Assessment of Biological Trickling System with Different Layers of Material for Grey Water Treatment

Greywater reuse is an attractive alternative whenever water resources are scarce because it can lower water demand and increase available water supply. This study used simple, easy-to-find treatment and purification methods to examine how gray sewage from homes could be used in agriculture. The primary motivation for reducing agricultural fertilizer consumption is financial gain. If feasible, society can achieve more acceptable economic objectives. The multimedia biofilter, a biological trickling filter, treats wastewater biologically by attaching biomass to various media. In this investigation, raw greywater was settled for two hours. The same influent was used to compare and contrast two treatment approaches. The treatment methods include an exploration of the effectiveness of two filters. The first filter comprises sand, gravel, cotton, and activated carbon filtration layers. The second contains sand, gravel, brick bat, wood chips, and rice husk filtration layers. Gray water was purified utilizing a sand filtration system (gravel and sand), along with the addition of other materials to improve the effectiveness of the treatment. These additional materials included cotton, active carbon, brick, wood chips, and rice husks. Chemical tests were performed on the graywater, and each component was identified. Overall, the sand-gravel-cotton-activated carbon filter improved greywater quality to irrigation standards by reducing organic matter. The second filter (made of sand, gravel, brick, wood chips, and rice husks) is a low-cost greywater recycling unit. But there is still room for improvement in how well these filters work with higher and changing loads and how long their materials last. As a result, most of the filter materials used were waste products generated inside homes and are said to be the least expensive and most inexpensive filters.


Introduction
Grey water is frequently called wastewater produced in the kitchen, laundry, and bathroom.Aside from toilet waste, all water draining from the home is greywater [1].In developing nations, there are more options for greywater reuse due to increasing industrialization and development [2,3].The amount of greywater produced by a population is determined by its overall water use, the standard of living, demographics (such as age and gender), resident behaviors, and water infrastructure [4,5].Hence, between 50% and 80% of the wastewater volume generated by households is made up of greywater.The average amount of greywater is 90 to 120 l/p/d [6].The literature indicates that the kitchen sink and dishwasher account for around 27% of greywater.The washbasin, bathroom, and shower account for about 47%, and the laundry and washing machine account for about 26% [5,7].Grey water is produced as a result of the residents' lifestyle choices [8,9].As a reason, its properties are very variable and impacted by the residents' lifestyles, their social and cultural interactions, water availability, and their consumption level [10].Greywater contains various organic materials, suspended particles, heavy metals, inorganic ions, and E. coli [10,11].Although these pollutants are believed to be present in lower quantities in greywater than in wastewater, numerous investigations have found the contrary to be true.[12] Greywater has a lot of different qualities that change with the time of day, the season, and the amount and quality of the water.Four requirements should be met for gray water reuse and reclamation: aesthetic appeal, hygienic security, financial viability, and environmental toleration [13].The various reuse uses demand different treatments [14,15], from basic to more sophisticated ones, because they have varied requirements for water quality.Integrating an aerobic biological process with physical filtration is the most efficient and practical way to treat greywater.The biological trickling filter, part of the multimedia biofilter, is a good choice for urban residential buildings [16].Sand infiltration is the technique for greywater treatment used most frequently [17].Sand filters have several challenges, including clogging, a shortage of adequately graded sand in certain places, and high transportation expenses as a result of the higher bulk density [18,19].To lower biochemical oxygen demand (BOD5), nutrients, surfactants, chemical oxygen demand (COD), and microbiological contaminants, alternate materials, including sand layers, wood chips, brick, and activated charcoal in multimedia biofilters, need to be researched.These materials should typically have adequate physicochemical properties and a low bulk density to facilitate handling and transportation.Few studies have been done on how to lower COD and BOD5 with bio-carriers like activated carbon, wood chips, and rice husks.Still, none of them have directly mentioned the production of irrigation water.Activated carbon, wood chips, and rice husks all appear to have a high ability to reduce BOD5 and COD, making them attractive for greywater treatment [20,21].Moreover, activated carbon, wood chips, and rice husks have been investigated to adsorb various contaminants, such as heavy metals and aromatic hydrocarbons [22,23].More research needs to be done to find out how well these materials can remove organic matter from greywater so that it can be used for irrigation.Given their physical properties (specific surface area and effective size), filters' behavior during startup and the steady state must be researched.This is necessary to comprehend how the filter reduces pollutants and subsequently construct (at a later stage) a design model and filter design criteria.The current study aims to assess the household greywater produced by surrounding households and the requirement for creating a treatment system to preserve water.Usually, the need to reduce costs is the main factor in design decisions [24].Simpleness, easily accessible resources, and low maintenance are among the Middle Eastern nation's guiding ideals [14,25,26].Some of the organic and inorganic pollutants present in greywater, including Chemical Oxygen Demand (COD), Oil, Turbidity, Calcium, Magnesium, Sodium, and Chloride, are reduced by using indigenous Iraqi materials like "sand, gravel, cotton, activated carbon, brick, wood chips, and rice husks" as filter media.This study aimed to assess and compare the reduction of BOD5, turbidity, COD, TDS, phosphate, nitrogen, and certain microorganisms in greywater caused by several multimedia biofilters.The primary objective is to assess suitable small-scale greywater treatment filters in order to consider providing water for agricultural irrigation.

