Programmable logic controller-based automatic control for municipal wastewater treatment plant optimization

The treatment of industrial wastewater can effectively protect the water environment and maintain sustainable development. This paper introduces an incremental proportion and integration (IPI) control algorithm-based programmable logic controller (PLC) used to adjust the aeration tank's dissolved oxygen content automatically in the wastewater treatment process. The control algorithm was improved by a back-propagation neural network (BP-NN). An instance analysis was carried out on a wastewater treatment plant in Zhejiang Province, China. This showed that the BP-NN improved control algorithm made the aeration tank's dissolved oxygen content more stable at the set value than it was with manual adjustment and the conventional algorithm. The total nitrogen content in wastewater treated in the aeration tank under the control of the improved IPI algorithm was minimized and fluctuated least. The aeration tank blower's power consumption was also at its lowest under the control of the improved IPI algorithm.

Penyisihan Material Organik dan Nitrogen dengan Proses Aerasi Menggunakan Microbubble Generator (MBG) pada Instalasi Pengolahan Air Limbah (IPAL) Asrama

Sebuah Instalasi Pengolahan Air Limbah (IPAL) di asrama mahasiswi UGM, Yogyakarta memiliki unit reaktor yang terdiri dari ekualisasi, aerasi 1, aerasi 2 dan clarifier dengan proses aerasi secara intermiten menggunakan Microbubble Generator (MBG) dengan fase aerasi dan tanpa aerasi masing-masing selama 15 menit. IPAL tersebut dibangun sebagai upaya dalam memenuhi standar Green Building bagi bangunan lama asrama di UGM untuk mengolah air limbah grey water. Hasil olahan air limbah akan dimanfaatkan di lingkungan asrama. Selama 208 hari beroperasi, kajian mengenai performa IPAL belum pernah dilakukan. Oleh karena itu, diperlukan kajian untuk mengetahui performa dan konsumsi energi pada IPAL dalam menyisihkan parameter pencemar berupa COD, nitrogen dan fosfat. Kajian dilakukan selama 81 hari pengamatan dengan menguji parameter kualitas air limbah pada setiap unit pengolahan. Parameter COD dan amonia telah memenuhi baku mutu Peraturan Menteri Lingkungan Hidup dan Kehutanan No. 68 Tahun 2016 tentang Baku Mutu Air Limbah Domestik, sedangkan parameter fosfat masih belum memenuhi baku mutu Peraturan Daerah D.I.Y. No.7 Tahun 2016 mengenai kegiatan IPAL Komunal. Hasil pengamatan pada performa IPAL, menunjukkan kedua tangki aerasi memiliki performa yang hampir sama, namun keberadaan tangki aerasi 2 tidak memiliki pengaruh yang signifikan dalam menyisihkan parameter pencemar. Pada tangki aerasi 1, efisiensi penyisihan COD mencapai rata-rata sebesar 73,6±17,46%, penyisihan PO4-P sebesar 39,12±14,96%, penyisihan total nitrogen sebesar 56,15±19,6%, efisiensi nitrifikasi sebesar 73,1±20.07% dan efisiensi denitrifikasi sebesar 61,72±27,48%. Total konsumsi energi pada IPAL dengan proses aerasi intermiten, dengan debit rerata 537,84 l/hari sebesar 14,12 kWh/m3 dan biaya sebesar Rp. 20.414/m3. Urutan konsumsi energi terbesar adalah penyisihan fosfat sebesar 5,10 kWh/gPO4-P, kemudian penyisihan amonia sebesar 1,79 kWh/gNH3-N, penyisihan TN sebesar 1,95 kWh/gTN dan penyisihan COD sebesar 0,45 kWh/gCOD. ABSTRACTA Wastewater Treatment Plant (WWTP) in the student dormitory of UGM, Yogyakarta has a reactor unit consists of an equalization, aeration 1, aeration 2, and clarifier with intermittent aeration process using a Microbubble Generator (MBG) with or without aeration for 15 minutes each. The WWTP was built as an effort to meet the Green Building standards for the old dormitory at UGM to make better process of grey water. The processed wastewater will be used for the dormitory environment. Operated for 208 days, there was no former studies for the WWTP. Therefore, a study is needed to determine performance and energy consumption of the WWTP in removing pollutant parameters consisting of COD, nitrogen and phosphate. The study was carried out for 81 days of observation by testing the wastewater quality parameters in each treatment unit. COD and ammonia parameters have met the quality standards of the Regulation of the Minister of Environment and Forestry No. 68 of 2016 concerning Domestic Wastewater Quality Standards, while phosphate doesn’t meet the quality standards of Regional Regulation D.I.Y. No. 7 of 2016 concerning Communal WWTP Activities. Results shows the performance from two aeration tanks are almost the same, but the existence of aeration tank 2 doesn’t have a significant effect. The results in aeration tank 1 showed the COD removal efficiency reached an average of 73.6±17.46%, PO4-P removal 39.12±14.96%, total nitrogen removal 56.15±19.6%, the nitrification efficiency 73.1±20.07% the denitrification efficiency 61.72±27.48%. The total energy consumption with intermittent aeration process with an average discharge of 537.84 l/day is 14.12 kWh/m3 and a cost of Rp. 20,414/m3 with the largest energy use being phosphate removal at 5.10 kWh/gPO4-P, then ammonia removal at 1.79 kWh/gNH3-N, TN removal at 1.95 kWh/gTN and COD removal at 0.45 kWh/gCOD.

