento de los precios de las tierras agrícolas de los municipios pertenecientes a las cuencas hidrográficas de la zona no estuvo influenciado  por la LPM. La influencia predo  inante, en este caso, es la de las políticas macroeconómicas del plan real de Brasil.

Emissions de N2O i desnitrificació en sòls agrícoles i d'ecosistemes naturals. Factors de regulació

La major conscienciació actual dels problemes de pol·lució que acompanyen les pèrdues de N del sòl cap a l'atmosfera ha reorientat les investigacions cap a un coneixement més profund dels processos implicats en les emissions dels compostos nitrogenats que comporten un major perjudici des d'un punt de vista ecològic així com els seus principals factors reguladors. La creixent preocupació per l'increment de la concentració atmosfèrica de N2O és deguda a les seves interaccions amb la fotoquímica atmosfèrica i el balanç de radiació de la Terra ja que intervé en la destrucció de la capa estratosfèrica d'ozó, contribueix a l'efecte hivernacle i participa de la pluja àcida. Es considera que els sòls són la principal font de N2O atmosfèric. Al voltant del 90% d'aquestes emissions són d'origen biòtic; els principals processos implicats són la desnitrificació i la nitrificació. L'emissió del N2O produït a través d'aquests dos processos es caracteritza pels diferents nivells de regulació que presenta ja que depèn de la taxa dels processos, de la proporció de N canalitzada per cada procés cap a la producció de N2O i del seu consum dins el mateix sòl el qual està relacionat amb les dificultats en el transport cap a l'atmosfera. Això comporta una gran dificultat a l'hora d'aprofundir en el coneixement de les emissions de N2O del sòl cap a l'atmosfera i de la seva regulació. El desconeixement dels nivells d'emissió de N2O i de la importància de la desnitrificació així com de la seva regulació tant en sòls agrícoles com naturals de les nostres contrades és el principal punt de partida dels objectius d'aquest treball.

Evaluation of agri-environmental and forestry schemes with multiple objectives

The evaluation of EU policy in the area of rural land use management often encounters problems of multiple and poorly articulated objectives. Agri-environmental policy has a range of aims, including natural resource protection, biodiversity conservation and the protection and enhancement of landscape quality. Forestry policy, in addition to production and environmental objectives, increasingly has social aims, including enhancement of human health and wellbeing, lifelong learning, and the cultural and amenity value of the landscape. Many of these aims are intangible, making them hard to define and quantify. This article describes two approaches for dealing with such situations, both of which rely on substantial participation by stakeholders. The first is the Agri-Environment Footprint Index, a form of multi-criteria participatory approach. The other, applied here to forestry, has been the development of ‘multi-purpose’ approaches to evaluation, which respond to the diverse needs of stakeholders through the use of mixed methods and a broad suite of indicators, selected through a participatory process. Each makes use of case studies and involves stakeholders in the evaluation process, thereby enhancing their commitment to the programmes and increasing their sustainability. Both also demonstrate more ‘holistic’ approaches to evaluation than the formal methods prescribed in the EU Common Monitoring and Evaluation Framework.

PPG13 and the residential developer

This paper reviews the evidence in favour of the compact city and considers whether it is a viable policy option. Environmentalists, acadenics and politicians have all expressed strong support for the compact city as a basis for sustainable development. A review of the literature broadly confirms the claims made on its behalf, in particular that it is energy efficient and that it plays a crucial role in preventing rural land loss. It is further shown i) that there is nothing inevitable about the established pattern of urban dispersal, and ii) that although urban land is charaterised by a number of contstraints on development,it could in principle satisfy much of the projected demand for housing. Yet urban sprawl continues. Some of the reasons for this in the case of residential development are examined by comparing the residential development process with the principles of sustainable development. The general conclusion of the paper is that proposals for urban containment are likely to be strongly resisted by housebuilders.

