CC BY
15
Scientific Research of the Union of Scientists in Bulgaria - Plovdiv, series B. Natural Sciences and Humanities, Vol. XVII, ISSN 1311-9192, International Conference of Young Scientists, 11 - 13 June 2015, Plovdiv
REMOVAL OF NITROGEN IN URBAN WASTEWATER TREATMENT PLANT IN SKENDERAJ- OPTIMIZATION OF THE PROCESS
Msc. FARUK HAJRIZI1*; Dr. SHEFQET RASHANI2; Dr. SPIRO DRUSHKU3 1Regional Water Company Mitrovica,2Faculty of Geosciences and Technology Mitrovica
3Faculty of Natural Sciences-Tirana, -Email: [email protected]
ABSTRACT
Wastewater Treatment Plant in Skenderaj is biological system of wastewater treatment consisting of primary sedimention tank or Imhoff tank, trickling filters and final sedimentation tank.Biological conversion of organic nitrogen into ammonia is called ammonification, since this process is very fast in our paper begin with ammonia. Our biological wastewater treatment plant is not designed for total nitrogen removal, however, continuously achieves reduction of total nitrogen and 30% lower concentration of ammonium flow of less than 16 mg NH4-N / L. Denitrification certain scale achieved by returning a nitrate-rich stream from the final sedimention tank in tricking filter and maintaining an adequate solids retetion time within the filter. Improving the degree of denitrification achieved by increasing the flow of recycling and keeping the measure for a certain time. This paper aim is to describing the approach of the operation of this plant to trickling filter plant draining to achieve nitrification and denitrification in conformity with European standards for the discharge of wastewater. Optimalizimin of this approach we have demonstrated through studies conducted in our plant by comparing analysis results their before and after our intervention in fphysic settings. These results show a significant improvement in nitrogen removal by maximizing the life of existing infrastructure assets.
Keywords
Trickling filters, effluent recycle, Imhoff Tank, denitrification, biological nitrogen removal
INTRODUCTION
The Wastewater Treatment Plant in Skenderaj was built in 2011, it is the biological system of wastewater treatment consisting of primary sedimentation tank or reservoir of Imohoff, trickling filters and final sedimentation reservoir. The plant, although not designed to remove the nitrogen, however, continuously reaches reducing total nitrogen and 30% lower concentration of ammonium flow of less than 16 mg NH4-N / L. Through recycling nitrate-rich flow from filters final sendimentues reservoir drainage and maintaining a suitable time of suspension within the filter, the current plant will reach a considerable degree of denitrification. In this paper we will try by laboratory datacand intervention in process parameters have attempted to meet legal restrictions on the discharge of nitrogen loads that will fulfill the required boundaries of European
Standards.
To better understand the mechanism of nitrogen removal (excluding cellular assimilation) in wastewater treatment plant in Skenderaj was sampled and tested to measure the nature BOD5, COD, N. Side of the filter keeps draining almost all recycled nitrate after being depleted by the final sendimentues reservoir and has been a significant breakdown of organic particles and total nitrogen. This suggests that biological treatment (by ordinary heterotrofet and denitrifiers optional) and sedimentation processes of solids are carried out within a single reservoir.
METHODOLOGY AND MATERIALS
The process of wastewater treatment plant in Skenderaj is a biological system of wastewater treatment comprised the introduction of mechanical grill, a Imhoff sedimentation tank, trickling filters with plastic media, a final sendimentues tanks, sludge thickening and finally by for sludge drying beds (process flow schematic diagram shown in Figure 1). Influence of wastewater from collecting collector entered through metal grill pumps station that send their substrate in sedimentation Imhoff tank is a powerful and effective colon that causes a reduction of suspended solids of 50 to 70% while the rezeravar in our plant brings the reduction of solid substances up to 78%, reduce COD from 25 to 50%. and BOD5 90 to 99%.The rest of which has not been treated passes into the trickling filters. Wastewater treatment process with trickling or biofiltra filter has the ability to perform the following functions; (1) The conversion of ammonia to nitrites and then to nitrates, and finally to nitrogen gas, (2) removes BOD, (3) adding oxygen, (4) removes the carbon dioxide, (5) removes excess nitrogen and other gases inert, (6) removes turbulence and makes water clarity and (7) the removal of various organic pollutants.
