The Challenges and Opportunities of the Disposal of Biosolids at the Mangere Wastewater Treatment Plant by Reza Hendrawan
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Toward Sustainable Biosolids Management: The Challenges and Opportunities of The Disposal Of Biosolids At The Mangere Wastewater Treatment Plant By Reza Hendrawan Summary Auckland, as one of the world’s most liveable cities, is supposed to be able to manage their sanitation facilities, including biosolids, more wisely. Even though Auckland City has demonstrated their advanced processes in wastewater treatment, there is an issue on how to manage biosolids, a by-product generated during the wastewater treatment process, in a sustainable and integrated way. Evidence has shown that the application of biosolids can be harmful, not only to human health, but also to the environment. This report aims to re-evaluate current and forthcoming practice in disposing of biosolids from the Mangere Wastewater Treatment Plant. Currently, the biosolids are being disposed to rehabilitate an old oxidation pond, which seems to be in compliance with the standards set by The New Zealand Water and Wastewater Association. However it is a fact that the oxidation pond will be at full capacity shortly. With regard to this issue, Watercare has proposed to “rehabilitate” Puketutu Island by disposing biosolids into the quarry hole. Watercare’s proposal has attracted debates about the positive and negative effects of disposing of biosolids at Puketutu Island, which are discussed on this report. Even though the proposal has been granted by the Environmental Court, this report concluded that Watercare’s plan may be economically viable but should be seen as the last resort. It is further proposed that Watercare places more controls on industrial wastewater and restricts the type of waste that can be discharged into the sewerage system, especially wastewater which contains toxic metals. Unless metal contaminated input to sewers is banned, the quality of biosolids will stay beyond the standards and cannot be applied back to the land as fertiliser or land conditioner. 1 Introduction According to the annual Mercer Quality of Living survey in 2012, Auckland is considered as the world’s third most liveable city. The survey rank cities on categories such as political and social stability, socio- cultural environment, education, economic environment, housing, recreation, public services and transportation, and public health. Public health is a wide term that includes medical supplies and services, infectious diseases, air pollution and last, but not least, sewage and waste disposal. One of the main contributions that maintains Auckland’s public health is its state-of-the-art sewage and wastewater treatment system. The Mangere Wastewater Treatment Plant, which is located in the Manukau Harbour, South Auckland, treats 449 million litres of wastewater daily and serves more than 430,000 residential and business customers, or about 1.3 million people. Sanitation, including sewerage and wastewater treatment, is believed to be the greatest medical advance since 1840 (Mackenbach 2007). As shown by Mackenbach (2007), the importance of sanitation became known after the Western Europe Region had been attacked by several cholera pandemics between 1830 and 1860. A study showed that a 1% increase in expenditure on sanitation led to a nearly 3% decline in deaths caused by waterborne diseases such as diarrhoea, in American cities during 1902- 1929 (Cain, Rotella 2001). In less developed countries, access to sanitation infrastructure could reduce child deaths from diarrhoea by 2.2 million per year (Gunther, Fink 2011). Indeed, diarrhoea is the second largest cause of under-five mortality and 15 per cent of the total share of under-five mortality (Black, Cousens et al. 2010). In terms of economic loss, the lack of sanitation could have a severe impact. Indonesia, for example, losses about USD 6.3 billion annually due to poor sanitation (Napitupulu, Hutton 2008). This evidence signifies the importance of well-functioning sanitation facilities, especially for Auckland and its commitment to become the most liveable city in the world. Auckland’s wastewater treatment plant is managed by Watercare, an organisation that is wholly owned by the Auckland Council. Since it was upgraded in 2003, the Mangere Wastewater Treatment Plant has applied technology that reduces the treatment cycle of wastewater from 21 days to 13 hours. The plant uses primary (mechanical), secondary (biological) and tertiary (filtration and ultraviolet radiation) methods to treat wastewater from various sources and has the capacity to accommodate Auckland’s growing population for the next 30 years. With the current treatment processes, Watercare claims it can reduce odours and significantly improve the water quality going