Forbedring av koagulant-doseringskontroll i renseprosesser for vann og avløp

Chemical coagulation is one of the most important treatment processes in wastewater treatment and drinking water treatment. Defining the optimal coagulant dosage is a vital operation that decides the treatment efficiency and economy of the coagulation process. Chemical coagulation is a well-defined process where the optimal coagulant dosage is dependent on the influent quality, expressed by particle concentration, pH, temperature, colour or phosphate, alkalinity, etc. However, no conceptual model has been developed due to the complexity of this process and the research on coagulant dosage control has continued for decades (Ratnaweera and Fettig, 2015). Among all the avenues of research, the model predictive control based on online measurements is the most promising concept for coagulant dosage control. It presents various methods of model calibration and well-defined testing procedures. A Feed-Forward (FF) model based concept of a multi-parameter dosing control system for wastewater was originally proposed by Ratnaweera et al. (1994) and then improved upon by Lu (2003) and Rathnaweera (2010). According to previous results of full-scale tests, the multi-parameter dosing control system has proven to provide acceptable effluent quality and improved economy on most occasions in several wastewater treatment plants.Kjemisk felling er en av de viktigste enhetsprosessene i både avløps- og drikkevannsbehandling. Identifisering av optimal koagulantdose er sentralt i driften av koaguleringsprosessen, og avgjørende for både rensegraden og driftsøkonomien i prosessen. Kjemisk felling er en veldefinert prosess der den optimale koagulantdosen avhenger av kvaliteten på innkommende vann, gitt ved partikkelkonsentrasjon, pH, temperatur, farge eller fosfatinnhold, alkalinitet osv. Det finnes imidlertid ingen universielle konseptuell modell for å bestemme optimal dose ettersom prosessen er svært kompleks. Dette har ført til årtier med forskning på regulering av koagulantdosen (Ratnaweera og Fettig, 2015). Av de ulike forskningsretningene har prediktiv regulering basert på online målinger vist seg svært populært, og inkluderer forskjellige metoder for modellkalibrering og definerte testprosedyrer. Et konsept bestående av multi-parameter doseringsregulering for avløpsrensing ble opprinnelig foreslått av Ratnaweera et al. (1994) og forbedret av Lu (2003) og Rathnaweera (2010). Tidligere fullskala tester har vist at systemet for multi-parameter doseringsregulering gir akseptabel kvalitet på behandlet vann og forbedret driftsøkonomi i et antall avløpsbehandlingsanlegg.DOSCON A

Modeling Jar Test Results Using Gene Expression to Determine the Optimal Alum Dose in Drinking Water Treatment Plants