Trie klinu I'M III.
^rt'pndii?. ; ijnlitr
i pr.hirtl naif si
^L'tirrar nf LrrilrarnL in
Klirnfrmj
Figure 1. The process of wastewater treatment in Skenderaj After secondary treatment (biological) through filters draining, the flow passes in the final final sendimentation tank where most biological materials are deposited as sludge, while the clear flow passes the pipe to discharge effluent into a river Drenica. A portion of the sludge from the final sendimetues reservoir also requires special treatment to achieve the required standards and can be combined with the primary sludge for this purpose. This porces of wastewater treatment through trickling filters performed through biological degradation of organic material by bacteria and microorganisms that are found in the layer of draining filter media, the organism largely reduce the biochemical oxygen demand (BOD) of the wastewater; however, they also can be used to reduce ammonia nitrogen (NH3-N) through the process of „nitrification". Nitrification is the biochemical oxidation of ammonia nitrogen (NH4 +) to nitrate nitrogen (NO3-) by bacteria autotrophic aerobic conditions. There are two important types of bacteria on nitrification and they are Nitrosomones, which convert ammonia to nitrite (NO2-), and Nitrobakteriet, which convert 46
nitrites to nitrates.
Other types of nitrification bacteria include Nitrosospire, Nitrosolobus, and Nitrosovibrio. Those nitrification bacteria are slow growing organisms, and for this reason are particularly sensitive to toxic substances, however, they are able to adapt to toxic substances which are constantly present (Halling-Sorensenand Jorgensen, 1993).
N+ 3/202 -> JV02" + 2H~ 4- /S2S>
or
nitro—bacteria
JV02" +l/202 -h iV03-
Two steps reactions are usually very fach and so is rare phenomenon that nitrhes to find higher than 1.0 mgcl in water. Nitrate is fo rmed by nitrification, nitrogen cycle, which is used by plants as
a source of nitrogen or reduced to N, gas intended denitrification process.
In trickling filters, nitrification bacteria grow in a polluted layer or film attached to a solid media. Many type s of medir pe used in trickling filters, including stone s, pSastic rings random, prlyethyle ne strip si ayd sheels of eyrsugated plastio. Plastic media, which are commonly used in modern tankting filters as is ours in Ske^na], they fall into two classifications, -aortica! and cross flow; both of them, media streams hybrid (cross) leas a transfer more effectiaeiy with high oxygen and a highe r time between bksfilm and poocess liquid, ond therefore is preferred for nitrification mstems.
Nitrification aate achieved in trickling filtero dependa on a nnmbee of factors, including BOD5 loading rate, temperature, dislolaed oxygan concenteation, canrentration oB ammonia, pH and alkalinity oo the procms liquid, maoy of the factors aqe inte r-related. In ltlfrh concentrations BOD5, factors ^Efi;c;tin-s nitriiicftion in trickli^ filters include fydranlic Hodlng, ]:Lyc^aulic model and time o° fi0:er medin, ihi^ concentration of dissolved oxygen in liquid process, pH, temperature, concrntration of total nitrogen and BOD conrentoation. Empirisal deslgn curves fo:^ nitrification in trickting f:Ll^ers shouM include pneametens fol" hydraulic loading, molding ammonia c oncentration, tlm efferts of recycling, and wastewater temperature.
Ouo work is a study OssO deoe mines the amount of demtrification potentM in the wastewater treatment plant In s"kenderat by increasmg the flow of recyctiyg of tlle fina reservoir sendimentues trickling filite rjs^ NttГ^lтofIe n mass nalance oi" solids are closed lo supposO the understanding of imno rtihnf mechanisms old tile process, dt Oosls also Is een desc uSed by field trials was that the control of sludge retention time wlthim the filter tank drainnge is an importnat measure to achieve the desired pelOttlfrnace delktrificatinn. The resnltls of this stydy cso Sre nsell to evaluate the potential of deaitrification for stmilnr plantr гГnclnde plimarf sedimentation and effluent recycling.
