Treatment of Mixer Truck Wash Water of a Ready-mix Concrete Batching Plant Using a Low Cost Modified Sand Filter

Abstract

ABSTRAK Pembangunan infrastruktur dan perumahan membutuhkan beton dalam jumlah besar, yang sebagian dipasok oleh pabrik beton siap pakai. Tingginya kebutuhan air dan produksi air limbah oleh industri ini menyebabkan masalah lingkungan yang signifikan. Sebuah pabrik beton di Bali mengolah air limbahnya dengan lima kolam sedimentasi sederhana yang dilengkapi dengan saringan ijuk antar kolam dan kemudian air hasil olahan dibuang ke hutan bakau di sekitarnya. Meskipun nilai Chemical Oxygen Demand (COD) telah diturunkan dari 316,149 mg/L menjadi 146 mg/L, air limbah ini masih berpotensi merusak biota hutan bakau. Padahal, air bisa didaur ulang untuk membersihkan peralatan atau bahkan menjadi air proses. Penelitian ini bertujuan merancang proses pengolahan yang sederhana dan murah beserta peralatannya. Air limbah yang berasal dari bak pengendapan di pabrik beton siap pakai diolah di laboratorium menggunakan tawas tetapi hasilnya tidak memuaskan sehingga dipilih metode fisika dengan menggunakan kolam sedimentasi dan saringan pasir lambat yang dimodifikasi, dan berhasil menurunkan nilai COD sebesar 82,83% pada pH 12,27 dan mendaur ulang 84% air limbah atau 26,7% kebutuhan air total industri ini. Kata kunci: pengolahan air limbah, beton siap pakai, desain bangunan, daur ulang air ABSTRACT Infrastructure and housing developments require vast quantities of concrete, which are supplied by the ready-mix concrete (RMC) batching plant. This industry's high water demand and wastewater generation have caused significant environmental problems. An RMC batching plant in the southern part of Bali produces liquid waste, which is disposed of into the surrounding mangrove forests after being treated using five sequential unlined wash water ponds and palm fibre. Although the COD value has been decreased from 316.149 mg/L of untreated wastewater to 146 mg/L after treatment, this still has the potential to harm the mangrove biota. On the other hand, the water can still be reclaimed for cleaning purposes or even incorporated into process water. The work aims to design a low cost and simple wastewater recycling process and equipment. Wastewater was collected from the existing settling basin at the RMC batching plant and treated in the laboratory. It was found that the chemical treatment of wastewater using alum did not produce satisfactory results; therefore, a physical method was chosen by employing a sedimentation pond and a modified slow sand filter. It removed 82.83% of the COD at pH 12.270 and reclaimed 84% wash water or 26.7% of total water needed for this industry. Keywords: wastewater treatment, ready-mix concrete, building design, water recycles

Wastewater Characterization and pH Neutralizing Effect of Adsorbents: A Case Study of Washed Concrete Wastewater from a Ready-Mix Plant

“…The concentra- tions were far below the standard. Accordingly, other studies related to washed concrete wastewater also measured the concentration of heavy metals such as cadmium, mercury, copper, zinc, chromium, and lead in the wastewater (Ciawi et al, 2022;Mohamed et al, 2015b;Vaičiukynienė et al, 2021). With the exception of chromium and lead, the concentration of most heavy metals from the aforementioned studies was also low, which is similar to the obtained result of this study.…”

“…The treatment of concrete wash wastewater has three main objectives which are to neutralize pH, decrease turbidity, and eliminate pathogens (De Paula et al, 2014). Several treatment methods have been developed and implemented to carry out this treatment process, including the use of sedimentation tanks and the addition of HCl to reduce pH level (Tsimas and Zervaki, 2011), coagulation and aluminium sulphate addition for pH level reduction (De Paula et al, 2014, slow sand filter (Ciawi et al, 2022;Ghrair et al, 2020a), as well as barium chloride and disodium hydrogen phosphate treatment (Mohamed et al, 2015a). These treatment methods can be classified into three groups namely sedimentation, chemical addition, and filtration.…”