Small-scale Domestic Wastewater Treatment Research Articles

Additional Treatment of Nitrogen and Phosphorus Using Natural Materials in Small-Scale Domestic Wastewater Treatment Unit

The conventional wastewater treatment methods only remove up to 80% of total nitrogen (N) or phosphorus (P) from wastewater, so additional facilities are needed. This article describes a newly created other wastewater treatment unit (NCU) that increases the effectiveness of P and N removal of the small-scale biological wastewater treatment plant. This work aims to evaluate the capacity of simultaneous elimination from wastewater nitrogen (NH4-N, NO3-N) and phosphorus (PO4-P) by adsorption. NCU was filled with the sorbent material zeolite (clinoptilolite) and OCS (Fe, Mn, Ca oxides coated sand). After treatment in the main plant, wastewater flows through the NCU without using electric power. A compact system consisting of a main treatment plant and the NCU worked for 4 months, as the harmonized European Standard EN 12566-7 recommended. The NCU unit reduced PO4-P, NH4-N, and NO3-N concentrations in the effluent (74–98%, 52–99%, and 50–98%, respectively). In general, the small-scale system treated wastewater did not contain more than 1 mg/L phosphorus concentration and not more than 10 mg/L nitrogen concentration. This study demonstrates that treatment in NCU is an ecological and environmentally friendly method suitable for decentralized wastewater treatment.

Improving the efficiency of small-scale wastewater treatment by pneumatic agitation

Small-scale anaerobic and aerobic systems for wastewater treatment suffer relatively low efficiencies due primarily to a lack of mechanical agitation/mixing. Here, a pneumatic agitation system was designed by installing a U-tube between the anaerobic and anoxic units, pumping air to the closed headspace of the anaerobic unit and releasing the pressurized air through the U-tube to create turbulence of the fluid. Computational Fluid Dynamics (CFD) simulation and fluid tracer trial were used to describe the fluid status in a lab-scale system (13 L). The results demonstrated that a continuous 5-cycle pneumatic agitation achieved a complete mixing of the static fluid. The retention time factor ( β ) and short-circuiting flow coefficient ( t i /HRT) were increased from 0.93 to 1.14 and 0.02 to 0.27, respectively, indicating that pneumatic agitation significantly reduced dead zone and short-circuiting flow. A prototype at a treatment capacity of 300 L/d was installed in the North-East suburb of Beijing (40.15° N, 116.95° E) to treat rural household wastewater consisting of 630–1200 mg/L chemical oxygen demand and 20–45 mg/L total nitrogen. The field test was monitored in a period of 75 days from September to November 2018. The average removal rate for COD and TN was 96% and 92%, respectively by 10 times/h pneumatic agitation as compared to 49% and 45% without pneumatic agitation. The pneumatic agitation provides a low cost, easy operation and maintenance and efficient means for small-scale domestic wastewater treatment. • Pneumatic agitation improved the performance of small-scale wastewater treatment. • CFD simulation was applied to describe the process of the pneumatic agitation. • Fluid tracer trials were employed to analyze the hydraulic characteristics. • A prototype of 300 L/d was installed on-site to treat a rural household wastewater.

A Review of Phosphorus Removal Technologies and Their Applicability to Small-Scale Domestic Wastewater Treatment Systems

The removal of phosphorus (P) from domestic wastewater is primarily to reduce the potential for eutrophication in receiving waters, and is mandated and common in many countries. However, most P-removal technologies have been developed for use at larger wastewater treatment plants that have economies-of-scale, rigorous monitoring, and in-house operating expertise. Smaller treatment plants often do not have these luxuries, which is problematic because there is concern that P releases from small treatment systems may have greater environmental impact than previously believed. Here P-removal technologies are reviewed with the goal of determining which treatment options are amenable to small-scale applications. Significant progress has been made in developing some technologies for small-scale application, namely sorptive media. However, as this review shows, there is a shortage of treatment technologies for P-removal at smaller scales, particularly sustainable and reliable options that demand minimal operating and maintenance expertise or are suited to northern latitudes. In view of emerging regulatory pressure, investment should be made in developing new or adapting existing P-removal technologies, specifically for implementation at small-scale treatment works.