Study Area Description
In this study, different homes in Baghdad City, Iraq, were selected as a case study for collecting the greywater that flowed from a bathroom, laundry, washbasin, and kitchen sink.

Greywater characterization and collection
Several greywater sources were found, including a kitchen sink, washbasin, post-shower water, and laundry water.After being disconnected from the primary wastewater collecting stream, drain pipes from these sources were made to flow independently into separate 5-liter containers.The research was done to characterize the different sources of greywater-each of the aforementioned greywater generation locations.Samples were taken from the collecting tanks and then examined in a lab to determine the levels of various parameters, including pH, COD, BOD, turbidity, and TSS.

Sample analysis
Before and after the treatment, samples were analyzed to examine the various greywater qualitydetermining parameters.Prior to treatment, 1-liter samples from diverse sources were collected and tested using standard Methods procedures for variables like pH, turbidity, TSS, COD, BOD, and chlorine [27].A COD digester was used to measure the COD.

Treatment method
Gray water must be treated before being stored and used.Gray water might be treated to a higher quality before reuse since reusing it if it has not been treated will be harmful to human health, the environment, and both [14,28,29].In order to comply with reuse regulations, treatment must solve the esthetic, health, and technical issues that organic waste, bacteria, and solids might cause [14].The treatment of gray water has been the subject of numerous investigations using various complicated and performant methods [10].This study used a multimedia biofilter to treat the gray water, using multiple materials, including cotton, active carbon, brick, wood chips, rice husks, and sand and gravel layers.

Experimental setup
The schematic design in Fig. 6 depicts the treatment train.The following three treatment approaches were examined: • The first unit does not use chemicals, settling the greywater in the settling tank.Greywater can remain in the basin since most suspended contaminants tend to settle down by gravity.This process is known as plain sedimentation.Which refers to the process whereby impurities (the distinct particles) are separated from the fluid by the influence of natural forces.The basin where the greywater is held is called a settling basin, sedimentation basin, or clarifier.In addition, the detention period defines the average amount of time the greywater is contained in the tank.• The second unit is the collection tank .A submersible pump with a discharge capacity of 1400 L/hr flow and 2.8 m head transfers greywater from the sump to the filter system through distribution piping, as shown in Fig. 6.The filter container is a typical plastic sand filter with a 15-to 50-cm high diameter and was used to treat gray water.The first filter (filter no. 1) has six layers of activated carbon, cotton, sand, and gravel with different gradations.The second filter (filter no. 2) has six layers of wood chips, rice husks, brick, gravel, and sand.They were utilized to select the filter's dimensions and characteristics for laboratory testing.Each layer had a 5 to 10-cm height, and the setup had a tank at the top for collection tanks.Figure 6 depicts the control valves of the treatment system for water entry into the filter.A cylindrical tank for collecting water after filtration made up the second piece of equipment.