يعد التخثير من أهم العمليات في محطات تنقية مياه الشرب، ان استخدام مخثر الشبة يؤدي الى زيادة تركيز الألمنيوم المتبقي في المياه، والذي تم ربطه في العديد من الدراسات بمرض الزهايمر. لذلك فإنه من المهم استخدامه في الجرع الأمثل. في هذه الدراسة، تم إجراء أربع مراحل من التجارب لتحديد تأثير مواصفات المياه الخام، مثل: العكارة، pH، القلوية والحرارة على الجرعة الأمثل من مخثر الشبة  [   .14 O] للحصول على علاقة رياضية تمكن من الاستغناء عن الحاجة لتجارب الجرة. تم إجراء التجارب بظروف مختلفة وعلى مدى فصول السنة، وتم تحديد الجرعة الأمثل لكل دورة من التجارب لتشكيل نموذج يعتمد على التعابير الجينية.تم بناء النموذج عن طريق بيانات مواصفات المياه: العكارة، pH، الحرارة والقلوية للتنبؤ بقيمة جرعة الشبة الأمثل اللازمة، النموذج الذي تم الحصول عليه أعطى نتائج جيدة بمعامل ارتباط 0.91   ومربع جذر الأخطاء 1.8.  تمت مقارنة النتائج مع نموذج انحدار خطي والذي لم يكن كافيا لإعطاء نتائج جيدة نظرا لطبيعة العلاقة الغير خطية المعقدة.  سلاسل أخرى من التجارب تم القيام بها لتحديد الجرعة الأمثل اللازمة أثناء حدوث الفيضانات والتي تصل فيها قيم عكارة الى قيم عالية مع دراسة استخدام النشاء كمادة مساعدة للتخثير، تم الحصول على نموذج جيد للتنبؤ، بقيمة معامل 0.92 وجذر مربعات أخطاء   5.1.Coagulation is the most important process in drinking water treatment. Alum coagulant increases the aluminum residuals, which have been linked in many studies to Alzheimer's disease. Therefore, it is very important to use it with the very optimal dose. In this paper, four sets of experiments were done to determine the relationship between raw water characteristics: turbidity, pH, alkalinity, temperature, and optimum doses of alum [   .14 O] to form a mathematical equation that could replace the need for jar test experiments. The experiments were performed under different conditions and under different seasonal circumstances. The optimal dose in every set was determined, and used to build a gene expression model (GEP). The models were constructed using data of the jar test experiments: turbidity, pH, alkalinity, and temperature, to predict the coagulant dose. The best GEP model gave very good results with a correlation coefficient (0.91) and a root mean square error of 1.8. Multi linear regression was used to be compared with the GEP results; it could not give good results due to the complex nonlinear relation of the process. Another round of experiments was done with high initial turbidity like the values that comes to the plant during floods and heavy rain. To give an equation for these extreme values, with studying the use of starch as a coagulant aid, the best GEP gave good results with a correlation coefficient of 0.92 and RMSE 5.

Treatability of South African surface waters by enhanced coagulation

Abstract: The majority of South African inland surface water sources are compromised due to a long-standing national policy of mandatory return flows. With renewed emphasis on the removal of organic carbon in the latest SANS 241 water quality standard, many South African water treatment managers may need to consider adoption of enhanced coagulation (EC) in the near future to achieve both turbidity and NOM removal. From the study of 4 South African inland waters, this paper demonstrates that UV254 absorbance provides a more accessible, reliable and rapid way of monitoring NOM at treatment plant level. This report also provides a detailed procedure for determining the dosages for EC in terms of UV254 absorbance at jar test level. Using ferric chloride as coagulant, a correlation was established to estimate the coagulant dosage for any desired level of UV254 absorbance removal. This correlation enables a preliminary assessment of EC as a means of planned NOM removal. Should EC promise to be a candidate process for NOM removal, it should be verified at jar test level using the proposed procedure

Approbation of the texture analysis imaging technique in the wastewater treatment plant

publishedVersio

Effect Of Coagulant Recycling on Chemically Enhanced Primary Treatment Performance