Feasibility of contact aeration method for small-scale domestic wastewater treatment system in rural China

This study examines the feasibility of the contact aeration method for utilisation in small-scale domestic wastewater treatment facilities in various rural areas of China, where the national government starts to address the water pollution issue. Three pilot facilities using the contact aeration method with different capacities were constructed, operated and monitored in Chongqing city and Jiangsu province. In order to evaluate the feasibility of the constructed facilities, the quality of treated wastewater and the operational cost were monitored. Results obtained from the monitoring showed that BOD and COD effluent concentrations achieved quality targets in all facilities. As for the other pollutants, quality targets were met for most of the period. Operational costs of facilities bettered those set for the facility in the town of Baiyang and new village of Zhaojia, but exceeded them for the facility in the village of Dongbei. The main reasons for the differences were the electricity billing system and operational system for each facility. In order to promote small-scale aeration-based domestic wastewater treatment plants in rural China in the future, the issue of what constitutes efficient facility maintenance first needs to be addressed.

Application of Iron Electrolysis to Full-Scale Activated Sludge Process for Phosphorus Removal

Addition of coagulant to the activated sludge process is an effective method to remove phosphorus from wastewater. Recently, iron electrolysis method has been developed as a new methodology of addition of coagulant into the activated sludge process. Although this process has been applied to industrial wastewater treatment plants or small-scale domestic wastewater treatment plants, the phosphorus removal performance by iron electrolysis combined with full-scale activated sludge process has not been clear yet. The objective of this study is to investigate the phosphorus removal efficiency by iron electrolysis combined with the activated sludge process. The enhanced biological phosphorus removal took place and phosphorus removal efficiency was increased without iron addition because of the occurrence of anaerobic condition in the surveyed wastewater treatment plant. Phosphorus removal performance in the investigated wastewater treatment plant was improved by the iron electrolysis. Effluent phosphorus concentration was decreased below 1.0 mg/L with additional iron of Fe/P molar ratio 0.4. The theoretical weight of iron release agreed with the actual weight decrease of iron electrodes. The introduction of iron electrolysis to the activated sludge process could enhance the phosphorus removal efficiency without any effects on substrate removal performance and make the phosphorus removal to be stable and sustainable.

Preliminary screening of small-scale domestic wastewater treatment systems for removal of pharmaceutical and personal care products

Occurrence and removal efficiencies of 13 pharmaceuticals and personal care products (PPCPs) as well as BOD 5, TSS and NH 4 + were evaluated for the first time in thirteen onsite household secondary wastewater treatment systems, including two compact biofilters followed by Filtralite-P filter units, two biological sand filters, five horizontal subsurface flow and four vertical flow constructed wetlands. As expected, all systems removed TSS and BOD 5 efficiently (>95% removal). The PPCP removal efficiencies exceeded 80% with the exception of carbamazepine, diclofenac and ketoprofen because of their more recalcitrant characteristics. Despite no statistical differences in the PPCP removal were observed between the different systems evaluated, the vegetated vertical flow constructed wetlands which had unsaturated flow and hence better oxygenation, appeared consistently to perform better in terms of PPCP removal efficiency. The combined effects of vegetation and unsaturated water flow provide a higher tolerance to variations in loading rate and a consistent removal rate.

Small-scale domestic wastewater treatment using an alternating pumped sequencing batch biofilm reactor system

An alternating pumped sequencing batch biofilm reactor (APSBBR) system was developed to treat small-scale domestic wastewater. This laboratory system had two reactor tanks, Reactor 1 and Reactor 2, with two identical plastic biofilm modules in each reactor. Reactor 1 of the APSBBR had five operational phases--fill, anoxic, aerobic, settle and draw. In the aerobic phase, the wastewater was circulated between the two reactor tanks with centrifugal pumps and aeration was mainly achieved through oxygen absorption by microorganisms in the biofilms when they were exposed to the air. This paper details the performance of the APSBBR system in treating synthetic domestic wastewater over 18 months. The effluent from the APSBBR system satisfied the European Wastewater Treatment Directive requirements, with respect to COD, ammonium-nitrogen and suspended solids. The biofilm growth in the two reactor tanks was different due to the difference in substrate loadings and growth conditions.