Procedure of the operation runs
Greywater was collected in a sedimentation tank and allowed to sediment for 1 to 2 hours before being piped to an elevated storage tank.The greywater is transferred to the filter columns (filters no. 1 and 2) from the storage tank, each controlled by a gate valve.Each filter's influent filtration rates are kept constant.It suggested employing a constant rate filtration technique for the pilot filter unit [29].The effluent valve was continuously adjusted to maintain the required flow rate throughout each run.The effluent samples collected by the effluent valves are analyzed at specific points throughout the run.

Characterizing raw greywater
Analysis was done on TSS, BOD, COD, chlorine concentration, turbidity, and pH.The average characterization values for several parameters are shown in Table 2.The COD and BOD values were found to be greater than those of any prior research.The pH ranged from 7.2 to 8.5, and the turbidity levels were very high.Even when the source is the same, the major variance in greywater quality must 3.

Treatment system performance and effectiveness
The various characteristics of filters 1 and 2 after treatment are shown in Tables 3 and 4. The analyzed parameters had high readings before the treatment process.The values of the tested parameters decreased, demonstrating the effectiveness of the filter layers in the treatment.Greywater generation and properties vary significantly depending on the source [30].The criteria define greywater changes according to the season or time of year.This change happens due to moisture content, temperature, microbial growth, etc.The greywater samples' BOD significantly decreased in the winter.In low temperatures, microbial growth may be inhibited, which might cause this.Greywater cannot be reused since it lacks any treatment, even if it is less filthy than blackwater.All of the filter layers showed a minimum removal effectiveness of 75%.The coupled filter units have a higher capacity for removal.Gray water treatment utilizing various materials improved some of the qualities.So far, after treatment, specific values have taken on more significance.There were no especially high results, and the majority of the readings were within the acceptable levels for agricultural water usage.

A comparison of the two filters treatments
Eight samples of each type of treated water were used in the testing.Figures 7 and 8 show that the treated grey water achieved results in the treatment of the turbidity and COD parameters, which are among the acceptable determinants for the reuse of grey water for agricultural purposes, noting that the removal reduction in the first filter is greater than that in the second filter.

Conclusions
The described multimedia bio-sand filters can be used in many places, such as single-family homes, large businesses, and small villages.The cost of running wastewater treatment plants decreases when grey and blackwater are kept separate.The simple, readily available, and reasonably priced materials produced positive outcomes.Most of the applications for this greywater are in agriculture, and the results did not indicate a material difference in the chemical treatment.Greywater's total fecal coliforms, T-P, BOD5, COD, and other physical, chemical, and biological characteristics were all within acceptable ranges.They had no negative effects on the soil or plants.It is a desirable low-cost solution for treating greywater in the home due to the accessibility of natural, low-cost materials and the ease of the treatment method (filtration).Grey water that has been treated using natural resources is a good substitute for fresh water in the production of plants.Compared to irrigation with treated greywater, irrigation of plants with greywater without treatment will raise the soil's pH, EC, and other characteristics.In general, the first filter with sand, gravel, cotton, and activated carbon is the best at removing organic matter from greywater and seems to be the one that could be used for irrigation.The second filter of sand, gravel, brick, wood chips, and rice husks is a low-cost greywater recycling unit.The longevity of the filter materials and the efficacy of these filters under heavier and more erratic loads still need enhancement.Due to this, most filter materials utilized were waste products created inside the home, making them the least expensive and most inexpensive filters.

Figure 1 .
Figure 1.The percent of greywater produced in the study area.

Figure 2 .
Figure 2. Prepared samples for the laboratory.

4 •
The third unit receives the greywater and transfers it to the filter media via the filter container, as shown in Fig.4.

Figure 3 .
Figure 3. Image of the actual pilot sample designed.

Figure 5 .
Figure 5. Schematic diagram of the set (Flow diagram).

Table 1 .
Greywater production in the study area.