Community-based waste management strategies in relation to a targeted Nepalese community

Abstract

The Bagmati River, which is of great cultural and religious importance to the Nepalese people, is also a major water resource. Its degradation, as a result of urbanization and industrialization, affects water quality and poses a threat to the environment and to human health - as well as resulting in water scarcity. In particular, the discharge of sewage directly into the river without prior treatment contributes significantly to river water pollution, whereas municipal solid waste dumping onto the river bank and development activities are major contributors to the deteriorating situation of the river basin overall. This study addresses this problem from a number of perspectives including an examination of two appropriate community-based technologies that may contribute to the sustainable management of domestic waste and sewage and that will also minimize the impact on the surrounding environment, especially the Bagmati River. Thus an existing composting method, the Takakura Composting Method (TCM), for municipal solid waste management was scientifically investigated with a view to optimizing its current performance. Vermifiltration (VF), which exploits earthworm metabolism to remove contaminants from sewage effluent, was also scientifically investigated in order to develop its potential for treating domestic sewage at the community level. Also investigated is the potential for both of these technologies to be integrated into the community for resource recovery. In the context of this project, a community based eco-audit provided insight into the waste generation, power and water usage in a target community - namely: Ward Number 20 of Lalitpur Sub-metropolitan City, Lalitpur, Nepal. For this community, most of the households adopt a waste segregation method and already use the Takakura composting method to separate organic waste - in order to prepare compost at the household level. The survey revealed that 65 % of the waste is organic in nature. In terms of wastewater (domestic sewage, a combination of black and grey water) generation, each household generates an average of 200.6 L of wastewater per day, with the approximate average water use being 235.9 L per day; i.e. 85 % of water used is discharged as wastewater. However, none of the households treat wastewater on-site and the sewage water is collected from households through a system that discharges directly into the Bagmati River without any prior treatment. A pilot-scale three-layered biological Vermifiltration (VF) system, which consisted of distinct layers of soil, sand and gravel, was designed and constructed at City West Water’s sewer mining project site, the Sunshine Golf Course Treatment Plant, Victoria, Australia, where domestic sewage (as influent) could be accessed easily. The VF was assessed for its efficacy for the filtration of domestic sewage, as measured by the quality of the treated effluent. The unit was operated in two different Phases I & II (with soil type 1 & soil type 2 respectively). Water quality parameters such as temperature, pH, conductivity, dissolved oxygen (DO), biological oxygen demand (BOD5), chemical oxygen demand (COD), turbidity, total suspended solids (TSS), nitrogen content, phosphorous content, levels of heavy metals such as zinc, cadmium, mercury, lead and certain bacteria (E.Coli, Faecal coliform) were continuously monitored. The VF performance was found to be significantly effective in removing turbidity, TSS, COD, BOD5, NO2-N and NO3-N; with removal efficiencies of 87 %, 82 %, 41 %, 94 %, 84 % and 92 %, respectively, for Phase I. For Phase II, turbidity, TSS, COD, NO2-N and NO3-N removed by 83 %, 86 %, 52 %, 98 % and 93 %, respectively. The physico-chemical and biological profile of the system throughout the operation period demonstrated a significant removal of pollutants - especially suspended solids and organic matter. A pilot-scale Takakura composting system, analogous to a system that has already been implemented at the community level in developing countries, was constructed and scientific experiments were carried out with a view to optimizing its performance. Scientific research on this system, at this level and to this extent, has not been conducted before. At first, two different types of fermentation solutions (salt-based and sugar-based) were prepared utilizing locally available vegetable/fruit waste and fermented products. The physico-chemical parameters such as temperature, pH, conductivity, total organic carbon, nitrogen and the concentration of volatile fatty acids, lactic acid and ethanol were monitored with a view to optimizing the fermentation solutions (FS) with respect to time and substrate quantity. Then, three different compositions of seeding inoculates (SIs) were prepared utilizing the native microorganisms isolated in the FSs. Finally, three different TCM matrices (of compost) were prepared utilizing the three different compositions of SIs and the compost quality was assessed by monitoring parameters such as temperature profile, pH, conductivity, carbon-to-nitrogen ratio, available nutrients (nitrogen, phosphorus and potassium), micronutrients and trace metals - over 35 days. The compost maturity test involved four different methods - germination percentage, plant bioassay, C:N ratio and Fourier Transform Infrared (FTIR) spectroscopy. A new index was introduced to assess the health of test plants in terms of the number of leaves and height of the plant, termed the ‘Bushiness Index’ (BI). These studies revealed that the ideal FS could be obtained with a desired quality by varying time and substrate quantity. With respect to the quality of TCM matrices, the matrix with very high nutrient levels were found to be unfavourable for seed germination and seedling growth, which suggests that a too high a nutrient level in the compost could exhibit phytotoxic characteristics. However, when the same matrix was mixed with garden soil (GS), it was found that it imparts nutrients to the GS, which produced relatively healthier plants. The findings of this study showed that the TCM compost is “tunable” as required, which can be achieved by selecting the appropriate seeding inoculate. The study also supports the claim of the inventor that TCM is an innovative technology, which is simple, fast and easy to adopt at the community and household levels. Also of relevance to the appropriateness of the above technologies for this community is the current role and performance of the centralized Guheshwori Wastewater Treatment Plant (GWWTP), which is operated by the High Powered Committee for Integrated Development of the Bagmati Civilization (HPCIDBC). Therefore, this has also been investigated in terms of existing data records and constitutes part of the field work for this study. Notably, the river water monitoring at the point of discharge revealed that although the treatment plant itself satisfactorily treats the wastewater for discharge, operational requirements necessitate the mixing of the effluent and untreated influent through a by-pass, resulting in a net contamination of the river. Thus, a consideration of the data from the GWWTP, both existing and collected as part of this project, suggests that centralised conventional treatment systems such as GWWTP are not economically and technologically viable for a developing country like Nepal. This supports the adoption of alternative approaches such as the community-based Vermifiltration system studied here, as a means of more reliably ameliorating the discharge of wastewater into the river environment. Furthermore, the domestic wastewater effluent could be diverted for irrigation purposes. Similarly, solid waste management at the local level, through a method such as Takakura composting, could divert up to 65 % of organic waste that currently goes to landfill.