嫌気ろ床・生物ろ過法における物理化学的りん除去法導入による処理性能の評価

A simultaneous removal of nitrogen and phosphorus technology in small-scale domestic wastewater treatment was developed. Physicochemical phosphorus removal systems such as the coagulation method, electrolysis of iron method and electrolysis of aluminum method were combined with anaerobic filter bed-biological filtration process and removal efficiencies of organic matter, nitrogen and phosphorus as well as sludge generation were investigate.It was demonstrated that these systems improved the organic matter and phosphorus removal efficiencies. Moreover, the denitrification rate improved, which could contribute to stabilizing the nitrogen removal efficiency in this process, as well as reducing the volume of the anaerobic filter bed tank. The water quality of the effluent was less than BOD10mg⋅l-1, T-N10mg⋅l1 and T-P1 mg⋅l1. To achieve this efficiency with the coagulation method, it was necessary to closely manage the generated sludge. With the electrolysis of iron method, a high phosphorus removal efficiency was achieved under the general maintenance and management of generated sludge. With the electrolysis of aluminum method, although an extremely high removal efficiency was achieved, it was necessary to investigate the conditions for controlling the elution of aluminum ion to stabilize the phosphorus removal efficiency. These findings clarified that by incorporating the physicochemical phosphorus removal system with anaerobic filter bed-biological filtration process, the simultaneous nitrogen and phosphorus removal system could be established.

Characterization of microbial community in an activated sludge process treating domestic wastewater using quinone profiles

The dynamics of microbial community structure of activated sludges in a small-scale domestic wastewater treatment process were examined using a novel approach of quinone profiles. The composition and content of quinones in the activated sludges were analyzed monthly over a period of one year. More than 4 types of ubiquinones and 12 types of menaquinones were observed in the activated sludges, with the dominant quinones being ubiquinone (UQ)-8, menaquinone (MK)-7, followed by UQ-10, MK-8 and MK-6. The total quinone contents in the activated sludges varied from 0.93 to 2.68 mumol per gram of particle organic carbon. The molar ratio of ubiquinones to menaquinones (UK/MK) changed from 0.38 to 0.98, indicating that anaerobic bacteria dominated the microbial community of the activated sludges examined. The ratio of UQ/MK varied similar to that of dissolved oxygen in the bulk. The microbial diversity of the activated sludges calculated from the quinone compositions was 13.4-16.8. The diversity of menaquinones was much higher than that of ubiquinones, and increased slightly with increasing temperature. The microorganisms containing menaquinones appear to be sensitive to the change in temperature than those containing ubiquinones.

高度水処理技術における鉄電解法の応用

We examined phosphorus removal from small-scale domestic wastewater treatment system by means of an electrolytic bath. The electrolytic bath has electrodes of iron, and the wastewater treatment system has a biofilter. This method of removing phosphorus from the wastewater treatment system succeeded in removing more than 85% of the phosphorus while maintaining the Fe:P ratio at 1.5 and the polarity reversal period at 24 hours. And, this method offers high stability of phosphorus removal of more than six months. Moreover, compared with other methods, this method provides the phosphorus removal unit features a compact design and low running cost.In view of these facts, we believe that phosphorus removal technology incorporating the electrochemical elution of iron can be provided for any wastewater treatment system.

リン除去技術における鉄電解法の最適電解条件の検討

Phosphorus removal from small-scale domestic wastewater treatment systems by means of an electrolytic bath using of iron electrodes was examined.We discovered, however, that an iron oxide layer forms on the surface of the iron electrodes, leading to a decreased phosphorus removal ratio.To solve this problem, we discovered that specific electrolytic conditions can inhibit the formation of this iron oxide layer (FeOOH, Fe3O4) on the iron electrodes. One condition is the Fe:P ratio. An Fe/P ratio exceeding 1.5 inhibits the formation of this iron oxide layer. Another condition is the concentration of nitrate ions and nitrite ions. We have shown that the iron oxide layer forms when the nitrate nitrogen concentration is 60mg · l-1 or the nitrite nitrogen concentration is 10mg · l-1. However, a polarity reversal period of 24 hours inhibits the formation of the iron oxide layer when the nitrate nitrogen concentration is 60mg · l-1 and the iron oxide produced by nitrate ions and nitrite ions is broken down by the chloride ion at a concentration exceeding 60mg · l-1.