Chemically enhanced primary treatment (CEPT) process is a promising method for carbon redirection and improving the performance and efficiency of wastewater treatment processes. CEPT is employed to precipitate colloidal and suspended matter from wastewater; however, this requires a significant amount of coagulant and produces large volumes of sludge. Coagulant recovery (CR) from the precipitated sludge has the potential to reduce sludge quantities, associated costs for disposal of sludge, cost of dosing fresh coagulant by regenerating and purifying the coagulant before reuse. This research was conducted to understand the feasibility and implications of CR in municipal wastewater. In order to evaluate the use of CR in municipal wastewater, recovery of aluminum and iron, which are the two most widely used coagulants, from primary sludge originated from coagulated raw wastewater and their reuse potential as secondary coagulant was investigated. The recovered coagulant which was obtained through acidification of the primary sludge, reused for treating primary wastewater and overall coagulation efficiency was determined as a function of the recovery cycles (two in number). While with fresh aluminum sulphate, the removal efficiencies of total suspended solids (TSS), chemical oxygen demand (COD), total phosphorous (TP), and total nitrogen (TN) were 85%, 65%, 80% and 33%, respectively, a drop in removal efficiency of TSS and COD was observed with recovered aluminum (85% to 60% and 65% to 50%, respectively). With fresh ferric chloride, 90% TSS, 77% TP, 62% COD, and 18% TN were removed from primary effluent, while with the recovered coagulant a decline in the TSS, COD and TN removal efficiencies and increase in their concentrations in effluent by approximately 10% occurred. Recoveries of both aluminum and iron declined with each cycle. Phosphorous was the most affected parameter with recycled coagulant, however, this could be precipitated as struvite at the end of the second cycle. Equilibrium modeling of various aluminum and iron species was conducted to determine the recovery potential of aluminum and iron at low pH. The chemical equilibrium modes predicted the formation of complexes like jurbanite, gibbsite for aluminum and jarosite, strengite for iron, which reduced the recovery. The effects of recycling of coagulant on various water quality parameters in the effluent were also determined. A preliminary operational cost analysis conducted on the recovery process demonstrated that the increased cost of acidification can be offset by the reduction in costs of fresh coagulant, dewatering and sludge disposal. Distribution of micropollutants (MPs) with fresh and recovered iron and aluminum in recovered coagulant and effluent was investigated. Based on their relative abundance in wastewater and range of octanol-water coefficients, 18 MPs from different groups such as antibiotics, food additives, surfactants were selected. The MPs were spiked into the influent from a primary stream collected from a local wastewater plant. The distribution of MPs in wastewater and the removal during coagulation were compound specific. MPs with log Kow ow \u3e2.5 were sorbed on the coagulated sludge. The distribution ratio (Kd) of all the MPs with log Kow \u3e2.5 was calculated and the extent of buildup on sludge due to repeated recycling was determined. Onlyow \u3e2.5 was being recycled with the recovered coagulant. This study thus alleviates the concern of building up of the MPs during recycle of the coagulants. Additionally, to assess the impact of CR on anaerobic digestion (AD), CEPT sludge, sludge obtained from use of recovered coagulants (recovered sludge), and the residual solids (spent sludge) after CR were subjected to AD at mesophilic conditions for 15 days. Approximately 52% destruction of volatile solids was observed for CEPT and recovered sludges, while for the spent sludge it was 47%. Both CEPT and the recovered sludge had similar methane formation potential reaching a maximum of 205 mL CH4/gCOD and the spent sludge could produce only 50 mL CH4/gCOD due to unavailability of organics. A chemical equilibrium model predicted the formation of vivianite and pyrite as iron-phosphorous (Fe-P) and iron-sulfur (Fe-S) compounds, respectively in the CEPT and recovered sludges formed during AD. This observation was key in determining that there was no difference in the Fe-P and Fe-S compounds formed in the CEPT and recovered sludges. The findings of this work demonstrated the potential of CR for wastewater and water treatment facilities for energy and cost saving

Eco-Efficiency of Drinking Water Treatment

Problem statement:In the water treatment processes, the chemicals (aluminum sulfate AS, chlorine, and polyelectrolyte) are required in the different steps of treatment (coagulation, flocculation, settling, disinfection…). The chemicals residues can affect the human healthy and the environment. The treatment process produces sludge according to the level of the water turbidity. However, the sludge management increases the monitoring expenses. Moreover, this water treatment sub-product constitutes a threat for the environment and the downstream water users.Approach:In this study, the effectiveness of chemicals uses and sludge reuse was evaluatedin order to find optimal operational conditions and reduce its residues. The influence of the chemicals consumption on the cost of treated water was also studied. A set of jar test experiments was conducted to find the sludge and aluminum sulfate dosages in order to improve the produced water quality for different turbidity levels. Results: Results demonstrated that the consumption of chemicals could be reduced by 10 to 15%. The sludge reuse improve the water quality and decrease the AS consumption by 50 to 60%. The turbidity removal is increasing and the aluminum residues is decreasing by 50%. Conclusions/Recommendations:Results show that the sludge reuse plays a very important role in reducing the aluminum sulfate dosage, improving the treated water quality and reducing water cost. The AS control and modeling reduce the chemicals consumption. This approach contributes in preserving the environment and opens income-earning opportunities for local population by promoting local products made from water treatment sludge

Palm oil mill effluent treatments and biomethane production using rice husk ash and palm kernel ash