Pengaruh Sistem Aerasi Intermittent terhadap Removal Organik dan Nitrogen pada Pengolahan Air Limbah Domestik Kamar Mandi Umum

Sebuah instalasi pengolahan air limbah (IPAL) dibangun untuk mengolah air limbah greywater dan blackwater dari toilet dan kamar mandi umum Wisdom Park UGM yang terletak di Dusun Kuningan, Catur Tunggal, Sleman, Daerah Istimewa Yogyakarta. Unit reaktor proses IPAL tersebut terdiri dari sedimentasi, ekualisasi, aerasi 1, aerasi 2 dan secondary clarifier dengan sistem pengolahan berupa aerasi intermitten dan aerasi kontinyu dengan menggunakan Microbubble Generator (MBG) dan blower. Saat ini belum pernah dilakukan kajian terkait efektivitas sistem proses biologi pada IPAL dalam menurunkan kandungan organik dan nitrogen air limbah. Suatu sistem aerasi intermitten diaplikasikan dengan tujuan untuk mendegradasi kandungan organik dan nitrogen yang terkandung dalam air limbah, juga dapat meningkatkan dan meratakan suplai oksigen sehingga kemampuan penyerapan oksigen menjadi lebih besar. Evaluasi IPAL dilakukan selama 82 hari pengamatan dengan parameter air limbah yang diujikan terdiri dari COD, NH3-N, NO3-N, NO2-N, dan PO4-P yang nantinya akan dibandingkan dengan PerMenLHK No 68 Tahun 2016 tentang Baku Mutu Air Limbah Domestik. Hasil performa removal kontaminan di tangki aerasi 1 dan tangki aerasi 2 tidak jauh berbeda, sehingga menunjukkan bahwa pengolahan di tangki aerasi 2 tidak begitu efektif. Pada tangki aerasi 1 rerata removal COD sebesar 73,97±17,65%, removal PO4-P sebesar 53,31±13,72%, removal total nitrogen sebesar 1,57±164,29%, efisiensi nitrifikasi sebesar 82,26±16,47% dan efisiensi denitrifikasi sebesar -66,4±373,37%. Sedangkan, total konsumsi energi yang dibutuhkan untuk pengolahan air limbah di IPAL dengan debit rerata 82,06 l/hari sebesar 43,13 kWh/m3 dan biaya sebesar Rp 62.326,00/m3. Dengan konsumsi energi terbesar dihasilkan untuk peyisihan fosfat yaitu 2,99 kWh/gPO4-P, penyisihan total nitrogen sebesar 1,33 kWh/gTN, penyisihan ammonia sebesar 0,88 kWh/gNH3-N, dan penyisihan COD sebesar 0,7 kWh/gCOD. ABSTRACTA wastewater treatment plant (WWTP) was built to treat greywater and blackwater from the public toilets and bathrooms of Wisdom Park UGM located in Dusun Kuningan, Catur Tunggal, Sleman, Special Region of Yogyakarta. The WWTP process reactor unit consists of sedimentation, equalization, aeration 1, aeration 2 and secondary clarifier with a processing system in the form of intermittent aeration and continuous aeration using a Microbubble Generator (MBG) and a blower. Currently, no study has been conducted regarding the effectiveness of the biological process system in WWTPs in reducing the organic and nitrogen content of wastewater. An intermittent aeration system is applied with the aim of degrading organic and nitrogen content contained in wastewater, as well as increasing and leveling oxygen supply so that oxygen absorption capacity becomes greater. The WWTP evaluation was carried out for 82 days of observation with the tested wastewater parameters consisting of COD, NH3-N, NO3-N, NO2-N, and PO4-P which will later be compared with the Minister of Environment and Forestry's Regulation No. 68, 2016 on Domestic Wastewater Quality Standards. The results of the contaminant removal performance in aeration tank 1 and aeration tank 2 were not much different, indicating that the treatment in aeration tank 2 was not very effective. In aeration tank 1 the mean COD removal was 73,97±17,65%, PO4-P removal was 53,31±13,72%, total nitrogen removal was 1,57±164,29%, nitrification efficiency was 82,26±16,47%, and denitrification efficiency was -66,4±373,37% in aeration tank 1. Meanwhile, the total energy consumption required for wastewater treatment at WWTP with an average discharge 82.06 l/day is 43.13 kWh/m3 and a cost of Rp. 62,326.00/m3. Phosphate removal required the most energy, at 2.99 kWh/gPO4-P, followed by total nitrogen removal at 1.33 kWh/gTN, ammonia removal at 0.88 kWh/gNH3-N, and COD removal at 0.7 kWh/gCOD

