TECHNOLOGY

Costing tool for Septic tank design and estimate

Cost is a critical factor in infrastructure projects, directly influencing funding and investment decisions. In civil engineering, cost estimation primarily involves material and labor expenses, offering an approximation of the total investment required. Project planning cannot proceed effectively without accurate cost estimates.Cost estimates are typically carried out by an engineer or professional estimator and this process can take weeks to months, depending on the complexity of the project. Therefore, there is a significant need for a tool that reduces estimation time and enables professionals to estimate construction costs more efficiently, enhancing budgeting during the planning phase. The tool’s value would be further enhanced if it were user-friendly enough for non-technical or non-expert users.

The Costing Tool for Septic Tank Design and Estimation is an Excel-based tool designed to simplify the septic tank sizing and cost estimation process. The tool calculates the required size of a septic tank based on the number of users and the geographical region. It also provides structural options, allowing users to select from stone, brick, or concrete construction materials. Based on the chosen size and structure, the tool generates a Bill of Quantities (BoQ), estimating both material and labor quantities. Additionally, a rate analysis sheet has been included in the tool where users can input their own material and labor rates, enabling the tool to estimate the overall cost of the septic tank.

This tool also allows users to customize the septic tank dimensions, brick size, and even the type of soling based on site conditions and specific client requirements. It is particularly valuable for understanding the cost of a septic tank design according to the number of users and the type of structure selected.

The tool consists of six sheets:

1. Cover Page & Instructions: Provides an overview of the tool and step-by-step instructions for its use. 

2. Input Sheet: Users enter necessary details such as the number of users, structure type, soling type, and brick size. This sheet also allows for the customization of septic tank dimensions based on side conditions or specific requirements. 

3. BoQ Sheet: Displays the detailed quantity estimate, generated based on the user’s inputs. 

4. MLQ Sheet: Provides a breakdown of materials and labor quantities, offering clarity on the resources needed for septic tank construction. This sheet is especially helpful for non-technical users to understand the materials and costs involved in the project. 

5. Drawing: Includes drawings of the septic tank, featuring a plan view as well as longitudinal and transverse sections. However, the drawing is not to scale, it provides a conceptual representation. 

6. RA Sheet: Users enter the costs for materials and labor in this sheet, facilitating rate analysis and allowing for cost estimation based on user-specified rates.

The primary target audience for this tool includes both technical and non-technical professionals, such as planners, managers, engineers, property owners, investors, and consultants. However, it is particularly beneficial for planners, decision-makers, and investors. While the tool provides detailed quantity estimates, it is primarily intended for planning purposes and should not be used as the sole reference for final project implementation. It is expected that this tool will assist in forming a clear idea of the investment required for implementing septic tank, making it useful even for non-technical users who may be involved in the decision-making process.

Rain Water Harvesting

With the rising demand for water and the increasing challenges posed by climate change, droughts, and water pollution, water is becoming an increasingly a finite resource. Rainwater harvesting (RWH) offers a sustainable and cost-effective solution to address water scarcity by collecting, storing, and/or recharging rainwater for later use. This technique can be applied at various scales, ranging from individual households to large commercial and industrial projects.


Rainwater harvesting refers to a broad set of techniques for capturing and utilizing rainwater close to its point of origin. It is particularly advantageous in regions where high-quality freshwater sources, such as surface water or groundwater, are limited. The adoption of suitable rainwater harvesting technologies is crucial for effectively harnessing rainwater as a viable water resource.
People have been collecting and storing rainwater in containers such as buckets, tanks, ponds, and wells for centuries. Rainwater harvesting can be used for a variety of purposes, including crop irrigation, washing, cooking, and drinking.

The benefits of an RWH system include:

  • Simple installation, with local technicians able to set up the system with ease.
  • Low-cost operation and maintenance.
  • The physical and chemical properties of rainwater often exceed those of groundwater or surface water.
  • RWH helps raise the water table in wells and boreholes.
  • Provides a reliable water alternative during drought conditions.
  • Rainwater is a renewable resource with minimal environmental impact.
  • Reduces surface runoff, helping to control urban and flash flooding.
  • Mitigates soil erosion caused by surface runoff.
  • Alleviates land settlement issues caused by excessive water extraction.

However, there are some limitations of rainwater harvesting, including:

  • Due to temporal and spatial variation, rainwater harvesting may not always be a reliable water source.
  • Air pollution, particularly in industrialized areas, can compromise rainwater quality.
  • In certain locations, recharge may not be feasible due to soil’s low permeability.
  • RWH is not recommended in high lime concentration areas in the soil, as groundwater recharge in such areas may cause negative effects, as seen in regions like Pokhara.