Palm oil mill effluent (POME) is one of the major wastes in palm oil industry. Prior to the disposal, POME should be pretreated as it can reduce soil fertility and contribute to human health hazards. Until now, many approaches have been investigated to improve waste management of POME. Traditionally, sedimentation process is used for removal of suspended solids trapped in the water. However, one-step treatment only is unable to remove high amount of solids in shorter time. The use of coagulation-flocculation (CF) prior to sedimentation process helps to form proper flocs, thickened the volatile solid (VS) in the sludge and facilitate the sedimentation process. Based on previous work, numerous natural coagulants had been used in POME treatment such as chitosan, Moringa oleifera seed, rice starch and other novel biocoagulants. In this study, the potential of rice husk ash (RHA) and palm kernel ash (PKA) were assessed as natural coagulant. A comparison study between natural coagulants and aluminium sulphate (alum) were conducted using jar test. The optimum dosage, pH and settling time of each coagulant were investigated based on responses of chemical oxygen demand (COD) and total solid (TS). Response surface methodology was used to predict the removal efficiencies and optimum conditions for each sample. Results showed that, alum was capable to remove COD up to 52.36 ± 1.49 % and 84.94 ± 0.12 % of TS using 6.50 g of alum, pH 6.0 and 41.69 min of settling time. At optimum condition, 52.38 ± 0.85 % of COD and 83.88 ± 1.03 % of TS were removed using 6.00 g RHA, pH 3.6 and 57.00 min of settling time. Meanwhile, PKA was capable to remove 50.50 ± 0.97 % of COD and 80.64 ± 0.64 % of TS by using 7.14 g of PKA, pH 5.97 and 40.65 min of sedimentation time. The results showed that RHA and PKA had attained similar removal efficiencies of COD and TS as alum. The flocs produced from CF process were further tested for biogas production in 150 mL serum bottle. The test was done by using biomethane potential (BMP) assay to determine the effect of each coagulants used towards amount of biogas produced. BMP assay for RHA produced maximum amount of biogas (480.25 mL/gVS) within 36 days. The methane potential was 244.03 mL/gVS and the methane content in the serum from overall biogas produced was 66.71%. To predict the performance of biogas produced, first order kinetic model was selected as it is prevalently used to evaluate anaerobic digestion process from various substrates. The results obtained from kinetic study revealed that RHA possesed the highest kinetic constant, k = 0.0403. From this work, it is proven that RHA was better than PKA and it is capable to replace alum in POME treatment as well as good enhancer for biogas productions

Simultaneous nutrient and organic matter removal from wastewater by aerobic granular sludge process

Received: February 1st, 2023 ; Accepted: June 16th, 2023 ; Published: July 2nd, 2023 ; Correspondence: [email protected] granular sludge (AGS) technology offers several benefits, such as simultaneous removal of nutrients and organic matter from wastewater, stronger granule structure, excellent settleability, and high resistance to toxicity. However, the formation of granules can take a long time and needs to be dense and stable. In this study, the formation of aerobic granules in sequencing batch reactors (SBRs) using a granular activated carbon (GAC) and aluminium sulphate coagulant were evaluated for the simultaneous removal of nutrient (phosphorus (TP) and nitrogen (TN)) and organic matter (chemical oxygen demand (COD)) from wastewater. The reactors were continuously operated for 107 days and were fed with synthetic media and real domestic sewage. However, adaptation process with the synthetic wastewater led to relatively slow granulation process (sedimentation rate of sludge flocks was 3 m h-1 ). During the experiments, there was no visible formation of granules in SBRs based on the analysis of the sludge samples, only the formation of aggregate structures similar to flocks. However, the results showed that total phosphorus (TP) removal efficiency was over 90% in SBR operated with aluminium sulphate. However, COD and total nitrogen (TN) removals were higher in GAC SBR, 75% and 10%, respectively. Thus, even if granules are not developed yet, the system is working efficiently. The results of this study could be useful in the development of AGS technology for full-scale wastewater treatment plant