CFD Simulation on Improving Water Quality based on Various Aerator Models to Demonstrate Cost Performance Analysis

There are many types of aerator that can be used to perform a water treatment process either from air to water or from water to air approaches. Other than focusing on the performance itself, the usage cost of aerator should be forecasted in detail too to have a sustainable and economical method in remediating the polluted water. Therein, the cost performance analysis was demonstrated by performing a computational fluid dynamics (CFD) simulation on improving water quality based on various aerator models. The simulation was focused in a small-scale aeration tank that consists of a mixing chamber, air duct, and a few of bubble diffusers. The improvement of water quality was assessed by calculating the number of gas bubble particles produced by 4 different configurations of aerator model, namely aerator model A, B, C and D, respectively. Results found that the aerator model D (5 bubble diffuser at 620 L/min) produces the highest number of gas particles up to 72.2%. However, the aerator model C (5 bubble diffuser at 300 L/min) was found to achieve the most efficient and sustainable approach based on energy consuming and cost of aerator configuration when compared to the other aerator models.

Comparison of Segmentation Performance of Activated Sludge Flocs Using Bright-Field and Phase-Contrast Microscopy at Different Magnifications

Activated sludge (AS) is a type of process which is commonly used for the treatment of sewage and industrial wastewater. In this treatment process, the settling of the sludge flocs is important to ensure the normal functioning of the system, while sludge bulking has become a common and long-term problem that greatly affects floc settleability. Thus, methods based on image processing and analysis are introduced for monitoring AS wastewater treatment plants. However, the effectiveness of using image processing methods heavily depends on the performance of segmentation algorithms. The AS wastewater plant can be monitored through microscopic images of the flocs and filaments. Water samples are taken from the aeration tank of the wastewater plants and then observed using bright field and phase-contrast microscopy to compare the segmentation accuracy at different magnifications i.e., 4x, 10x, 20x, 40x. In this paper, three methods to segment and quantify the flocs in bright field and phase-contrast microscopy images have been analyzed. The first method is image segmentation using Bradley local thresholding method, the second method is texture segmentation using range filtering and Otsu’s thresholding and the third method is Gaussian Mixture Method based segmentation. The experimental results show that Gaussian Mixture Model Method gives the best segmentation accuracy for bright-field microscopy and 10x magnification gives the best results.

Design flaws in compact plants for wastewater treatment in food industry enterprises

The results of adjustment work, carried out at the local sewage treatment plants of food industry enterprise are presented in this paper. The enterprise has two sites, designed for the treatment of high and medium concentration effluents with a low pH value (3.5-5.5). Concentrated effluents are treated under anaerobic conditions in a compact installation consisting of a waste receiver, an anaerobic bioreactor, centrifuge thickener, centrifuge, flocculant preparation units and reagents. Wastes of medium concentration after neutralization are treated under aerobic conditions. The structure of this compact unit includes first-stage flotators, aerotanks operating for incomplete biological treatment, and second-stage flotators. Foam of the first stage and excess activated sludge of flotation devices of the second stage are dewatered on filter presses without treatment. The essence of the commissioning work consists in a detailed analysis of design solutions for both sites, study of the wastewater composition of high and medium concentration, systematization of operational data, which will allow operation to select the optimal operating mode of the main structures (anaerobic bioreactor and aeration tank). On the basis of the performed work, the optimal technological scheme of the unit for anaerobic digestion of high-concentration effluents has been developed and proposed. It is recommended to abandon the use of reagents, introduced before the flotation devices of the first and the second stages, due to an increase in the working pressure in the saturator for a compact installation designed for the treatment wastewater of medium concentration.