An Improvement of an Oxidation Ditch Process for the Low Alkalinity Wastewater Treatment and Various Influent Conditions

The oxidation ditch process (OD) had been propagated for small scale domestic wastewater treatment through the 1960s in Holland, by the benefits of capital and maintenance cost and easy maintenance. But it was not suitable for large scale plants due to the wide area and maintenance problems at the beginning. After that, the process spread through European countries and all over the world in conjunction with improvements in the equipment and the system. In the early stage in Japan, OD plants frequently experienced pH decline problems from low loading and excess aeration, as the alkalinity of domestic waste water in Japan is less than that of western countries. In this paper, a one-point aeration ditch process, developed by using a down-pumping submerged-turbine aerator, is introduced. The formation of an aerobic zone and an anoxic zone in the ditch is confirmed, and it is reported that the pH decline problem is solved by the effective, concurrent nitrification and denitrification in the ditch, with an indication of the alkalinity balance. Furthermore, new preparations and improvements of the OD process suitable to the various influent conditions, such as a counterplan to alleviate excess low loading, a variant water depth operation, etc. are explained by the full-scale examples.

Effects of temperature and volatile fatty acids on nitrification-denitrification activity in small-scale anaerobic-aerobic recirculation biofilm process

The purpose of this study is to clarify effects of temperature, volatile fatty acids (VFAs) and recirculation on nitrification-denitrification activity and biota such as nitrifying bacteria in a small-scale domestic wastewater treatment process. Effects of VFAs produced in anaerobic biofilm reactors under various flow-rates and recirculation ratios on nitrifying bacteria were also investigated with laboratory-scale plants on a long-term stable conditions. As a result, at a temperature of 10°C, nitrification activity could be increased about 65% by recirculation and nitrogen removal efficiency was also surely raised. Temperature coefficients of nitrification rate at recirculation ratios of 0 and 4.0 were 1.039 and 1.090, respectively, and that of denitrification was 1.065 at recirculation ratio of 4.0. High concentrations of VFAs were found in anaerobically treated effluent, especially at 10°C without recirculation, and inhibition of nitrite oxidation and nitrite accumulation were observed in the aerobic biofilm reactor. From batch experiments, VFAs' inhibition constants γ in nitrification activity of aerobic biofilm was calculated, and consumption rates of each VFA was investigated on the condition that denitrification was progressed or not. It was clarified that each VFA did not inhibit ammonium oxidation in observed concentration, but slightly inhibited nitrite oxidation. Acetic acid was used as a carbon source of denitrification at the rate of 17.3mg/mg-SS/hr. On the other hand, propionic acid was not used effectively and denitrification did not occur. It was concluded that the recirculation was indispensable to promote nitrification-denitrification activity and biodegradation of VFAs in the small-scale anaerobic-aerobic biofilm process.

Effects of temperature and volatile fatty acids on nitrification-denitrification activity in small-scale anaerobic-aerobic recirculation biofilm process

The purpose of this study is to clarify effects of temperature, volatile fatty acids (VFAs) and recirculation on nitrification-denitrification activity and biota such as nitrifying bacteria in a small-scale domestic wastewater treatment process. Effects of VFAs produced in anaerobic biofilm reactors under various flowrates and recirculation ratios on nitrifying bacteria were also investigated with laboratory-scale plants on a long-term stable conditions. As a result, at a temperature of 10°C, nitrification activity could be increased about 65% by recirculation and nitrogen removal efficiency was also surely raised. Temperature coefficients of nitrification rate at recirculation ratios of 0 and 4.0 were 1.039 and 1.090, respectively, and that of denitrification was 1.065 at recirculation ratio of 4.0.High concentrations of VFAs were found in anaerobically treated effluent, especially at 10°C without recirculation, and inhibition of nitrite oxidation and nitrite accumulation were observed in the aerobic biofilm reactor. From batch experiments, VFAs' inhibition constants γ in nitrification activity of aerobic biofilm was calculated, and consumption rates of each VFA was investigated on the condition that denitrification was progressed or not. It was clarified that each VFA did not inhibit ammonium oxidation in observed concentration, but slightly inhibited nitrite oxidation. Acetic acid was used as a carbon source of denitrification at the rate of 17.3mg/mg-SS/hr. On the other hand, propionic acid was not used effectively and denitrification did not occur. It was concluded that the recirculation was indispensable to promote nitrification-denitrification activity and biodegradation of VFAs in the small-scale anaerobic-aerobic biofilm process.