ECOSAN

Waste management is one of the major challenges for developing countries like Nepal, where the waste generated is haphazardly dumped, is causing pollution to both surface and ground water sources. Consumption of contaminated water can cause various water borne diseases such as diarrhea, dysentery, typhoid, etc. The cases of water borne diseases are increasing, resulting in deaths of many children less than 5 years of age. Nonetheless, different technologies such as drainage systems, water treatment systems, sanitary landfill has been developed in various phases of time addressing these environmental and human health issues. But implementation of these technologies developed in the western countries demand huge investment and highly skilled man power mostly unavailable to developing countries. Therefore, 3 R Principal (Reduce, Recycle and Reuse) on waste management has been the most effective tool, providing ample opportunities to re-use of the waste as resources. Similar to woes of water resources, Nepals’ agriculture sector is also in grim situation. The excessive and continuous use of the chemical fertilizers for the higher production is not only deteriorating the soil fertility but also posing harm to human health. Instead, the use of natural fertilizers could best serve the need for sustainable farming and improve human health. In this context the concept of ‘Ecological Sanitation (EcoSan)’ has emerged as a solution to tackle both of these problems.

Nature-based Wastewater Treatment System

Although nature-based wastewater treatment system was introduced in Nepal in 1997. The water sealed toilets are mostly connected to various types of containment and it is estimated that about 11 percent of the population mostly living in urban areas are connected to sewer systems (MICS, 2019). Most of the wastewater is not treated at all and is discharged into nearby rivers. Kathmandu has a few wastewater treatment plant but they are not functioning properly either because sewer lines that are supposed to bring wastewater to the treatment plants are broken or the treatment plants are too complex and expensive to operate. In such circumstances, nature-based wastewater treatment can provide a simple, affordable and effective solution in cities particularly in small and emerging towns where availability of land is the big issue but difficult to bear the high amount of operation cost.

Having a centralized treatment plant to treat wastewater of cities may be expensive and more complicative particularly for the cities of scattered settlements. In that case, the wastewater coming out of each settlement can be treated through a separate treatment plant and this will be comparatively simple, effective and affordable than having single system for the cities. Thus, this is also known as decentralized wastewater treatment systems or DEWATS.

Nature-based treats small amounts of wastewater and requires low maintenance. It generally treats domestic wastewater originating from individual or settlements, institutions. Typical nature-based treatment systems pass through various treatment stages and comprise the following technical treatment steps.

Pre-treatment: Pre-treatment stage is to remove solid waste such as papers, clothes, plastics, sanitary pad, globe etc. from the wastewater. Grit and sand, oils and grease in this stage. Bar-screen is a pre-treatment technology. Depending upon the resource availability and level of treatment required, there are manual and mechanical as well as coarse and fine screening technology.

Primary Treatment : The primary treatment is the initial stage where technologies such as settler, sedimentation tank, septic tank or biogas settler are used to settle down heavy/settleable solids. Wastewater is treated up to 20-30 percent BOD and up to 60 percent of suspended solids. However, the major objective of this stage is to remove settable solids before entering the next treatment phase.

Secondary Treatment : This phase includes the addition of biological treatment to the plant for removal of biochemical oxygen demand (BOD) so that the effluent water improves the effluent quality. Secondary treatment can be achieved by applying aerobic, Anaerobic, Anoxic, and facultative Processes and can remove up to 85 percent of BOD. It primarily uses Anaerobic Baffled Reactor and Anaerobic Filter as secondary treatment technology.

Tertiary Treatment: The addition of tertiary treatment to the WWTP will ensure the quality of effluent at the highest. Construction Wetland (CW) and policing pond are used as the tertiary treatment technologies. There are vertical and horizontal flow constructed wetlands.

Drinking Water Treatment

SODIS (Solar Water Disinfection)

SODIS (Solar Water Disinfection) is a simple water treatment method relying on solar electromagnetic radiation and temperature to inactive pathogens. SODIS capitalizes on the UV-A radiation of the solar electromagnetic spectrum to a germicidal effect. Additionally, infrared radiation raises the water temperature which has a pasteurization effect. Research has shown that SODIS is more efficient in water containing high levels of oxygen. In order to achieve maximum saturation of the water with oxygen, the bottles are filled up to three quarters and shaken for about 20 seconds before they are filled completely to the brim.

Although water supply coverage has increased remarkably in Nepal, not much attention has been given to improve the water quality. Recurring outbreaks of water borne diseases and high numbers of patients being admitted to hospitals with water borne disease ailments indicates a need to public health status via improving water quality. Additionally, the low income community are more vulnerable to such diseases and the subsequent economic repercussions. Considering the above mentioned factoids, it is essential to promote simple, low cost and effective water treatment options.