By

Mohamed Elsofy Zain Elabedien Ezz Eldien

1- Prof. Dr.Y.Abd Elhameed Badr Department of laser with matter interaction, National institiute of laser enhanced science, cairo university

2-Dr.M.Samir Mousa Sanitary Engineering department, faculty of engineering,Helwan university, Elmataria

National Institute of Laser Enhanced Science, Cairo University, Cairo, Egypt

Microbiology lab manager, wastewater reference lab,  Holding company for water and wastewater

Abstract: in the area of water purification, nanotechnology offers the possibility of an efficient removal of pollutants and germs. Today nanoparticle, nanomembrane and nanopowder used for detection and removal of chemical and biological substances includes metals, nutrients, organics, viruses, bacteria, parasites antibiotics. Nonmaterial’s reveal good result than other techniques used in water treatment because of its high surface area (surface/volume ratio) (1) . The aim of this work is to study effect of silver nanoparticle Ag NPs before and after photofragmentation as coagulant and as disinfectant in wastewater; this has been carried out through flocculation, coagulation, and disinfection techniques. Flocculation has been carried out using silver nanoparticle; Coagulation has been dedicated using this material and disinfection also. Effect of each of the previous technique on PH, total dissolved solids, total suspended solids , biological oxygen demand, chemical oxygen demand ,total coliform  and fecal coliform . The optimum practical conditions for each technique and for the whole study have been selected.

Keywords:  Nanoparticles, photofragmentation, coagulant, disinfectant, biological oxygen demand, chemical oxygen demand.

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Introduction

The most of the countries are facing drinking water problems and countries are very severe especially in developing countries. The world is facing formidable Challenges in meeting rising demands of clean water as the available supplies of freshwater are depleting due to (i) extended droughts, (ii) population growth, (iii) more stringent health-based regulations and (iv) competing demands from variety of users.

(2, 3, 4).The River Nile, the longest river in the world, is the main source of irrigation in Egypt. Historically, Egypt’s rich agricultural land, with the exception of a few scattered oases in the desert, has consisted of the 1,200 km strip of the Nile River Valley and the Nile Delta. The annual per capita share of the country’s water resources is approximately 875 m³, of which 84 percent is crop water demand, with the consumptive use being nearly 68 percent. Estimation of the municipal water use depends on population growth rates, the consumption in liter/Capita/day, and distribution system losses

expressed as conveyance efficiency Estimation of Municipal Water use. From February to September, water released from the High Aswan Dam (HAD) for irrigation, Municipal, and industrial purposes is sufficient to maintain the required navigational draft in the Nile (5, 6, 7).

Everyone generates wastewater. Typical residential water usage is from 75 to 100 gallons per person per day. Seventy-three percent of the population is connected to a centralized (Municipal) wastewater collection and treatment system, while the remaining 27 Percent uses on-site septic systems. Water is not used up. When people are through with water it becomes wastewater—better known as sewage—that must be cleaned up before it is returned to the environment for reuse. In one way or another, all water is recycled. In the past, people had the idea that Wastewater was something that could be disposed of—it would just disappear. This idea has caused many people to assume that when they dispose of the wastewater they also dispose of any problems or hazards related to it. Today we recognize that we must recycle water to maintain sustainable supplies of safe drinking water for future generations. In order to clean up or treat wastewater for recycling, it is important to understand what Wastewater contains, what problems it may cause, and what it takes to clean it up. Chemically enhanced primary treatment (CEPT) is a wastewater treatment method that can also be used as an efficient preliminary step to biological secondary treatment (such as activated sludge and trickling filters). CEPT adopts the coagulation and flocculation processes and accomplishes a remarkable increase in the removals of common pollutants and contaminants such as BOD (biochemical oxygen demand), COD (chemical oxygen demand), and TSS (total suspended solids) present in the influent. In Egypt law 48 of 1982 necessitates secondary treatment of wastewater prior to disposal in water courses. This requires the achievement of relatively high levels of treatment. Secondary treatment (which is required to reach regulations limits) invariably uses biological treatment processes which require high operation and maintenance costs. Many types of chemicals have been studied as coagulants including alum, lime, ferric chloride and polymers. The main objective of the research is to investigate the effectiveness of the AgNPs controlled by laser (to different particles size) in wastewater line when used as coagulant in the measure of PH, conductivity, removal percent of BOD, COD, TSS, TVS, total and fecal coliform from municipal wastewater then study the effect of AgNPs (with different sizes) as disinfectant on total and fecal colifrorms removal percent.

Materials and methods

Freshly collected sewage samples were distributed among the six jars after thorough mixing. Coagulant dosage was then added in varying proportions in each jar followed immediately by the initiation of flash mixing, 100 RPM. After 1 minute, mixing was reduced to 30 RPM and held at this level for 20 minute. Finally, a quiescent settling period of 30 minute was allowed. At the end of the settling period, a sample of the supernatant was analyzed for the various parameters. Jar testing experiments were carried out using three samples one taken from the effluent of the  grit removal  from Abu Rawash  treatment plant (ARTP),  samples two of return activated sludge (RAS) and samples three  from effluent of  Zenin wastewater plant.

The specification of the instruments used for chemicals analyses are  the TSS, TVS, BOD, COD, Conductivity, PH, sludge volume index (SVI),Total coliform, Fecal coliform .

All experiments procedure According to procedure in standard methods for the examination of water and wastewater 20th Ed.(8)

Silver nanoparticles AgNPs preparation  :

preparation method  of AgNPs. (according to Borohydride – Creighton Method )(9)  used this chemical as follow:

Silver nitrate ( AgNo₃), Sodium Borohydride (NaBH₄), Sodium laureth sulfate.

The characterization of silver nanoparticles Prepared by NaBH₄

silver nps prepared by chemical method were investigated using UV-Visible spectrophotometer and Transmission Electron Microscope (TEM).  In previous work in our group we irradiated Ag NPs with 308 nm excimer laser. The maximum absorption and the full width at half maximum have been decreased as the number of pulses increased up to 100,000 pulses due to the size reduction. The Ag NPs irradiated with 308 nm excimer laser system see fig. (1)  .

silver nps prepared by chemical method were investigated again after irradiation with 100,000 pulses (plus) of excimer laser 308 nm using UV-Visible spectrophotometer and Transmission Electron Microscope (TEM). These nps had (have) different sizes.

The characterization of AgNPs (sample B)obtained by chemical reduction using NaBH4 is (in) given Fig. (2) . Fig.2(a) shows that the AgNPs are characterized by an absorption band at 409.5 nm. The average size of the AgNPs  is 21±5  as seen in Fig2 (b).

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