The Significance of Small Scale Domestic Wastewater Treatment System

The Significance of Small Scale Domestic Wastewater Treatment System

The use of a zeolite-iron column for residual ammonia and phosphorus removal in the effluent from a membrane process as an on-site small-scale domestic wastewater treatment

Laboratory-scale experiments were performed to investigate the performance of the on-site small-scale combined system of membrane separation bioreactor (MSB) and zeolite-iron (Z-Fe) column. Average nitrogen removal by the membrane separation bioreactor was varied from 83% at an influent nitrogen concentration of 30 mg/l to 50% at 75 mg/l. Residual ammonia nitrogen in the effluent from the membrane separation bioreactor was further polished by a Z-Fe column to an initially non-detectable concentration and finally to 1.2 mg/l. The average phosphorus removal by this column unit was 70%. Improvement by providing aeration to the bottom part of iron bed in the long column improved phosphorus removal efficiency to as much as 92% until water logging occurred inside the column. Moreover, further improvement was achieved by inserting three short columns in series for 116 day of operation. Average effluent phosphorus concentrations of 1.2, 0.39 and 0.16 mg/l were obtained after the 1st, 2nd and 3rd column respectively with an applied influent phosphorus concentration of 5.3 mg/l on average. Furthermore, batch experiments were carried out to investigate the factors, such as pH and temperature, which affect the performance of the Z-Fe column in phosphorus removal.

Simultaneous removal of carbonaceous and nitrogenous pollutants by a plunging liquid jet bioreactor with crossflow filtration operated under intermittent aeration

Simultaneous removal of total organic carbon (TOC) and nitrogen (T-N) by a plunging liquid jet bioreactor was investigated for small-scale treatment of domestic wastewater. The bioreactor was operated under suspended growth and attached growth conditions and intermittent aeration to carry out both nitrification and denitrification processes in one vessel. In the suspended growth system, TOC removal efficiency was about 90% but nitrogen removal was about 50%. The nitrogen removal was not sufficient because nitrification was a rate-limiting step. To overcome this limitation, a biomass carrier was inserted in the reactor. In the attached growth system, nitrification proceeded almost completely and, hence, nitrogen removal was increased. TOC and nitrogen removal efficiency was 97% (effluent TOC concentration was about 3·0 mg/l) and 84% (effluent T-N concentration was about 2·0 mg/l) in the oxic periods, respectively, and those were 93% (TOC concentration was about 5·5 mg/l) and 90% (T-N concentration was about 1·2 mg/l) in the anoxic periods. This effluent T-N concentration satisfies the severest target value for T-N discharge concentration in small-scale domestic wastewater treatment in Japan. The bioreactor system with the biomass carrier operated under intermittent aeration was judged to be excellent for simultaneous removal of TOC and nitrogen in small-scale treatment of domestic wastewater.

The use of a zeolite-iron column for residual ammonia and phosphorus removal in the effluent from a membrane process as an on-site small-scale domestic wastewater treatment

Laboratory-scale experiments were performed to investigate the performance of the on-site small-scale combined system of membrane separation bioreactor (MSB) and zeolite-iron (Z-Fe) column. Average nitrogen removal by the membrane separation bioreactor was varied from 83% at an influent nitrogen concentration of 30 mg/l to 50% at 75 mg/l. Residual amnionia nitrogen in the effluent from the membrane separation bioreactor was further polished by a Z-Fe column to an initially non-detectable concentration and finally to 1.2 mg/l. The average phosphorus removal by this column unit was 70%. Improvement by providing aeration to the bottom part of iron bed in the long column improved phosphorus removal efficiency to as much as 92% until water logging occurred inside the column. Moreover, furher improvement was achieved by inserting three short columns in series for 116 day of operation. Average effluent phosphorus concentrations of 1.2, 0.39 and 0.16 mg/l were obtained after the 1st, 2nd and 3rd column respectively with an applied influent phosphorus concentration of 5.3 mg/l on average. Furthermore, batch experiments were carried out to investigate the factors, such as pH and temperature, which affect the performance of the Z-Fe column in phosphorus removal.

Anaerobic and Aerobic Submerged Bio-Filter System for Small Scale On-Site Domestic Sewage Treatment

In order to prevent water pollution and satisfy the demands for flush toilets in regions where a public sewerage system has not been in service, some on-site small scale domestic wastewater treatment processes called GAPPEI JOHKASOU have been developed to treat black water and gray water together in an individual house. Prior to its technical development, the characteristics of wastewater discharged from individual houses should be measured. The possibility of application of anaerobic filter is examined for processing organic wastewater at low concentration like in domestic wastewater, and an anaerobic filteris successfully developed to lengthen the sludge removal interval, since the flow rate of wastewater from individual houses is characterized by a large variation. It is difficult to serve the centralized treatment systems in many regions. Thus, a small GAPPEI JOHKASOU has been developed and propagated for by individual houses in such regions.