3. RESULTS
By operating nitrified recycle more trickling filter effluent primary sedimentation tanks, over 60% of total nitrogen removal is accomplished through denitrification in ,activated' primary sedimentation tanks.
Suspension return from final sedimentation tank to trickling filters recycling reaches 45% , this recycling rate in wastewater treatment in Skenderaj reaches total nitrogen removal rate of 30% which fails; to meet the required standards by the European Union.
In oMer to determine tine additional amount of nitrate mobile through existing drainage filters, the experiment was designed to increase recycling flow from the reservoir so that the final sedimentation more tutn nitrate drattting filteos, except this time ws have analyzed residence flow filtere during 22014.
140 g20 100 80 60 6040 20 200
\
V --■---- y/
^^^ B ^^^..........
July August September October November ♦ recycling rate m3/h —№ nitrogen removal, % December
Figure 2. The ratio between the flow of recycling and removal of nitrogen % Besides comparing with the flow o:f recycling in this paper we parsed also another aspect that has to do with the timo of said solid stay in trickling filters, presedting experimental ce suits obtained in Figure 3.
70
M
1 2 3 4 5 6
% nitrogen removal
Figure 2. The ratio between the solidsretention time and removal of nitrogen %
During the six-month trials were analyzed incoming flow (from reservoir Imhoff and it's recycled) and exits during this period, focusing on the analysis of nitrogen removal from trickling filters.
4.CONCLUSION
From the results then achieved by ekspeimetet made note that increasing the level of recycling flow from the final sendimetare tank to trickling filter can increases the value of nitrogen removal. Further increase of the total removal of nitrogen may be available by applying high flow rate recycle if trickling adequate Filters can be maintained and hydraulic constraints are not violated.
Using Trickling Filter recycle flow in primary sedimentation tanks to achieve biological nitrogen removal is considered a novelty and represents a retrofit approach to cost-effectively meet more stringent restrictions exhaust flow. Significant savings on capital and operating costs can be achieved by reusing existing infrastructure where available and not simply the adoption of a conventional activated sludge approach.
Another achieved by increasing the level of recycling of nitrate is potential wind control and reduction in chemical use for odor control. Drainage filters scale plants usually produce H2S in sendimentues Imhoff tank through the reduction of sulfate present in the incoming entity (influentin) wastewater.
Restrictions trajtimite plant project in polluted waters that flow Skenderaj recycled to return the final reservoir sendimetues not trickling filter in the primary reservoir sendimetues not allow us sufficient improvement in nitrogen removal as it foresee environmental standards in force . If technical possibilities will allow us, in the time of day when the highest inflow and concentration of nitrates can be recycled by TFS power back to STEP, BOD5 sewage spill and soluble BOD5 concentrations can be relatively low, prevent full denitrification from occurring.
solids residence time in the trickling filter represents another analysis that we have done during this period of six months, according to experimental and analytical analysis could conclude that stay longer in trickling filter also means increasing the percentage of nitrogen removal.
5. REFERENCES
Richard Sedlak. (1991), Phosphorus and Nitrogen Removal From Municipal Wastewater,Princ^les und Practice, Second Edition
Dorias B. and Baumann P. (1994). Denitrification in trickling filters. Water Science and TecOorlrgy, 30(6), 81-184.
Gambrill, M. P. (1990) 'Physicochemical treatment of tropical wastewater', PhD thesis,
University of Leeds, Leeds
Pearce P. (2004).Trickling filters for upgrading low technology wastewater plants for nitrogen removal. Water Scienceand Technology, 49(11-12), 47-52.
Mehlhart G. F. (1994). Up grading of existing trickling filter plants for denitrification. WaterScience and Technology, 30(6), 173-179.
Pearce P. (2004).Trickling filters for upgrading low technology wastewater plants for nitrogen removal. Water Science and Technology, 49(11-12), 47-52.
http://www.ebsbiowizard.com/2010/10/nitrification-support/