Brexit or Bremain? Future options for UK agricultural policy and the CAP

The outcome of the UK’s referendum on continued EU membership is at the time of writing uncertain, and the consequences of a vote to remain (‘Bremain’) or leave (‘Brexit’) difficult to predict. Polarised views have been voiced about the impact of Brexit on UK agriculture, and on the nature and level of funding, of future policy. Policymakers would not have the luxury of devising a new policy from scratch. WTO rules and commitments, the nature of any future accord with the EU, budget constraints, the rather different perspectives of the UK’s devolved administrations in Scotland, Wales and Northern Ireland, and the expectations of farmers, landowners and the environmental lobby, will all impact the policymaking process. The WTO dimension, and the UK’s future relationship with the EU, are particularly difficult to predict, and – some commentators believe – may take years to resolve. Brexit’s impact on the future CAP is also unclear. A vote to remain within the EU would not necessarily assuage the Eurosceptics’ criticisms of the EU, or the UK’s perception of the CAP. Whatever the outcome, future agricultural, food and rural land use policies will remain key preoccupations of European governments.

Influência das principais commodities agropecuárias e de variáveis macroeconômicas sobre os preços da terra agrícola no Brasil

Este trabalho tem como proposta investigar como o preço de terras de uso rural no Brasil é afetado pelos preços e exportações das principais commodities agropecuárias, bem como por variáveis macroeconômicas, como taxa básica de juros, taxa de câmbio, taxa de inflação e disponibilidade de crédito agrícola. Para tal foram consideradas as produções agrícola de algodão, café, cana-de-açúcar (e seus principais produtos açúcar e etanol), milho e soja, a produção pecuária de carne bovina e a produção industrial de celulose de fibra curta com foco em sua principal matéria prima, os plantios reflorestados de eucalipto. Em linha com estudos anteriores, foi encontrada evidência empírica de que o preço da terra possui cointegração com algumas das variáveis agrícolas, pecuárias e florestais citadas, em especial em estados com maior vocação agropecuária e/ou para silvicultura. Quanto às variáveis macroeconômicas, apenas a taxa básica de juros apresentou cointegração com o preço de terras para todos os estados avaliados, taxa de câmbio e disponibilidade de crédito rural não aparecem como variáveis estatisticamente significantes. Conclui-se que, para estados com notável participação na balança comercial brasileira de produtos agrossilvipastoris, é possível obter um modelo de equilibro de longo prazo entre o preço da terra de uso rural e as variáveis destacadas acima, de modo que investidores do setor possam utilizá-lo como ferramenta de projeção no auxílio da tomada de decisão além de avaliar potenciais impactos no valor de seus ativos A inovação do presente estudo está em testar as hipóteses de cointegração para cada um dos estados da federação.

Agrofuel policies in Brazil: paradigmatic and territorial disputes

The expansion of agrofuel crops challenges us to rethink policies, territories, human agency, and the paradigms used to explain them. In Brazil, policies supporting the expansion of agrofuel crops and the intensification of agrofuel production are reorganising rural land use and undermining some forms of participation in the capitalist and family modes of production. To reflect on this new reality, we study peasant movement reactions, proposals, and territorial disputes with agribusiness. Using the Pontal do Paranapanema region of São Paulo state as a case in point, the paper analyses territorial disputes between expanding sugarcane plantations and agrarian reform settlements as well as biodiesel production projects developed by the Landless Workers Movement (MST) and the Western São Paulo Federation of Settlement and Family Farmer Associations (FAAFOP). It also analyses the agrofuel policies of other peasant organisations, including Via Campesina. The production of agrofuels has changed the processes of land acquisition and use by both agribusiness and the peasantry, provoking new insights into the nature of territorial conflicts and thereby stimulating the need to revise perspectives on the agrarian question in Brazil.

Desempenho operacional e energético de um trator agrícola em função do tipo de pneu, velocidade de deslocamento, lastragem líquida e condição superficial do solo: Leonardo de Almeida Monteiro. -

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Geoecologia da paisagem na avaliação do uso dos recursos Hídricos da parte inicial da bacia do Ribeirão das Posses - SP

Pós-graduação em Agronomia (Irrigação e Drenagem) - FCA

Estudo agroambiental de uma microbacia hidrográfica, visando sua sustentabilidade

Pós-graduação em Agronomia (Energia na Agricultura) - FCA