into the Manukau Harbour. Even though Auckland City has demonstrated their advanced processes in wastewater treatment, there is an issue on how to manage biosolids, a by-product generated during the wastewater treatment process, in sustainable and integrated way. Currently the Mangere Wastewater Treatment Plant receives wastewater containing organic, chemical and toxic substances as it transports domestic, commercial and industrial wastewater from the greater Auckland area. Wastewater characteristics have made it very difficult to treat as some heavy metal substances, for instance Zinc and Cooper cannot be removed completely during the process (Fitzmaurice, LeBlanc et al. 2007). The biosolids which contain such contaminants are very dangerous and could harm human health if they enter the food chain. There is evidence around the world where heavy metal substances have been found in human blood after consuming the meat from sheep and cattle that graze on contaminated land or fish from contaminated 2 rivers (McLaughlin, Parker et al. 1999, Järup 2003). Therefore, the application of biosolids as fertilizers should be limited into certain circumstances and require resource consent, as stipulated by the Resource Management Act (NZWWA 2003). As stated in the Resource Management Act, 1991, ‘every action requires sustainable management of natural and physical resources, including land, water, plants and animals’. Sustainable management is defined as ‘sustaining the potential of natural and physical resources to meet the reasonably foreseeable needs of future generations; safeguarding the life-supporting capacity of water, soil and ecosystems; and avoiding, remedying or mitigating any adverse effects of activities on the environment,’ (Resource Management Act. 1991). This report aims to re-evaluate current and forthcoming practice in disposing of biosolids. Specifically, it tries to answer four research questions. First, how are the biosolids from the Mangere Wastewater Treatment Plant managed? It then describes on going and planned practice in disposing of biosolids, while at the same time explains the rationale behind the practices. Secondly, is the current and future management of biosolids sufficient? It will identify the fitness of practice compared to the policy, rule and regulations as well as experience from other countries. Thirdly, what are the implications of the application of biosolids? It will outline the costs and benefits of the application of biosolids, including, but not limited to, environmental and economic effects. Lastly, how should the issue be managed to meet the sustainable management purposes and principles under the RMA? In order to answer the questions, scientific papers, reports, policy statements, guidelines, rules and regulations will be elaborated on, to discuss and compare the current practice on the application of biosolids in Auckland and other developed countries. Literature Review The New Zealand Water and Wastewater Association, or NZWWA (2003: 9), has defined biosolids as, “…sewage sludge or sewage sludge mixed with other materials that have been treated and/or stabilised to the extent that they are able to be safely and beneficially applied to land. Biosolids have significant fertilising and soil conditioning properties as a result of the nutrients and organic materials they contain.” According to the NZWWA’s Guidelines for the Safe Application of Biosolids to Land in New Zealand, the sludge from raw sewage, animal manure, food processing, and abattoir wastes are not considered as biosolids (NZWWA 2003). The guideline also set standards that have to be attained before the by-product of the wastewater treatment process can be considered as biosolids. Thus, the ‘sludge’ that does not meet with biosolids standards should be subjected to further treatment in order to meet those standards, or buried in a landfill facility (NZWWA 2003). There are some parameters that should be carefully assessed before the application of biosolids is made. Oleszkiewicz and Mavinic (2002) proposed five parameters to assess the risk of biosolids disposal and application; total solids content (TS), pathogen content, concentration of hazardous organic compounds, availability of suitable land for disposal, and heavy metals concentrations. Taking the Australian Environmental Protection Agency guidelines as a reference, Rawlinson (2012) suggested five 3 factors to be considered; buffer distances, soil contaminant concentrations, lands which are suitable or unsuitable to be applied by biosolids, and various biosolids contamination grades and management practices which need to be followed. The New Zealand Water and Wastewater Association (2003) proposes more than 16 criteria in order to assess the feasibility of the application of biosolids. However those criteria could be summarised into three points