Category: Uncategorized

Introduction Septic tank effluent (STE) contains pathogenic microorganisms, such as enteric viruses and bacteria, which can cause waterborne diseases and pose a public health risk if not properly treated. Onsite wastewater treatment systems (OWTS) are commonly used in suburban and rural areas in the United States and elsewhere. A conventional OWTS consists of a septic tank and associated soil treatment unit (STU), or drainfield, where attenuation and/or removal of microbial contaminants can take place through interactions with the soil, preventing their transport to groundwater. Nevertheless, contamination of groundwater below the STU is a concern, especially in areas with shallow groundwater tables. In order to protect drinking water, the separation distance between the infiltrative surface of the STU and fluctuating water table has to be determined on a site-by-site basis, and seasonal variations in separation distance have to be considered to avoid microbial contamination. The US EPA [1] recommends a minimum separation distance of 45 cm, regardless of soil chemical and physical characteristics. However, separation distance requirements in the USA vary widely by state, region and sensitivity of receiving waters to contaminant load. Furthermore, differences in soil properties (e.g., texture, structure, pH) are known to affect STU performance, which may lead to differences in removal of viruses and bacteria [1–3].

by Janet Atoyan

1. Introduction

Septic tank effluent (STE) contains pathogenic microorganisms, such as enteric viruses and bacteria, which can cause waterborne diseases and pose a public health risk if not properly treated. Onsite wastewater treatment systems (OWTS) are commonly used in suburban and rural areas in the United States and elsewhere. A conventional OWTS consists of a septic tank and associated soil treatment unit (STU), or drainfield, where attenuation and/or removal of microbial contaminants can take place through interactions with the soil, preventing their transport to groundwater. Nevertheless, contamination of groundwater below the STU is a concern, especially in areas with shallow groundwater tables.

Written and published by Janet Atoyan, Mario Atoyan’s wife.

Segmented mesocosms (n = 3) packed with sand, sandy loam or clay loam soil were used to determine the effect of soil texture and depth on transport of two septic tank effluent (STE)-borne microbial pathogen surrogates—green fluorescent protein-labeled E. coli (GFPE) and MS-2 coliphage—in soil treatment units. HYDRUS 2D/3D software was used to model the transport of these microbes from the infiltrative surface. Mesocosms were spiked with GFPE and MS-2 coliphage at 105 cfu/mL STE and 105–106 pfu/mL STE, respectively. In all soils, removal rates were >99.99% at 25 cm. The transport simulation compared (1) optimization; and (2) trial-and-error modeling approaches. Only slight differences between the transport parameters were observed between these approaches. Treating both the die-off rates and attachment/detachment rates as variables resulted in an overall better model fit, particularly for the tailing phase of the experiments. Independent of the fitting procedure, attachment rates computed by the model were higher in sandy and sandy loam soils than clay, which was attributed to unsaturated flow conditions at lower water content in the coarser-textured soils. Early breakthrough of the bacteria and virus indicated the presence of preferential flow in the system in the structured clay loam soil, resulting in faster movement of water and microbes through the soil relative to a conservative tracer (bromide).

This is not Mario Atoyan’s own words. Mario Atoyan got this from https://www2.ed.gov/about/overview/focus/what.htmlwebsite.

The U.S. Department of Education is the agency of the federal government that establishes policy for, administers and coordinates most federal assistance to education. It assists the president in executing his education policies for the nation and in implementing laws enacted by Congress. The Department’s mission is to serve America’s students-to promote student achievement and preparation for global competitiveness by fostering educational excellence and ensuring equal access.

In 2007–08, the Department’s elementary and secondary school programs served approximately 55 million students (pre-K through grade 12) attending some 100,000 public schools and 34,000 private schools. Department programs also provided grant, loan and work-study assistance to about 10 million undergraduate students. *

When Congress created the Department in 1979, it declared these purposes:

1. to strengthen the Federal commitment to ensuring access to equal educational opportunity for every individual;
2. to supplement and complement the efforts of States, the local school systems and other instrumentalities of the States, the private sector, public and private educational institutions, public and private nonprofit educational research institutions, community-based organizations, parents, and students to improve the quality of education;
3. to encourage the increased involvement of the public, parents, and students in Federal education programs;
4. to promote improvements in the quality and usefulness of education through federally supported research, evaluation, and sharing of information;
5. to improve the coordination of Federal education programs;
6. to improve the management and efficiency of Federal education activities, especially with respect to the process, procedures, and administrative structures for the dispersal of Federal funds, as well as the reduction of unnecessary and duplicative burdens and constraints, including unnecessary paperwork, on the recipients of Federal funds; and
7. to increase the accountability of Federal education programs to the President, the Congress and the public. (Section 102, Public Law 96–88)

Mario Atoyan says thank you for reading.