Research on the effects of ferric salt added into aeration tank for phosphorus removal on biochemical system

In this paper, two iron salts, ferrous chloride (FeCl2) and ferric chloride (FeCl3), are directly added into an aeration tank for phosphorus removal, and their effects on the biochemical system are studied; the water quality parameters such as pH and alkalinity are also investigated. The extent of influence of the added iron salts on the pH and alkalinity of aerated solutions is demonstrated to be FeCl3 > FeCl2. When the dosage of iron ions is 20 mg/L, the decrease in pH and alkalinity caused by FeCl3 is 0.5 and 65 mg/L, which is higher than FeCl2 by 2% and 26%. The initial phosphorus removal effect of FeCl2 is worse than that of FeCl3, but after continued aeration and oxidation, the phosphorus removal effect of FeCl2 can be improved; however, the final phosphorus removal effect is basically the same as that of FeCl3 added directly. The results show that FeCl2 is preferred when iron salt is added directly into the aeration tank to remove phosphorus. The proposed scheme can reduce the effect of iron salts on the alkalinity of the biochemical system on the premise of ensuring the phosphorus removal effect of the system, and is conducive to ensuring the stable operation of the biochemical system.

Study on the Balance of Oxygen in Supply and Demand in Wastewater Treatment Plant

In order to accurately evaluate the comprehensive operation efficiency of aerobic biological treatment system in wastewater treatment plants (WWTPs), the process state aeration performance tester and the specific oxygen uptake rate online monitoring device were used to measure the oxygenation performance and the activated sludge performance in aeration tank, and the comprehensive operation efficiency of aerobic tank was evaluated by combining physical-chemical indexes and water quality analysis of the treatment system. The results showed that the oxygen transfer efficiency (OTE) of aerators under process state are reduced by 13.07% and 14.48% respectively compared with that in clean water in the No.3-tank and No.6-tank, and the aeration uniformity index (IAU) is 4.86 and 1.46 respectively. The oxygen uptake rate (OUR) in the third corridor decreased significantly, but dissolved oxygen (DO) was a high level. Oxygen in supply (Qs) was much greater than oxygen in demand (Cs), which have resulted a large waste of energy consumption. Finally, the subsection regulation strategy was proposed based on the principle of oxygen balance. The results of this study will not only help the WWTP to achieve energy-saving and consumption-reducing, but also stable operation.

Power Generation and Oxygen Transfer Analyses for Micro Hydro-Turbine Installed in Wastewater Treatment Aeration Tank

This study targets one of the major energy consumers in the U.S. It suggests a new mechanical system that can recover a portion of the energy in Wastewater Treatment Plants (WWTPs). The proposed system entails a hydro-turbine installed above the air diffuser in the aeration tank to extract the water-bubble current's kinetic energy and converts it to electricity. Observing the optimum location of the turbine required multiple experiments where turbine height varies between 35% and 95% (water height percentages above the diffuser), while varying the airflow between 1.42 L/s (3 CFM) and 2.12 L/s (4.5 CFM) with a 0.24 L/s (0.5 CFM) increment. Additionally, three water heights of 38.1 cm (15”), 53.4 cm (21”), and 68.6 cm (27”) were considered to study the influence of the water height. It was noticed that the presence of the system has an adverse effect on the Standard Oxygen Transfer Efficiency (SOTE). Therefore, a small dual-blade propeller was installed right above the diffuser to directly mix the water in the bottom of the tank with the incoming air to enhance the SOTE. The results showed that the maximum reclaimed power was obtained where the hydro-turbine is installed at 65% - 80% above the diffuser. A reduction of up to 7.32% in SOTE was observed when the setup was placed inside the tank compared to the tank alone. The addition of the dual-blade propeller showed an increase in SOTE of 7.27% with a power loss of 6.21%, ensuring the aeration process was at its standards.